Aircraft vs. RLV design philosophy (X-15, Atlas cost comparison)
mlin...@my-dejanews.com
I found an old AAS article from 1969, written by a Convair guy
named Frank Dore ("AIRCRAFT DESIGN AND DEVELOPMENT
EXPERIENCE RELATED TO REUSABLE
LAUNCH VEHICLES"). It's an excellent summary of the
way Len Cormier, Pat etc. reason and I initially found it
rather convincing. Having thought about it for a little
longer, I'm not quite so sure, though...
---
Dore compared the development cost of the X-11 Atlas A
prototype to that of the X-15. His argument was that both
vehicles are roughly comparable since they were "first
of its kind" type of projects, roughly the same size and
from the same time period (1950s). The development
costs (less engines) were as follows:
Non- Recurring Cost
recurring cost
Atlas 108.6 + 148.3 = 256.9M
X-15 56.9 + 7.4 = 104.3M
Production cost per vehicle:
Atlas $2.8M
X-15 $8.0M
Atlas DDT&E cost breakdown:
Mass Cost Cost/lb
Structure 5279lb $11.64M $2200/lb
Hydraulics 1249lb $17.40M $14000
Propulsion integration 856lb $11.49M $13400
Autopilot 337lb $17.10M $50800
Electrical system 520lb $6.16M $11900
Instrumentation 1769lb $7.84M $4400
---------------------------------------------------------------------
X-15 DDT&E cost breakdown: not available...
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
This is the first time I have seen *ANYONE* dig up some
figures to support their claims that RLVs "ought to be
just as simple as aircraft". Dore's conclusions from the
above data are:
-The cost difference between aircraft and spacecraft
is a factor of ten or more, although modern jet
aircraft usually are more complex, fully reusable,
require only a minimum of maintenance and operate
in a rather challenging environment.
-The difference can be explained because aircraft
can be incrementally tested, are designed for
redundancy and have a pilot on board
that can fix errors. For example, the X-15's initial success
ratio after 47 flights was 96% vs. 60% for the first 47
Atlas launches. The test flights did uncover some design
flaws, but they could be fixed relatively easily.
An Air Force study concluded that
the X-15's success ratio would have been comparable
if the vehicle had been non-redundant an unmanned.
For the Atlas, the most expensive item was the automatic
GN&C system.
-The high cost of expendables is mostly tied to stringent
Q&A, since any manufacturing or operational error likely
results in a failed mission. New ELVs are typically declared
operational after only 2-6 flights, each of which takes the
ELV to the limits of the expected flight environment (orbital
launch). Consequently the Atlas required 100,000 man-hours
for checkout, gradually decreasing to 10,000 man-hours.
-For jet aircraft, the maintenance "learning curve" is much
steeper, typically going from 10,000MH to 10-100MH as
the flight test program progresses. This is because there
is a familiarity and confidence in systems that have been
tested, reused and proven capable. Aircraft typically
perform 300-1000 test flights before they are declared
operational.
-Admittedly, an orbit-capable RLV will be complex since
it has to be big and fly to high altitudes and speeds. Dore
argues that high-performance supersonic military aircraft
ought to be more complex because of the strong coupling
between aerodynamic efficiency over a wide Mach number,
propulsion and structural efficiency. In contrast, a "simple" RLV
has a negligible aerodynamic drag problem, the only
significant structural requirement is related to the tank
pressure and the rocket engine performance is not
affected by the aerodynamics of the vehicle.
-As an example of this, Dore (using the RAND costing
method) claims that the X-15 would
have cost three times as much if if it were an airbreathing
Mach 5-6 aircraft designed to military specs. He also
argues that super/hypersonic airbreathing RLV boosters
don't seem very promising for this reason.
-Finally, Dore applies the "lessons learned" to Convair's
$1B "Triamese" TSTO project and predicts a factor of 50
launch cost reduction from existing ELVs... The Triamese
should be based on proven concepts & technologies
from aviation & space developments. It should: 1) permit
incremental testing, 2) be manned and be abortable,
3) its engines and systems should be
designed for multiple flights and easy maintenance,
4) the aerodynamics should be simple (low L/D) to avoid
heating problems etc.. and 5) it should only fly simple
short duration missions carrying a small payload.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Any comments on this? My reservations are:
1) Dore apparently dismissed the difficulty of
developing high performance reusable subsystems,
particularly related to propulsion and TPS. This is
strange, because the X-15 cost a fortune per flight
($0.27M in '67 dollars). Its maintenance cost was as
high as Dore's prediction for the Triamese, despite
the fact the X-15 was far smaller, consisted of
only a single vehicle and did not fly as
high or as fast! If incremental flight testing is supposed
to be the cure to all problems, how does it allow you
to develop an SSME or TPS much more cheaply? The former
can be tested just as well on the ground, while the latter
requires Mach 15 or better.
2) Incremental testing might not always be as simple
for vertically launched multistage vehicles such as the
Triamese, and pilots probably would find it rather difficult
to control such vehicles manually. Even the X-15 lost a
craft due to pilot error. The Triamese would have featured
jet engines for landing & flight tests, but the weight penalty
of that is usually deemed excessive. Most RLVs perform
unpowered horizontal or rocket-powered vertical landings
which are riskier and more difficult.
3) One also has to
factor in the cost of a flight test program of an RLV
based on today's high-performance propulsion. The SSME
requires significant and expensive refurbishment per flight.
Russian engines? The Energia's RD-0120 LOX/LH2 engine
has a lifetime of just five missions, while the Saturn V's
F-1, J-2 and Zenit RD-170 are rated for ten flights. Finally,
the NK-33 used by Kistler is good for twenty flights. Each
of these engines costs $5-30 million in today's dollars.
While KellySpace and Pioneer undoubtedly will use "aircraft
like" incremental testing to some extent, I don't think
they will perform 300-1000 flights before declaring their
vehicles operational...
4) Weight growth proved to be a _major_ problem for the
Shuttle, and it was not possible to keep all the safety
and maintainability-enhancing features in the design.
Dore might be right about the difficulty of sustained
supersonic cruise in the atmosphere, but the requirement
for a far higher mass fraction still complicates RLV
design. Triamese would have required a mass fraction of
about 0.18 or 0.19 which appears like a challenging goal
for a relatively small vehicle.
For these reasons, I tend to believe that the Convair Triamese
would _not_ have achieved its cost goals if it had been based
on early 1970s technologies... It clearly would have been
more successful than the current Shuttle, due to the simpler
design (thrust load paths, aerodynamics etc.) and a far
more restricted mission profile (=no need to act as a
mini-space station, fly extended missions etc.).
---
Despite these reservations, I believe the basic premise is
correct: it is possible to develop launchers that operate
more or less like aircraft without increasing the cost and
complexity too much. If the performance is reduced sufficiently
(DC-X is the prime example), the vehicle can be developed
and operated for costs that appear reasonable by aircraft
standards. For the time being, I am drawing the line
somewhere around Mach 8- or so.
MARCU$
-----== Posted via Deja News, The Leader in Internet Discussion ==-----
http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum
l...@tour2space.com
mlin...@my-dejanews.com wrote:
> Scavenging my library,
> I found an old AAS article from 1969, written by a Convair guy
> named Frank Dore ("AIRCRAFT DESIGN AND DEVELOPMENT
> EXPERIENCE RELATED TO REUSABLE
> LAUNCH VEHICLES"). It's an excellent summary of the
> way Len Cormier, Pat etc. reason and I initially found it
> rather convincing. Having thought about it for a little
> longer, I'm not quite so sure, though...
>
> ---
>
Very interesting, Marcus. What can I say? Except that
you just got some more points in my bood for being
open-minded.
Incremental testing is extremely important. I mentioned
some time ago in another post that as a project engineer
at North American (LA Div) I inherited a resuable Atlas
project that Rocketdyne had gotten GD to look at -- and
later (1962) us. I understand that GD kept going over their
numbers because development costs seemed so low. I
maintain that incremental flight test pulls the rug out
from under the necessity for extremely expensive QA and
the need to live with a few handwringing tests. This
changes the whole cost culture of the project.
> -The high cost of expendables is mostly tied to stringent
> Q&A, since any manufacturing or operational error likely
> results in a failed mission. New ELVs are typically declared
> operational after only 2-6 flights, each of which takes the
> ELV to the limits of the expected flight environment (orbital
> launch). Consequently the Atlas required 100,000 man-hours
> for checkout, gradually decreasing to 10,000 man-hours.
>
> -For jet aircraft, the maintenance "learning curve" is much
> steeper, typically going from 10,000MH to 10-100MH as
> the flight test program progresses. This is because there
> is a familiarity and confidence in systems that have been
> tested, reused and proven capable. Aircraft typically
> perform 300-1000 test flights before they are declared
> operational.
>
> -Admittedly, an orbit-capable RLV will be complex since
> it has to be big and fly to high altitudes and speeds. Dore
> ....
A TSTO RLV can offer enormous relief in this regard
relative to an SSTO RLV.
> ...argues that high-performance supersonic military aircraft
As you point out, avionics is the big item -- and
things have changed a lot on this front.
Also, with regard to the benefits of incremental testing
on TPS and engine (not SSME) development, incremental
testing will allow you to approach the heating and
pressure cycling of the TPS rather economically. If we
can fly the booster out of the atmosphere for a few tens
of thousands of dollars per flight, we expect to use it as
a test bed for engine module development. For orbiter
testing -- and full heating testing of the TPS -- we
can fly the two-stage system on appropriate suborbital
and orbital flights at perhaps $125,000 per flight for
flying part of the test (excluding test instrumentation,
data reduction, etc,).
> 2) Incremental testing might not always be as simple
> for vertically launched multistage vehicles such as the ...
Hey -- one of the reasons why I like HTOL.
> ... Triamese, and pilots probably would find it rather difficult
> to control such vehicles manually. Even the X-15 lost a
> craft due to pilot error. The Triamese would have featured
> jet engines for landing & flight tests, but the weight penalty
> of that is usually deemed excessive. Most RLVs perform
> unpowered horizontal or rocket-powered vertical landings
> which are riskier and more difficult.
>
Our booster makes powered flyback and approach and landing
with airbreathing engine out -- even with an empty orbiter still
on board. The orbiter is dead stick, but approaches and
lands more like a higher-performance light plane without
an engine or fuel (with quite limited damage potential BTW).
The idea of landing vertically with a precisely and limited
amount of rocket propellants scares the hell out of me.
> 3) One also has to
> factor in the cost of a flight test program of an RLV
> based on today's high-performance propulsion. The SSME
> requires significant and expensive refurbishment per flight.
> Russian engines? The Energia's RD-0120 LOX/LH2 engine
> has a lifetime of just five missions, while the Saturn V's
> F-1, J-2 and Zenit RD-170 are rated for ten flights. Finally,
> the NK-33 used by Kistler is good for twenty flights. Each
> of these engines costs $5-30 million in today's dollars.
> While KellySpace and Pioneer undoubtedly will use "aircraft
> like" incremental testing to some extent, I don't think
> they will perform 300-1000 flights before declaring their
> vehicles operational...
As much as I think sticking with off the shelf engines
and equipment is extremely important, the high cost of
existing rocket engines causes me (and Gary) to look toward
new (hopefully simple, straightforward) rocket engines.
People like John Hare think the the pump problem can be
solved as an MCD project. Data points already exist with
respect to low-cost, pressure-feds. According to Del
Tischler, the V-2 used an off-the-shelf water pump for
pumping the oxidizer.
>
> 4) Weight growth proved to be a _major_ problem for the
> Shuttle, and it was not possible to keep all the safety
> and maintainability-enhancing features in the design.
> Dore might be right about the difficulty of sustained
> supersonic cruise in the atmosphere, but the requirement
> for a far higher mass fraction still complicates RLV
> design. Triamese would have required a mass fraction of
> about 0.18 or 0.19 which appears like a challenging goal
> for a relatively small vehicle.
>
I am scared of weight growth too, Marcus. That's one of the
reasons why I believe that TSTO is the place to start. Our
orbiter mass fraction (with pilot and payload subtracted
from gross mass) is 0.14 -- which I agree is very challenging
for a small vehicle. We are also using a low delta vee booster.
Staging at higher mach than 2.5 or 3 (at low dynamic pressure)
could make up for some slippage. Also, a small vehicle allows
the project team to concentrate on fewer details to reduce
empty mass. Subsystems are not only relatively less costly now,
but also much lighter (especially avionics). Our big feasibilty
point will be proof of our TPS, which can be proven (or disproven)
for perhaps $500,000.
You might say that the Shuttle is not single-stage either.
However, the basic design concept for the Shuttle, is, and
always has been, absurd -- except, perhaps, the political
point of view, where it is inspired.
> For these reasons, I tend to believe that the Convair Triamese
> would _not_ have achieved its cost goals if it had been based
> on early 1970s technologies... It clearly would have been
> more successful than the current Shuttle, due to the simpler
> design (thrust load paths, aerodynamics etc.) and a far
> more restricted mission profile (=no need to act as a
> mini-space station, fly extended missions etc.).
>
> ---
>
> Despite these reservations, I believe the basic premise is
> correct: it is possible to develop launchers that operate
> more or less like aircraft without increasing the cost and
> complexity too much. If the performance is reduced sufficiently
> (DC-X is the prime example), the vehicle can be developed
> and operated for costs that appear reasonable by aircraft
> standards. For the time being, I am drawing the line
> somewhere around Mach 8- or so.
>
Actually, I draw the line for booster airframe design at
about mach 3, and for airbreathing engines (in the booster)
at about mach 0.8. The orbiter does have to glide back through
reentry (with much reduced heating due to low planform
loading). Except for the TPS, the orbiter does not see
much of reentry temperatures.
Getting close to aircraft costs with RLVs is a very
important goal. On the basis of total energy, space
launch costs are perhaps three orders of magnitude
greater than global transport with an efficient
subsonic transport.
I'm glad that you are willing to admit that there
may be something to the arguments that some of us
RLV'ers are trying to make.
> MARCU$
>
Best regards,
Len (Cormier) for MMI
l...@tour2space.com ( http://www.tour2space.com )
clb...@my-dejanews.com
> I found an old AAS article from 1969, written by a Convair guy
> named Frank Dore ("AIRCRAFT DESIGN AND DEVELOPMENT
> EXPERIENCE RELATED TO REUSABLE
> LAUNCH VEHICLES"). It's an excellent summary of the
> way Len Cormier, Pat etc. reason and I initially found it
> rather convincing. Having thought about it for a little
> longer, I'm not quite so sure, though...
>
> -The difference can be explained because aircraft
> can be incrementally tested, are designed for
> redundancy and have a pilot on board
> that can fix errors. For example, the X-15's initial success
> ratio after 47 flights was 96% vs. 60% for the first 47
> Atlas launches. The test flights did uncover some design
> flaws, but they could be fixed relatively easily.
> An Air Force study concluded that
> the X-15's success ratio would have been comparable
> if the vehicle had been non-redundant an unmanned.
> For the Atlas, the most expensive item was the automatic
> GN&C system.
> MARCU$
>
> -----== Posted via Deja News, The Leader in Internet Discussion ==-----
> http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum
>
96% success?
Looking at the flight logs in Milton O. Thompson's
book "At The Edge of Space: the X-15 Flight Program"
I get the follwing list of remarks for the 1st 47 flights:
FLT REMARK
--- ------
1 Glide flight, no propellants on board;
Pitch damper failed, PIO during flare and landing
2 Turbo pump case failed; fire in H2O2 compartment,
engine compartment and lower ventral;
flaps only extended 60%
3 Nose gear door failed on landing; fire in engine bay
4 Engine fire and explosion; fuselage structural failure
at instrument bay on landing
5 Good flight
6 Good flight
7 Premature shutdown of upper engine
8 360 deg. roll, 6g turn
9 Roll damper and stable platform failed; first NASA flight
10 Good flight
11 Good flight
12 First air force flight; flown on the center stick
13 Good flight
14 Roll damper failed (reset); normal ventral jettison failed
15 First remote site launch; first M=3 flight; stable
platform inoperative
16 First X-15 flight over 100000ft
17 Good flight
18 Good flight
19 Good flight
20 Alpha cross-pointer hooked up backwards
21 Good flight
22 Engines shut down early, failed to restart
23 Good flight
24 Ventral chuted didn't open
25 Good flight
26 First XLR-99 flight
27 Lower engine shut down and restarted
28 Throttled and restarted XLR-99 engine in flight
29 Upper umber 3 chamber did not start;
Inertial attitudes incorrect
30 Crossfield's last flight
31 First ball nose flight
32 Good flight
33 Last XLR-11 flight (in the X-15)
34 First M=4 flight (for any aircraft);
first ball nose flight on ship #2
35 Relight required; SAS limit cycled;
first Hidden Hills launch
36 Relight required; Pitch damper dropout at
shutdown,reset; Cabin pressure rose to 46kft
37 First launch from Mud Lake; SAS dropout at launch;
Cabin altitude went to 50kft
38 Cabin altitude went to 56kft, suit inflated;
First M=5 flight (of any aircraft)
39 First XLR-99 flight for ship #1
40 Fuel line low light at launch
41 Good flight
42 First ventral off flight
43 First aircraft flight above 200000ft; left
windshield shattered during reentry
44 Good flight
45 First flight above M=6 for any aircraft;
right outer windshield shattered at about
M=2.7 during deceleration
46 All three SAS axes disengaged at launch, reset;
Yaw limit cycle caused downmode to fixed gain
47 Two engine malfunction shutdowns; first emergency
landing at Mud Lake; first uprange landing
So : 1 structural failure (on landing, after engine fire
and explosion)
2 fires on board (incl exploding turbopump)
1 emergency landing caused by engine malfunctions
~5 partial or full engine shutdowns that resulted in
significant undershoot of planned M
I am not taking a position on whether the detailed examination
is better or worse for RLV proponents than the simple 96% figure.
It should be noted that none of the incidents caused loss of
aircraft. The #2 X-15 flew flight #4 (structural failure) on
11/5/59 and flew flight #6 on 2/11/60.
--
-chris bond fluid mechanic at large
l...@tour2space.com
clb...@my-dejanews.com wrote:
> In article <6t13dj$a2f$1...@nnrp1.dejanews.com>,
> mlin...@my-dejanews.com wrote:
> > I found an old AAS article from 1969, written by a Convair guy
> > named Frank Dore ("AIRCRAFT DESIGN AND DEVELOPMENT
> > EXPERIENCE RELATED TO REUSABLE
> > LAUNCH VEHICLES"). It's an excellent summary of the
> > way Len Cormier, Pat etc. reason and I initially found it
> > rather convincing. Having thought about it for a little
> > longer, I'm not quite so sure, though...
> >
> > -The difference can be explained because aircraft
> > can be incrementally tested, are designed for
> > redundancy and have a pilot on board
> > that can fix errors. For example, the X-15's initial success
> > ratio after 47 flights was 96% vs. 60% for the first 47
> > Atlas launches. The test flights did uncover some design
> > flaws, but they could be fixed relatively easily.
> > An Air Force study concluded that
> > the X-15's success ratio would have been comparable
> > if the vehicle had been non-redundant an unmanned.
> > For the Atlas, the most expensive item was the automatic
> > GN&C system.
> > MARCU$
> >
> > -----== Posted via Deja News, The Leader in Internet Discussion ==-----
> > http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum
> >
>
man-in-the-loop and incremental testing early in the game.
Even on operational aircraft,
after a typical aircraft flight, the pilot will note several
mechanical gripes -- only once in a while will this ground
the aircraft for the next flight. But it provides the
opportunity to get everything in good working order and
keep it there. If the next flight were to be unmanned,
it probably would be necessary to fix some of the gripes that
otherwise wouldn't ground the airplane. And, of course,
some of the things that are just gripes might have ended
up with the loss of the aircraft without a pilot.
Also note that these kind of gripes don't make headlines.
Rather, they are only the concern of a few people. Even
history making flights sometimes occur in a much less
formal manner than routine space launches -- if you can
believe Tom Wolfe in the "Right Stuff." And of course,
the Wright Stuff didn't exactly resemble a space launch.
Best regards,
Len (Cormier) for MMI
l...@tour2space.com ( http://www.tour2space.com )
-----== Posted via Deja News, The Leader in Internet Discussion ==-----
Frank Crary
>I found an old AAS article from 1969, written by a Convair guy
>named Frank Dore ("AIRCRAFT DESIGN AND DEVELOPMENT
>EXPERIENCE RELATED TO REUSABLE LAUNCH VEHICLES").
>prototype to that of the X-15. His argument was that both
>vehicles are roughly comparable since they were "first
>of its kind" type of projects, roughly the same size and
>from the same time period (1950s). The development
>costs (less engines) were as follows:
> Non- Recurring Cost
> recurring cost
>Atlas 108.6 + 148.3 = 256.9M
>X-15 56.9 + 7.4 = 104.3M
Err... I'm having a basic addition problem here... Last time
I checked, 108.6 + 148.3 = 256.9, but 56.9 + 7.4 = 64.3
Frank Crary
CU Boulder
pat
mlin...@my-dejanews.com wrote:
> Scavenging my library,
> I found an old AAS article from 1969, written by a Convair guy
Someone from the Missile side of the House, not the Aircraft side of the
house.
> named Frank Dore ("AIRCRAFT DESIGN AND DEVELOPMENT
> EXPERIENCE RELATED TO REUSABLE
> LAUNCH VEHICLES"). It's an excellent summary of the
> way Len Cormier, Pat etc. reason and I initially found it
> rather convincing. Having thought about it for a little
> longer, I'm not quite so sure, though...
>
Well, it's a nice summary of many of my arguments.
> ---
>
> Dore compared the development cost of the X-11 Atlas A
> prototype to that of the X-15. His argument was that both
> vehicles are roughly comparable since they were "first
> of its kind" type of projects, roughly the same size and
> from the same time period (1950s). The development
> costs (less engines) were as follows:
>
> Non- Recurring Cost
> recurring cost
> Atlas 108.6 + 148.3 = 256.9M
> X-15 56.9 + 7.4 = 104.3M
>
Was this a typo above? did you drop a 40? off the recurring ops cost?given
the totals feel right, i'll note the X-15 was half the price of the Atlas.
> Production cost per vehicle:
> Atlas $2.8M
> X-15 $8.0M
>
> Atlas DDT&E cost breakdown:
> Mass Cost Cost/lb
> Structure 5279lb $11.64M $2200/lb
Structure is cheap.
> Hydraulics 1249lb $17.40M $14000
> Propulsion integration 856lb $11.49M $13400
> Autopilot 337lb $17.10M $50800
> Electrical system 520lb $6.16M $11900
>
Controls, electronics and hydraulics are expensive.
> Instrumentation 1769lb $7.84M $4400
> ---------------------------------------------------------------------
>
> X-15 DDT&E cost breakdown: not available...
>
> - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
>
> This is the first time I have seen *ANYONE* dig up some
> figures to support their claims that RLVs "ought to be
> just as simple as aircraft". Dore's conclusions from the
> above data are:
>
sorry, for me, it's just obvious.
> -The cost difference between aircraft and spacecraft
> is a factor of ten or more, although modern jet
> aircraft usually are more complex, fully reusable,
> require only a minimum of maintenance and operate
> in a rather challenging environment.
>
> -The difference can be explained because aircraft
> can be incrementally tested, are designed for
> redundancy and have a pilot on board
> that can fix errors. For example, the X-15's initial success
> ratio after 47 flights was 96% vs. 60% for the first 47
> Atlas launches. The test flights did uncover some design
> flaws, but they could be fixed relatively easily.
> An Air Force study concluded that
> the X-15's success ratio would have been comparable
> if the vehicle had been non-redundant an unmanned.
>
This also was the same conclusions from the Manufacturers studies of the
BOMARCmissile. Henryroutinely cites this, but i guess you've never
believed it
> For the Atlas, the most expensive item was the automatic
> GN&C system.
>
Pilots aren't that expensive.
> -The high cost of expendables is mostly tied to stringent
> Q&A, since any manufacturing or operational error likely
> results in a failed mission. New ELVs are typically declared
> operational after only 2-6 flights, each of which takes the
> ELV to the limits of the expected flight environment (orbital
> launch). Consequently the Atlas required 100,000 man-hours
> for checkout, gradually decreasing to 10,000 man-hours.
>
> -For jet aircraft, the maintenance "learning curve" is much
> steeper, typically going from 10,000MH to 10-100MH as
> the flight test program progresses. This is because there
> is a familiarity and confidence in systems that have been
> tested, reused and proven capable. Aircraft typically
> perform 300-1000 test flights before they are declared
> operational.
>
Yep.
> -Admittedly, an orbit-capable RLV will be complex since
> it has to be big and fly to high altitudes and speeds. Dore
>
but over a single mission profile.
> argues that high-performance supersonic military aircraft
> ought to be more complex because of the strong coupling
> between aerodynamic efficiency over a wide Mach number,
> propulsion and structural efficiency. In contrast, a "simple" RLV
>
Military aircraft need to be able to handle combat manuevers, Mach 2
turns,9G manuevers, all of this down in the thick atmosphere.
> has a negligible aerodynamic drag problem, the only
> significant structural requirement is related to the tank
> pressure and the rocket engine performance is not
> affected by the aerodynamics of the vehicle.
>
> -As an example of this, Dore (using the RAND costing
> method) claims that the X-15 would
> have cost three times as much if if it were an airbreathing
> Mach 5-6 aircraft designed to military specs. He also
> argues that super/hypersonic airbreathing RLV boosters
> don't seem very promising for this reason.
>
and you wonder why len and the others are so skeptical of air-breathing.
> -Finally, Dore applies the "lessons learned" to Convair's
> $1B "Triamese" TSTO project and predicts a factor of 50
> launch cost reduction from existing ELVs... The Triamese
> should be based on proven concepts & technologies
> from aviation & space developments. It should: 1) permit
> incremental testing, 2) be manned and be abortable,
> 3) its engines and systems should be
> designed for multiple flights and easy maintenance,
> 4) the aerodynamics should be simple (low L/D) to avoid
> heating problems etc.. and 5) it should only fly simple
> short duration missions carrying a small payload.
>
>
i don't know enough about Triamese to comment.
> - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
>
> Any comments on this? My reservations are:
>
> 1) Dore apparently dismissed the difficulty of
> developing high performance reusable subsystems,
> particularly related to propulsion and TPS. This is
>
TPS is cheap to develope. You can lab test it easily, wind tunnel test
it,we have 20 years more knowledge on materials since STS.
Engines can also be extensively ground tested.
> strange, because the X-15 cost a fortune per flight
> ($0.27M in '67 dollars). Its maintenance cost was as
> high as Dore's prediction for the Triamese, despite
> the fact the X-15 was far smaller, consisted of
> only a single vehicle and did not fly as
> high or as fast!
The X-15 was flying research flights, so it had a lot of support crew,
it's Ops model wasn't that good. B-52, big crew, multiple abort sites,
large support team. a better ops model would use less structure and
people.
each trajectory was different.
> If incremental flight testing is supposed
> to be the cure to all problems, how does it allow you
> to develop an SSME or TPS much more cheaply? The former
> can be tested just as well on the ground, while the latter
> requires Mach 15 or better.
>
Incremental flight test is for bypassing QA, reducing insurance costsand
verifying assumptions. Flight test is an expensive place to
develope subsystems, it's a IV&V stage.
> 2) Incremental testing might not always be as simple
> for vertically launched multistage vehicles such as the
> Triamese, and pilots probably would find it rather difficult
> to control such vehicles manually. Even the X-15 lost a
> craft due to pilot error. The Triamese would have featured
> jet engines for landing & flight tests, but the weight penalty
> of that is usually deemed excessive. Most RLVs perform
> unpowered horizontal or rocket-powered vertical landings
> which are riskier and more difficult.
>
computer assistance is better. better simulators, better pilot support.
> 3) One also has to
> factor in the cost of a flight test program of an RLV
> based on today's high-performance propulsion. The SSME
> requires significant and expensive refurbishment per flight.
> Russian engines? The Energia's RD-0120 LOX/LH2 engine
> has a lifetime of just five missions, while the Saturn V's
> F-1, J-2 and Zenit RD-170 are rated for ten flights. Finally,
> the NK-33 used by Kistler is good for twenty flights. Each
> of these engines costs $5-30 million in today's dollars.
> While KellySpace and Pioneer undoubtedly will use "aircraft
> like" incremental testing to some extent, I don't think
> they will perform 300-1000 flights before declaring their
> vehicles operational...
>
They only need to verify 3-5 trajectories, far easier then the
300-1000needed to verify atmospheric free flight.
> 4) Weight growth proved to be a _major_ problem for the
> Shuttle, and it was not possible to keep all the safety
> and maintainability-enhancing features in the design.
> Dore might be right about the difficulty of sustained
> supersonic cruise in the atmosphere, but the requirement
> for a far higher mass fraction still complicates RLV
> design. Triamese would have required a mass fraction of
> about 0.18 or 0.19 which appears like a challenging goal
> for a relatively small vehicle.
>
STS was poorly managed.
> For these reasons, I tend to believe that the Convair Triamese
> would _not_ have achieved its cost goals if it had been based
> on early 1970s technologies... It clearly would have been
> more successful than the current Shuttle, due to the simpler
> design (thrust load paths, aerodynamics etc.) and a far
> more restricted mission profile (=no need to act as a
> mini-space station, fly extended missions etc.).
>
well anything would have been better then what we got.
> ---
>
> Despite these reservations, I believe the basic premise is
> correct: it is possible to develop launchers that operate
> more or less like aircraft without increasing the cost and
> complexity too much. If the performance is reduced sufficiently
> (DC-X is the prime example), the vehicle can be developed
> and operated for costs that appear reasonable by aircraft
> standards. For the time being, I am drawing the line
> somewhere around Mach 8- or so.
>
gee marcus, now we just need to be 3 times smarter then you.You used to say
we couldn't do anything better then mach 2+
so we needed to be 12 times smarter then you.
what's up? Are you getting smarter ;-)
mlin...@my-dejanews.com
pat <p...@clark.net> wrote:
> >
> > Non- Recurring Cost
> > recurring cost
> > Atlas 108.6 + 148.3 = 256.9M
> > X-15 56.9 + 7.4 = 104.3M
> >
>
> Was this a typo above? did you drop a 40? off the recurring ops cost?given
> the totals feel right, i'll note the X-15 was half the price of the Atlas.
Yup, it should read "47.4".
> > Despite these reservations, I believe the basic premise is
> > correct: it is possible to develop launchers that operate
> > more or less like aircraft without increasing the cost and
> > complexity too much. If the performance is reduced sufficiently
> > (DC-X is the prime example), the vehicle can be developed
> > and operated for costs that appear reasonable by aircraft
> > standards. For the time being, I am drawing the line
> > somewhere around Mach 8- or so.
> >
>
> gee marcus, now we just need to be 3 times smarter then you.You used to say
> we couldn't do anything better then mach 2+
> so we needed to be 12 times smarter then you.
>
> what's up? Are you getting smarter ;-)
Well, that wasn't a very nice comment. Even with a smiley.
---
My argument has never been that we could not do anything better
than Mach 2, technologically speaking. We've already had the
X-15 going to Mach 6, and the Shuttle/Buran to Mach 25. While
it indeed has been obvious to me for a long time that a reusable
launcher would have a far better safety record than an ELV,
the low operating cost advantage is not as obvious to me as it
apparently is to you. Past experience suggests that some 1970s
level technologies (engines, TPS) were not capable of aircraft
like operations. I can't say whether recent technological
advances (I'm now talking SSTO) have bridged the gap, but I note that
much of it comes fresh from the laboratories. Both the Venturestar
and Roton rely on many untried technologies. Assuming either or
both vehicles make it to orbit, I don't the odds are very good
that their systems will have extremely long lifetimes, require
very little expensive maintenance and inspection etc.. Was the
Comet a great hit in this respect, or the Concorde? DC-X was way
too unambitious to reveal much about SSTO.
---
As for low RLV development cost, I suspect that the "experience
base" is not large enough to allow anybody to develop an orbit
capable RLV as cheaply as easily as Burt Rutan & Jim Bede
do their homebuilt aircraft (=a DDT&E cost reduction by a factor
of 10-100 from Big Aerospace cost estimates). I note that
Gary Hudson and Len Cormier _have_ proposed such vehicles,
however, and it will be interesting to see what the actual cost
will turn out to be. Their task certainly appears to be much
harder than anything faced by messrs. Bede and Rutan -- who
draw on decades of aircraft experience even for their more
advanced designs.
---
Maybe geniuses like Pat will make it seem easy, though. Until
he does, I will regard some of his statements as little
more than smart-ass comments ("it's just an engineering problem"
etc.).
pat
mlin...@my-dejanews.com wrote:
> In article <35F54E7A...@clark.net>,
> pat <p...@clark.net> wrote:
>
> > >
> > > Non- Recurring Cost
> > > recurring cost
> > > Atlas 108.6 + 148.3 = 256.9M
> > > X-15 56.9 + 7.4 = 104.3M
> > >
> >
> > Was this a typo above? did you drop a 40? off the recurring ops cost?given
> > the totals feel right, i'll note the X-15 was half the price of the Atlas.
>
> Yup, it should read "47.4".
>
> > > Despite these reservations, I believe the basic premise is
> > > correct: it is possible to develop launchers that operate
> > > more or less like aircraft without increasing the cost and
> > > complexity too much. If the performance is reduced sufficiently
> > > (DC-X is the prime example), the vehicle can be developed
> > > and operated for costs that appear reasonable by aircraft
> > > standards. For the time being, I am drawing the line
> > > somewhere around Mach 8- or so.
> > >
> >
> > gee marcus, now we just need to be 3 times smarter then you.You used to say
> > we couldn't do anything better then mach 2+
> > so we needed to be 12 times smarter then you.
> >
> >
>
> ---
> My argument has never been that we could not do anything better
> than Mach 2, technologically speaking. We've already had the
> X-15 going to Mach 6, and the Shuttle/Buran to Mach 25. While
>
but not at what is to you an acceptable ops cost.The X-15 and SR-71 ops costs are
too high, but neither were designed around
low cost methodologies. The argument i've made is that The Ops cost budgets
could get pushed down, with a little effort.
> it indeed has been obvious to me for a long time that a reusable
> launcher would have a far better safety record than an ELV,
> the low operating cost advantage is not as obvious to me as it
> apparently is to you.
What seems close from where I stand may seem far to you.
> Past experience suggests that some 1970s
> level technologies (engines, TPS) were not capable of aircraft
> like operations.
Well, consider what money was spent where.
The X-15 had less then Half the DDTE costs of the Atlas, in your example.
extra money spent, could have easily gone to reliability and ops improvements.
> I can't say whether recent technological
> advances (I'm now talking SSTO) have bridged the gap, but I note that
> much of it comes fresh from the laboratories. Both the Venturestar
> and Roton rely on many untried technologies. Assuming either or
> both vehicles make it to orbit, I don't the odds are very good
> that their systems will have extremely long lifetimes, require
> very little expensive maintenance and inspection etc.. Was the
> Comet a great hit in this respect, or the Concorde? DC-X was way
>
the comet wasn't bad on maintenance, it needed some bugs worked out,due to the
introduction of new technologies, but consider in a time period,
the comet and B707 came out. the Comet didn't succeed, but the 707
was a hit.
> too unambitious to reveal much about SSTO.
DC-X was, but it pointed out there was lots of room in the Ops space for
improvement.
> ---
> As for low RLV development cost, I suspect that the "experience
> base" is not large enough to allow anybody to develop an orbit
> capable RLV as cheaply as easily as Burt Rutan & Jim Bede
> do their homebuilt aircraft (=a DDT&E cost reduction by a factor
> of 10-100 from Big Aerospace cost estimates). I note that
>
True, but look at the X-15/Atlas comparison. There you had a factor of 2
differencein costs, It's better nowadays with computer design tools.
> Gary Hudson and Len Cormier _have_ proposed such vehicles,
> however, and it will be interesting to see what the actual cost
> will turn out to be. Their task certainly appears to be much
> harder than anything faced by messrs. Bede and Rutan -- who
> draw on decades of aircraft experience even for their more
> advanced designs.
> ---
Rutan is the chief subcontractor to Hudson.
> Maybe geniuses like Pat will make it seem easy, though. Until
> he does, I will regard some of his statements as little
> more than smart-ass comments ("it's just an engineering problem"
> etc.).
>
The engineering is quantifiable, it's the cost and business plan that's hard.
pat
James A Davis
> The X-15 had less then Half the DDTE costs of the Atlas, in your example.
> extra money spent, could have easily gone to reliability and ops improvements.
> True, but look at the X-15/Atlas comparison. There you had a factor of 2
> differencein costs, It's better nowadays with computer design tools.
The huge difference in capability between the Atlas and the X-15 is
being overlooked in this thread.
Whatever their development and operational costs it simply can't be
overlooked that the Atlas was by far the more useful of the two
vehicles. The Atlas' contribution to national security, commerce, and
scientific and engineering knowledge completely dwarf that of the X-15.
Had the X-15 been cancelled in 1960 very little subsequent aerospace
history would have changed. The cancellation of the Atlas in 1960 would
have had a huge impact. The X-15's service history spanned about 10
years. The Atlas is still going after 40 years.
It is worth pointing out that Dore's paper was published in 1969 when
NASA was starting its push for Shuttle funding. Presumably he is still
around to do a sequel comparing the relative operational and development
costs of the Shuttle and Ariane.
Jim Davis
Jens Lerch
>Whatever their development and operational costs it simply can't be
>overlooked that the Atlas was by far the more useful of the two
>vehicles. The Atlas' contribution to national security, commerce, and
>scientific and engineering knowledge completely dwarf that of the X-15.
>Had the X-15 been cancelled in 1960 very little subsequent aerospace
>history would have changed. The cancellation of the Atlas in 1960 would
>have had a huge impact. The X-15's service history spanned about 10
>years. The Atlas is still going after 40 years.
But additional hundreds of millions of Dollar had to be spent to turn
the Atlas ICBM of 1960 into todays satellite launch vehicle.
The same amount of money may have converted the X-15 into a
mini-shuttle, launched from the back of an XB-70, able to carry about
1000kg into LEO for a few million Dollars per flight.
Jens Lerch
jle...@geocities.com
Please visit my Astronautics Page at
http://www.geocities.com/CapeCanaveral/2221
_________________________________________________
Statistics about annual launch rates by country.
Information about future Russian launchers.
mlin...@my-dejanews.com
jimd...@primary.net wrote:
> pat wrote:
>
> > The X-15 had less then Half the DDTE costs of the Atlas, in your example.
> > extra money spent, could have easily gone to reliability and ops
improvements.
>
> > True, but look at the X-15/Atlas comparison. There you had a factor of 2
> > differencein costs, It's better nowadays with computer design tools.
>
> The huge difference in capability between the Atlas and the X-15 is
> being overlooked in this thread.
Yup! I am not entirely happy with the choice of subjects, either.
X-15 vs Shrike (=air launched short/medium range missile) might
have been more relevant.
> Whatever their development and operational costs it simply can't be
> overlooked that the Atlas was by far the more useful of the two
> vehicles. The Atlas' contribution to national security, commerce, and
> scientific and engineering knowledge completely dwarf that of the X-15.
> Had the X-15 been cancelled in 1960 very little subsequent aerospace
> history would have changed. The cancellation of the Atlas in 1960 would
> have had a huge impact. The X-15's service history spanned about 10
> years. The Atlas is still going after 40 years.
I have to agree with Jens Lerch here: the X-15 could have been potentially
very useful. Commercial sounding rocket flights using a more cost
effective model. Launch from an XB-70 plus a switch to fluorine from
liquid oxygen would have pushed to maximum velocity to Mach 15 or
so, if we wanted to do some flight test experiments in the high
hypersonic region.
> It is worth pointing out that Dore's paper was published in 1969 when
> NASA was starting its push for Shuttle funding. Presumably he is still
> around to do a sequel comparing the relative operational and development
> costs of the Shuttle and Ariane.
But the Shuttle and Ariane don't have much in common, if you look at
vehicle size, capabilities technology level etc.. As (commercial-)
SPACE POLICY DECISIONS, they are comparable, yes. I suspect Dore
would complain bitterly about how his advice was ignored, in the
end.
> Jim Davis
James A Davis
> But additional hundreds of millions of Dollar had to be spent to turn
> the Atlas ICBM of 1960 into todays satellite launch vehicle.
The subsequent career of the Atlas shows this to be money well spent.
> The same amount of money may have converted the X-15 into a
> mini-shuttle, launched from the back of an XB-70, able to carry about
> 1000kg into LEO for a few million Dollars per flight.
No way. Even in its X-15A-2 version (the one with external expendable
tanks) the X-15 could not get anywhere close to orbital velocity even if
its XB-70 carrier could still achieve M=3 with this 60,000 lb monkey on
its back.
Jim Davis
James A Davis
> > Whatever their development and operational costs it simply can't be
> > overlooked that the Atlas was by far the more useful of the two
> > vehicles. The Atlas' contribution to national security, commerce, and
> > scientific and engineering knowledge completely dwarf that of the X-15.
> > Had the X-15 been cancelled in 1960 very little subsequent aerospace
> > history would have changed. The cancellation of the Atlas in 1960 would
> > have had a huge impact. The X-15's service history spanned about 10
> > years. The Atlas is still going after 40 years.
>
> I have to agree with Jens Lerch here: the X-15 could have been potentially
> very useful. Commercial sounding rocket flights using a more cost
> effective model. Launch from an XB-70 plus a switch to fluorine from
> liquid oxygen would have pushed to maximum velocity to Mach 15 or
> so, if we wanted to do some flight test experiments in the high
> hypersonic region.
A few points:
1. Sounding rockets require high altitude which the existing X-15 could
achieve, not high speed. If the existing NB-52/X-15 combination couldn't
be justified as a cheap reusable sounding rocket what chance did an
XB-70/flourine X-15 have?
2. The concurrent ASSET and PRIME programs (launched on Thor and Atlas)
were providing data in the high hypersonic flight region. What point was
there in duplicating this effort?
3. The various X-planes have taught us one thing above all else. It is
very hard to justify an aerospace vehicle that normally operates in the
velocity range from high subsonic speeds to orbital velocity. Successful
vehicles of this description can be counted on one hand (A-12/SR-71 and
Concorde).
The X-15 was conceived at a time (the mid-1950s) when it seemed that
aircraft (at first military and then civil) would go ever faster and
faster and hard data was needed for these flight regimes. Although the
X-15 was completely successful, this turned out not to be the case.
> > It is worth pointing out that Dore's paper was published in 1969 when
> > NASA was starting its push for Shuttle funding. Presumably he is still
> > around to do a sequel comparing the relative operational and development
> > costs of the Shuttle and Ariane.
>
> But the Shuttle and Ariane don't have much in common, if you look at
> vehicle size, capabilities technology level etc.. As (commercial-)
> SPACE POLICY DECISIONS, they are comparable, yes. I suspect Dore
> would complain bitterly about how his advice was ignored, in the
> end.
I would submit that Shuttle and Ariane have about as much in common as
the Atlas and the X-15, i.e. they were contemporaries. But perhaps a
Shuttle/Saturn V comparison is more appropriate. Whatever Dore (or
anyone else) might compare with the Shuttle, the conclusions drawn will
be different from the Atlas/X-15 comparison. In 1969 the X-15 was the
closest thing to an RLV. Today it is the Shuttle. Let us hope that 10
years from now we have a better selection to choose from.
Jim Davis
Scott Lowther
the NASA websites had computer generated images of the three
competitors (Rockwell, McD, LockMart). The images had the front, side
and top views with an isometric. I haven't seen these images in a
little short of forever.
Does anybody know if they might still be available somewhere?
Thanks.
pat
mlin...@my-dejanews.com wrote:
> In article <35F59A...@primary.net>,
> jimd...@primary.net wrote:
> > pat wrote:
> >
> > > The X-15 had less then Half the DDTE costs of the Atlas, in your example.
> > > extra money spent, could have easily gone to reliability and ops
> improvements.
> >
> > > True, but look at the X-15/Atlas comparison. There you had a factor of 2
> > > differencein costs, It's better nowadays with computer design tools.
> >
> > The huge difference in capability between the Atlas and the X-15 is
> > being overlooked in this thread.
>
> Yup! I am not entirely happy with the choice of subjects, either.
> X-15 vs Shrike (=air launched short/medium range missile) might
> have been more relevant.
or BOMARC. Actually Navajo, might make a good comparison.
>
>
>
> I have to agree with Jens Lerch here: the X-15 could have been potentially
> very useful. Commercial sounding rocket flights using a more cost
> effective model. Launch from an XB-70 plus a switch to fluorine from
> liquid oxygen would have pushed to maximum velocity to Mach 15 or
> so, if we wanted to do some flight test experiments in the high
> hypersonic region.
The X-15 I think did mosteverything you could expect, but there was aX-15B being
proposed which would have gone up faster and higher.
l...@tour2space.com
jle...@geocities.com (Jens Lerch) wrote:
> James A Davis <jimd...@primary.net> wrote:
>
> >Whatever their development and operational costs it simply can't be
> >overlooked that the Atlas was by far the more useful of the two
> >vehicles. The Atlas' contribution to national security, commerce, and
> >scientific and engineering knowledge completely dwarf that of the X-15.
> >Had the X-15 been cancelled in 1960 very little subsequent aerospace
> >history would have changed. The cancellation of the Atlas in 1960 would
> >have had a huge impact. The X-15's service history spanned about 10
> >years. The Atlas is still going after 40 years.
>
> the Atlas ICBM of 1960 into todays satellite launch vehicle.
> mini-shuttle, launched from the back of an XB-70, able to carry about
> 1000kg into LEO for a few million Dollars per flight.
>
> jle...@geocities.com
> Please visit my Astronautics Page at
> http://www.geocities.com/CapeCanaveral/2221
> _________________________________________________
> Statistics about annual launch rates by country.
> Information about future Russian launchers.
>
a remarkably high L/D and low SFC at mach 3. But
transonic acceleration was purposely marginal --
being designed for long range. Accordingly, I
doubt that a lump the size of the X-15 would make it
through the drag rise without adding a rocket system.
When I was project engineer for space transportation
systems at the LA Div of North American, we actually
considered supersonic towing to keep in tune with
the area rule.
I believe that the X-15/orbital idea (a little before
my time) called for a Titan launch vehicle -- much
like Dyansoar.
Best regards,
Len (Cormier) for MMI
l...@tour2space.com ( http://www.tour2space.com )
-----== Posted via Deja News, The Leader in Internet Discussion ==-----
mlin...@my-dejanews.com
jimd...@primary.net wrote:
> MARCU$ wrote:
>
> > > Whatever their development and operational costs it simply can't be
> > > overlooked that the Atlas was by far the more useful of the two
> > > vehicles. The Atlas' contribution to national security, commerce, and
> > > scientific and engineering knowledge completely dwarf that of the X-15.
> > > Had the X-15 been cancelled in 1960 very little subsequent aerospace
> > > history would have changed. The cancellation of the Atlas in 1960 would
> > > have had a huge impact. The X-15's service history spanned about 10
> > > years. The Atlas is still going after 40 years.
> >
> > very useful. Commercial sounding rocket flights using a more cost
> > effective model. Launch from an XB-70 plus a switch to fluorine from
> > liquid oxygen would have pushed to maximum velocity to Mach 15 or
> > so, if we wanted to do some flight test experiments in the high
> > hypersonic region.
>
>
> 1. Sounding rockets require high altitude which the existing X-15 could
> achieve, not high speed. If the existing NB-52/X-15 combination couldn't
> be justified as a cheap reusable sounding rocket what chance did an
> XB-70/flourine X-15 have?
Actually, what I had in mind was two different projects. An "economy"
version of the basic X-15 (i.e. capable of Mach 6) but using an improved
LOX/kerosene or LOX/methane engine optimized for economy rather than
performance. The X-15's XLR-99(?) used ammonia, which actually is a
a very low-performance fuel when burned with LOX. Kerosene is more
dense, and you get the same Isp. This version would be used as a
manned sounding rocket, and possibly as an air-launched 1st stage
for launching small satellites.
---
An ammonia/fluorine (or hydrazine/fluorine) X-15 would be optimized
for high performance and nothing else. For small vehicles, you won't
find any propellant combination that offers better performance.
Not sure if you could have reusable fluorine tanks, though.
> 3. The various X-planes have taught us one thing above all else. It is
> very hard to justify an aerospace vehicle that normally operates in the
> velocity range from high subsonic speeds to orbital velocity. Successful
> vehicles of this description can be counted on one hand (A-12/SR-71 and
> Concorde).
Well, I agree with your basic point. The only country that tried to
develop a reusable hypersonic spaceplane as its primary launch system
got badly burned, and Europe (which settled for a much more conservative,
low-tech expendable rocket) took over the commercial launch market.
> The X-15 was conceived at a time (the mid-1950s) when it seemed that
> aircraft (at first military and then civil) would go ever faster and
> faster and hard data was needed for these flight regimes. Although the
> X-15 was completely successful, this turned out not to be the case.
Military doctrine certainly played a major part. David Ashford & Patrick
Collins have said there were two options leading to orbital spaceflight
in the 1950s & 1960s. One was the ICBM route, and the other was based
on air-launched reusable rocketplanes plus highly supersonic aircraft.
The USAF investigated the Navaho, X-1 to X-5, the X-15, X-20, XB-70...
But in the end, unmanned expendable rockets appeared to provide a less
risky, more efficient and cheaper way of launching nuclear warheads.
The same hardware could be adapted to launch the first satellites and
spacecraft too, at less cost than if an advanced reusable launch system
had to be developed.
> Jim Davis
Jens Lerch
>> But additional hundreds of millions of Dollar had to be spent to turn
>> the Atlas ICBM of 1960 into todays satellite launch vehicle.
>The subsequent career of the Atlas shows this to be money well spent.
I don't have enough information about the cost of developing and
launching all the versions of the Atlas to comment on this.
>> The same amount of money may have converted the X-15 into a
>> mini-shuttle, launched from the back of an XB-70, able to carry about
>> 1000kg into LEO for a few million Dollars per flight.
>No way. Even in its X-15A-2 version (the one with external expendable
>tanks) the X-15 could not get anywhere close to orbital velocity even if
>its XB-70 carrier could still achieve M=3 with this 60,000 lb monkey on
>its back.
I was thinking of X-15D-4 and XB-70 Mark 3.
Jens Lerch
> jle...@geocities.com (Jens Lerch) wrote:
>> But additional hundreds of millions of Dollar had to be spent to turn
>> the Atlas ICBM of 1960 into todays satellite launch vehicle.
>> The same amount of money may have converted the X-15 into a
>> mini-shuttle, launched from the back of an XB-70, able to carry about
>> 1000kg into LEO for a few million Dollars per flight.
>Jens, the B-70 was designed for long-range cruise with
>a remarkably high L/D and low SFC at mach 3. But
>transonic acceleration was purposely marginal --
>being designed for long range. Accordingly, I
>doubt that a lump the size of the X-15 would make it
>through the drag rise without adding a rocket system.
>When I was project engineer for space transportation
>systems at the LA Div of North American, we actually
>considered supersonic towing to keep in tune with
>the area rule.
Sure, but hundred of millions of Dollar, or even a few billions, may
pay for a lot of modifications and improvements on the B-70, like
attaching two H-1 engines to accellerate the plane including a 75t
upper stage to at least Mach 3.
An upgraded X-15 equipped with a high-performance Lox/RP-1 engine and
using an expendable 50t drop tank, could launch over 1000kg to LEO.
>I believe that the X-15/orbital idea (a little before
>my time) called for a Titan launch vehicle -- much
>like Dyansoar.
Yes, but this would have required an expensive ELV which was capable
of launching a payload into orbit, without an X-15 as upper-stage.
James A Davis
> >No way. Even in its X-15A-2 version (the one with external expendable
> >tanks) the X-15 could not get anywhere close to orbital velocity even if
> >its XB-70 carrier could still achieve M=3 with this 60,000 lb monkey on
> >its back.
>
> I was thinking of X-15D-4 and XB-70 Mark 3.
I'm not familiar with these projects, at least not by these names. Do
you have any references?
In any event the X-15 and XB-70 would be a poor starting point for any
small reusable system. Most proposals I have seen over the years
involving air launch usually stage subsonically to minimize development
cost. An example would be
Cormier, Len; AIAA 79-0879; Utility of High Bypass Turbofans for a
Two-Stage Space Transport
And of course since then we've had interim HOTOL and Pegasus. The German
SANGER ran aground partly because of hypersonic separation issues. In
the US the difficulties with the M-12/D-21 separation at M=3 were still
fresh in mind in the late '60s.
If the US had decided to build an air launched spaceplane in the late
'60s I think it much more likely the carrier would have been the C-5,
not the XB-70, and the orbiter would have owed more to ASSET and PRIME
(X-23) than the X-15. Just my opinion.
Jim Davis
l...@tour2space.com
....snip....
>
> In any event the X-15 and XB-70 would be a poor starting point for any
> small reusable system. Most proposals I have seen over the years
> involving air launch usually stage subsonically to minimize development
> cost. An example would be
>
> Cormier, Len; AIAA 79-0879; Utility of High Bypass Turbofans for a
> Two-Stage Space Transport
I'll still stand by the arguments that subsonic staging
at altitude is a natural place to stage. However, in more
recent years, I have come to the conclusion that a
relatively simple rocket-powered reusable booster that
stages at perhaps mach 3 at low dynamic pressure appears
to make a small TSTO (with perhaps an 11 tonne orbiter)
easier to do than a significantly larger (and more
expensive) orbiter that is staged from a subsonic carrier
(e.g. a 250 tonne orbiter [with a proportionately larger
payload] launched from the back of an Antonov AN-225
in a ballistic arc).
>
> And of course since then we've had interim HOTOL and Pegasus. The German
> SANGER ran aground partly because of hypersonic separation issues. In
> the US the difficulties with the M-12/D-21 separation at M=3 were still
> fresh in mind in the late '60s.
>
> If the US had decided to build an air launched spaceplane in the late
> '60s I think it much more likely the carrier would have been the C-5,
> not the XB-70, and the orbiter would have owed more to ASSET and PRIME
> (X-23) than the X-15. Just my opinion.
>
> Jim Davis
>
Best regards,
Len (Cormier) for MMI
l...@tour2space.com ( http://www.tour2space.com )
-----== Posted via Deja News, The Leader in Internet Discussion ==-----
mlin...@my-dejanews.com
> > >tanks) the X-15 could not get anywhere close to orbital velocity even if
> > >its XB-70 carrier could still achieve M=3 with this 60,000 lb monkey on
> > >its back.
> >
> > I was thinking of X-15D-4 and XB-70 Mark 3.
>
> I'm not familiar with these projects, at least not by these names. Do
> you have any references?
The X-15D-4, I think, was a stretched delta wing version of the X-15
with a single centerline drop tank for additional performance. It
would have been capable of Mach 8. Not sure about the XB-70 Mark 3,
but my references claim that the original aircraft's engines were
capable of Mach 4 flight!! Cooling the airframe and systems would
have been a major problem, though, and extensive redesign of the
vehicle would have been required. Maybe this is what Jens was
referring to?
> In any event the X-15 and XB-70 would be a poor starting point for any
> small reusable system. Most proposals I have seen over the years
> involving air launch usually stage subsonically to minimize development
> cost. An example would be
>
> Cormier, Len; AIAA 79-0879; Utility of High Bypass Turbofans for a
> Two-Stage Space Transport
Note that Len has switched to high supersonic separation, though!
> And of course since then we've had interim HOTOL and Pegasus. The German
> SANGER ran aground partly because of hypersonic separation issues.
A far more serious problem was the astronomical cost of developing a
booster capable of Mach 4 cruise, an 11,000km range and top speed of
Mach 6.8 for space missions... You need very complex aerodynamics
and propulsion to have a passenger aircraft *and* space booster using
the same vehicle. It's a bit like designing a Greyhound bus capable
of cruising at 320 kilometers per hour. But I disagree with pat's
apparent conclusion that all supersonic HTHL boosters will be
expensive compared with other RLV options. For example, Len Cormier's
design is essentially a "drag race car" that takes off and quickly
accelerates to Mach 3-4. Such vehicles typically use brute force (engine
thrust) during takeoff and acceleration, to compensate for a comparatively
lousy aerodynamic efficiency. They are not really comparable to military
or commercial supersonic aircraft.
> In
> the US the difficulties with the M-12/D-21 separation at M=3 were still
> fresh in mind in the late '60s.
>
> If the US had decided to build an air launched spaceplane in the late
> '60s I think it much more likely the carrier would have been the C-5,
> not the XB-70, and the orbiter would have owed more to ASSET and PRIME
> (X-23) than the X-15. Just my opinion.
Well, I certainly like Robert Salkeld's C-5 launched proposal. A small
"X-spacefighter" consisting of three identical vehicles could have been
air launched from a Galaxy. Two units serve as boosters while the third
vehicle goes to orbit with a small payload. Missions could have included
space station logistics and military rapid-strike flights to polar orbit.
*Much* cheaper and more realistic than the supposedly "operational"
Space Shuttle, which currently does not launch any payloads and probably
never will be taken off its "experimental" status anyway.
> Jim Davis
Jens Lerch
>Jens Lerch wrote:
>> >No way. Even in its X-15A-2 version (the one with external expendable
>> >tanks) the X-15 could not get anywhere close to orbital velocity even if
>> >its XB-70 carrier could still achieve M=3 with this 60,000 lb monkey on
>> >its back.
>>
>> I was thinking of X-15D-4 and XB-70 Mark 3.
>I'm not familiar with these projects, at least not by these names. Do
>you have any references?
Neither do I :-)
I just made this designations up to show that the X-15A-2 and the
XB-70 Mark 1 were not the last possible configuration and that any
attempt to built an orbital X-15 would have modified both vehicles a
lot.
Tom Carman
>... Past experience suggests that some 1970s
>level technologies (engines, TPS) were not capable of aircraft
>like operations. I can't say whether recent technological
>advances (I'm now talking SSTO) have bridged the gap, but I note that
>much of it comes fresh from the laboratories. Both the Venturestar
>and Roton rely on many untried technologies
I expect that you are referring here to the problems that Shuttle had
with the SSME and the silica tiles. My view is that there wasn't an
inherent deficiency in engine and heat shield technologies at the
time. The problem was that they were shoe horned into a design that
put extreme demands (of weight and performance) on them.
Converting a fully reusable orbital stage concept into an Orbiter with
a drop tank cut development costs and technical risk a bit. But it
resulted in a dense Orbiter, subject to high reentry heat loads. And
its small size meant that the engines had to be very compact, as well
as very efficient and powerful. When you push the envelope that hard,
that soon, with so little development money, you get problems. And
once they were built, even that small amount of development money
pretty much dried up. *That's* why the new technologies are only now
getting out of the laboratories!
mlin...@my-dejanews.com
Tom_C...@csi.com (Tom Carman) wrote:
> On Tue, 08 Sep 1998 19:15:48 GMT, mlin...@my-dejanews.com wrote:
>
> >... Past experience suggests that some 1970s
> >level technologies (engines, TPS) were not capable of aircraft
> >like operations. I can't say whether recent technological
> >advances (I'm now talking SSTO) have bridged the gap, but I note that
> >much of it comes fresh from the laboratories. Both the Venturestar
> >and Roton rely on many untried technologies
>
> I expect that you are referring here to the problems that Shuttle had
> with the SSME and the silica tiles. My view is that there wasn't an
> inherent deficiency in engine and heat shield technologies at the
> time.
Interesting statement. I see no examples of durable low-maintenance TPS
from the 1970s, and there is not a single SSME class engine today that
can be described as being "low maintenance". So you apparently believe
there is some strong, indirect evidence that the technology was available?
> The problem was that they were shoe horned into a design that
> put extreme demands (of weight and performance) on them.
>
> Converting a fully reusable orbital stage concept into an Orbiter with
> a drop tank cut development costs and technical risk a bit. But it
> resulted in a dense Orbiter, subject to high reentry heat loads.
So what is the maximum heat load experienced by the Orbiter's underside
compared to a fully reusable TSTO? I don't have my Shuttle references
with me.
> And its small size meant that the engines had to be very compact, as well
> as very efficient and powerful. When you push the envelope that hard,
> that soon, with so little development money, you get problems.
However, 2800psi. staged combustion engines were part of the game right
from the late 1960s. Would the Pratt & Whitney 1,000kN engine really
have been that much better than the SSME? It seemed to operate at
mostly the same temperatures and pressures.
> And
> once they were built, even that small amount of development money
> pretty much dried up. *That's* why the new technologies are only now
> getting out of the laboratories!
mlin...@my-dejanews.com
pat <p...@clark.net> wrote:
> mlin...@my-dejanews.com wrote:
>
>>>> -As an example of this, Dore (using the RAND costing
>>>> method) claims that the X-15 would
>>>> have cost three times as much if if it were an airbreathing
>>>> Mach 5-6 aircraft designed to military specs. He also
>>>> argues that super/hypersonic airbreathing RLV boosters
>>>> don't seem very promising for this reason.
>>>and you wonder why len and the others are so skeptical of air-breathing.
Dore is essentially describing a Saenger type booster aircraft.
I don't think a "drag race type" short range accelerator type
HTHL booster would be that complex, compared to a VTxL booster.
Aerodynamic shortcomings are compensated for by carrying powerful
jet engines. But if a long cruise range, good fuel economy etc.
is required, I agree it will be much more expensive.
>>>> While KellySpace and Pioneer undoubtedly will use "aircraft
>>>> like" incremental testing to some extent, I don't think
>>>> they will perform 300-1000 flights before declaring their
>>>> vehicles operational...
>
>>> They only need to verify 3-5 trajectories, far easier then the
>>> 300-1000needed to verify atmospheric free flight.
Uh, to me it sounds as if the Pioneer Pathfinder then would need 300-1000
verifiable atmospheric free flight trajectories plus 3-5 reentry
profiles! By your logic, that is. At least that's how your statement
above comes across. It's essentially a jet aircraft, with a built-in
rocket motor for brief "jumps" above the atmosphere.
---
Besides, I don't think the X-15 abort site requirements would be
less of a problem for an orbit capable vehicle. You'd have abort
to the launch site, abort to a landing site on the other side of
the globe, probably abort once around (really easy even for a
base-first VTVL for an eastward launch) plus various reentry
from orbit options depending on the inclination and altitude.
Certainly, an early abort would subject the vehicle to higher
G-loads than if you are coming back from orbit etc..
> > ---
> > My argument has never been that we could not do anything better
> > than Mach 2, technologically speaking. We've already had the
> > X-15 going to Mach 6, and the Shuttle/Buran to Mach 25. While
> >
>
> but not at what is to you an acceptable ops cost.The X-15 and SR-71 ops costs
are
> too high, but neither were designed around
> low cost methodologies.
Well, $18,000/flight-hour for the SR-71. I think the problem was that they
were so busy meeting the performance and development cost requirements that
there was little room for "luxuries" such as low-cost maintenance. A bit
like Shuttle, really. It's easy to criticize NASA and Rockwell, but I am
curious about how much better *you* would have done a comparable RLV
*without* the benefit
of hindsight but operating within the same budget, politics and engineering
constraints as they did.
> The argument i've made is that The Ops cost budgets
> could get pushed down, with a little effort.
The argument that I've made is that this will be far easier for the
X-34 than X-33 or any SSTO.
> > Past experience suggests that some 1970s
> > level technologies (engines, TPS) were not capable of aircraft
> > like operations.
>
> Well, consider what money was spent where.
>
> The X-15 had less then Half the DDTE costs of the Atlas, in your example.
> extra money spent, could have easily gone to reliability and ops improvements.
You are right, but only if the goal had
been Cheap Access to the low hypersonic region.
Had the X-15 been capable of ~Mach 22 flight carrying a nuclear
warhead like Atlas did, there would have been even less money available for
reliability and ops improvements.
> > Maybe geniuses like Pat will make it seem easy, though. Until
> > he does, I will regard some of his statements as little
> > more than smart-ass comments ("it's just an engineering problem"
> > etc.).
> >
>
> The engineering is quantifiable, it's the cost and business plan that's hard.
The business part is the hard bit, I agree. But a significant part of the
problem is how to predict a realistic development and operations cost for
a totally new kind of vehicle...
The recent AW&ST report suggests Kistler will exceed their budget by hundreds
of millions.
> pat
pat
mlin...@my-dejanews.com wrote:
> In article <35F58E1C...@clark.net>,
> pat <p...@clark.net> wrote:
>
> > mlin...@my-dejanews.com wrote:
> >
>
> >Uh, to me it sounds as if the Pioneer Pathfinder then would need 300-1000
> verifiable atmospheric free flight trajectories plus 3-5 reentry
> profiles! By your logic, that is. At least that's how your statement
> above comes across. It's essentially a jet aircraft, with a built-in
> rocket motor for brief "jumps" above the atmosphere.
>
yes. you can put the vehicle into early ops, while continuing flight tests.if you
certify one payload weight and one fixed trajectory plus it's abort trajectories,
it's enough to start revenue service.
> ---
>
> Besides, I don't think the X-15 abort site requirements would be
> less of a problem for an orbit capable vehicle. You'd have abort
> to the launch site, abort to a landing site on the other side of
> the globe, probably abort once around (really easy even for a
> base-first VTVL for an eastward launch) plus various reentry
> from orbit options depending on the inclination and altitude.
> Certainly, an early abort would subject the vehicle to higher
> G-loads than if you are coming back from orbit etc..
>
sure. but remember, a lot of aborts can run with engines on, which flattens outthe
approach. it's only an all engine out abort that is the worst case.
inevitably that will occur. You can start revenue service without every
contingency closed, as long as you can demonstrate that is less then 1:10,000
> > > ---
> > > My argument has never been that we could not do anything better
> > > than Mach 2, technologically speaking. We've already had the
> > > X-15 going to Mach 6, and the Shuttle/Buran to Mach 25. While
> > >
> >
> > but not at what is to you an acceptable ops cost.The X-15 and SR-71 ops costs
> are
> > too high, but neither were designed around
> > low cost methodologies.
>
> Well, $18,000/flight-hour for the SR-71. I think the problem was that they
> were so busy meeting the performance and development cost requirements that
> there was little room for "luxuries" such as low-cost maintenance. A bit
> like Shuttle, really. It's easy to criticize NASA and Rockwell, but I am
> curious about how much better *you* would have done a comparable RLV
> *without* the benefit
> of hindsight but operating within the same budget, politics and engineering
> constraints as they did.
>
they ended up with an engine with less operability then the J-2 and marginallymore
performance. a larger squatter vehicle with 4 J-2s would have done a
better job.
> > The argument i've made is that The Ops cost budgets
> > could get pushed down, with a little effort.
>
> The argument that I've made is that this will be far easier for the
> X-34 than X-33 or any SSTO.
>
>
true, but the X-33 isn't doing a good job on ops.
> > > Past experience suggests that some 1970s
> > > level technologies (engines, TPS) were not capable of aircraft
> > > like operations.
> >
> > Well, consider what money was spent where.
> >
> > The X-15 had less then Half the DDTE costs of the Atlas, in your example.
> > extra money spent, could have easily gone to reliability and ops improvements.
>
> You are right, but only if the goal had
> been Cheap Access to the low hypersonic region.
>
but the Goal of the X-15 was Low hypersonics. had they increased the budgetslightly
they could have done cheap hypersonics, especially with a follow on
vehicle.
> Had the X-15 been capable of ~Mach 22 flight carrying a nuclear
> warhead like Atlas did, there would have been even less money available for
> reliability and ops improvements.
>
I don't believe Mach 22 was necessary to get a bomb to moscow.mach 10 would be
adequate.
> > > Maybe geniuses like Pat will make it seem easy, though. Until
> > > he does, I will regard some of his statements as little
> > > more than smart-ass comments ("it's just an engineering problem"
> > > etc.).
> > >
> >
> > The engineering is quantifiable, it's the cost and business plan that's hard.
>
> The business part is the hard bit, I agree. But a significant part of the
> problem is how to predict a realistic development and operations cost for
> a totally new kind of vehicle...
>
by limiting technology risk, and doing spiral development.the X-1 didn't have a
budget problem, neither did the X-15.
build core elements, and test them separately.
> The recent AW&ST report suggests Kistler will exceed their budget by hundreds
> of millions.
>
well, george mueller is used to big numbers not little numbers.
> > pat
Jan Vorbrueggen
> > Converting a fully reusable orbital stage concept into an Orbiter with
> > a drop tank cut development costs and technical risk a bit. But it
> > resulted in a dense Orbiter, subject to high reentry heat loads.
>
> So what is the maximum heat load experienced by the Orbiter's underside
> compared to a fully reusable TSTO?
Irrelevant. Tom's point is that the shuttle _system_ design forced a TPS
design that was at (or across) the edge of the possible at the time. A system
design such as that of the X-33/VS can live with a TPS of much lower
performance.
Jan
Tom Carman
>In article <35f99d9...@news.newsguy.com>,
> Tom_C...@csi.com (Tom Carman) wrote:
>> I expect that you are referring here to the problems that Shuttle had
>> with the SSME and the silica tiles. My view is that there wasn't an
>> inherent deficiency in engine and heat shield technologies at the
>> time.
>
>Interesting statement. I see no examples of durable low-maintenance TPS
>from the 1970s, and there is not a single SSME class engine today that
>can be described as being "low maintenance". So you apparently believe
>there is some strong, indirect evidence that the technology was available?
>
>> The problem was that they were shoe horned into a design that
>> put extreme demands (of weight and performance) on them.
>>
>> Converting a fully reusable orbital stage concept into an Orbiter with
>> a drop tank cut development costs and technical risk a bit. But it
>> resulted in a dense Orbiter, subject to high reentry heat loads.
>
>So what is the maximum heat load experienced by the Orbiter's underside
>compared to a fully reusable TSTO? I don't have my Shuttle references
>with me.
If you mean "on the shelf" then no, they were not available in the
70's. But the "metal shingle" and "metal multiwall" TPS ideas
proposed for X-33 were already around then. High pressure staged
combustion engines were started in the late 60's, but other lower
performing (more maintainable) engines were also in hand.
In my view, in the 70's there was one major customer for spacecraft:
NASA. And there was one big funded project: Shuttle. And the
politician's funding priorities dictated the design chosen. At that
point, the only things that could get funded were the things worked
with that design. This is a "road not taken" matter.
An orbital stage with integral tanks would be larger and less dense.
It could slow down at higher altitudes and spread the heating over a
larger area. Thus it could get away with lower performance but more
maintainable TPS. If the orbital stage was started at altitude (TSTO)
it could have used lower performance but more maintainable derivatives
of the J-2 or RL-10. The Shuttle, of course, needed a single high
performance engine type from sea level to vacuum.
My argument comes down to: what was funded to development on the 70's
was not the only thing that could have been. Some of the other
possible approaches would have been better (less expensive, more
maintainable) in the long run. But they would have required a Shuttle
design with a higher price in the near term.
mlin...@my-dejanews.com
Jan Vorbrueggen <j...@mailhost.neuroinformatik.ruhr-uni-bochum.de> wrote:
> mlin...@my-dejanews.com writes:
>
> > > Converting a fully reusable orbital stage concept into an Orbiter with
> > > a drop tank cut development costs and technical risk a bit. But it
> > > resulted in a dense Orbiter, subject to high reentry heat loads.
> >
> > So what is the maximum heat load experienced by the Orbiter's underside
> > compared to a fully reusable TSTO?
>
> design that was at (or across) the edge of the possible at the time. A system
> design such as that of the X-33/VS can live with a TPS of much lower
> performance.
"Much lower" performance? I've never quite managed to memorize those
temperature figures, but my impression has always been that there is no great
difference between the Shuttle and other RLVs as far as peak heating is
concerned? Or have I missed something here?
---
BTW, the Venturestar has a problem with total integrated heat load. Peak
heat loads are lower, true, but the descent takes longer than for the
Shuttle so you still end up having an insulation problem.
> Jan
Jan Vorbrueggen
> "Much lower" performance? I've never quite managed to memorize those
> temperature figures, but my impression has always been that there is no great
> difference between the Shuttle and other RLVs as far as peak heating is
> concerned? Or have I missed something here?
>
> BTW, the Venturestar has a problem with total integrated heat load. Peak
> heat loads are lower, true, but the descent takes longer than for the
> Shuttle so you still end up having an insulation problem.
Well, for a given mass of vehicle, the total heat load must be the same
regardless of specific weight or any other factor, as this is equivalent
to the potential and kinetic energy you are converting to heat on reentry.
The peak heat load must depend on specific weight - as you note, the lighter
vehicle such as Venturestar take longer to reenter, which makes a lower peak
heat load very likely. Note that the Shuttle has four, IIRC, different sets
of materials for its TPS, and it is only the two covering the areas with the
highest heat loads (the RCC on the leading edges of the wings and the tiles
on the bottom) that are a maintenance nightmare. In fact, the TPS has been
"simplified" as experience with actual compared to predicted heating was
gained, precisely for this reason. So I'd say that the problems with the
Shuttle TPS are a system design problem.
Jan
l...@tour2space.com
mlin...@my-dejanews.com wrote:
> In article <y4iuiq2...@mailhost.neuroinformatik.ruhr-uni-bochum.de>,
> Jan Vorbrueggen <j...@mailhost.neuroinformatik.ruhr-uni-bochum.de> wrote:
> > mlin...@my-dejanews.com writes:
> >
> > > > Converting a fully reusable orbital stage concept into an Orbiter with
> > > > a drop tank cut development costs and technical risk a bit. But it
> > > > resulted in a dense Orbiter, subject to high reentry heat loads.
> > >
> > > So what is the maximum heat load experienced by the Orbiter's underside
> > > compared to a fully reusable TSTO?
> >
> > Irrelevant. Tom's point is that the shuttle _system_ design forced a TPS
> > design that was at (or across) the edge of the possible at the time. A
system
> > design such as that of the X-33/VS can live with a TPS of much lower
> > performance.
>
> temperature figures, but my impression has always been that there is no great
> difference between the Shuttle and other RLVs as far as peak heating is
> concerned? Or have I missed something here?
>
that's an important aspect of our TPS patent. Peak
equilibrium temperatures determine how practical your
outer heat sheild material and insulation can be.
> ---
>
> BTW, the Venturestar has a problem with total integrated heat load. Peak
> heat loads are lower, true, but the descent takes longer than for the
> Shuttle so you still end up having an insulation problem.
>
Total integrated heat load should not be a serious problem
for a good design. 95 percent or the heat is radiated away.
What is required for the other 5 percent is an efficient
TPS and a good heat sink on the other side of the TPS to
absorb what gets through. Thermal conductivity is very
much a function of the outer temperature as well as the
type of insulation itself. Our TPS is potentially
superb from that point of view. And our beryllium/aluminum/
magnesium structure is superb for absorbing what heat does
get through -- so good that we can probably use organic
sealants. The X Van design starts with reentry and reentry
heating -- it's not an afterthought.
The best way to solve some of the problems that you
seem to be worried about, Marcus, is to avoid them.
And that's potentially a huge cost factor. Unfortunately,
it does require some money.
> > Jan
>
> MARCU$
>
Best regards,
Len (Cormier) for MMI
l...@tour2space.com ( http://www.tour2space.com )
-----== Posted via Deja News, The Leader in Internet Discussion ==-----
David Palmer
Jan Vorbrueggen <j...@mailhost.neuroinformatik.ruhr-uni-bochum.de> wrote:
> Well, for a given mass of vehicle, the total heat load must be the same
> regardless of specific weight or any other factor, as this is equivalent
> to the potential and kinetic energy you are converting to heat on reentry.
I thought most of the energy went to heating the atmosphere at the shock
front, and the main heating of the vehicle itself comes from: a) conduction
from the shock-heated air and b) radiant heating from the shock.
--
David Palmer dmpa...@clark.net
http://www.clark.net/pub/dmpalmer/
Frank Crary
>Total integrated heat load should not be a serious problem
>for a good design. 95 percent or the heat is radiated away.
More to the point, 95% is not the correct number. Specifically,
it is about 95% right, but the exact number depends on the
duration of the heating, and the balance between integrated
conducted and radiated heat flux. A slight change in the
reentry profile and the thermal protection system could mean
the difference between, say, 92% and 98% of the heat being
radiated away. I believe a low density vehicle (i.e. SSTO
versus Shuttle-like TSTO) would result in more heat being
radiated away, although the conductivity of the TPS may be
equally important. I've never done an analysis of reentry
heating, but I've done a fair amount of thermal modeling.
I'd say there are more than enough free parameters to let
you design a very efficient TPS. But if you lock down a
critical one (e.g. the sectional density of the vehicle)
then you are working with one hand tied behind your back.
The Shuttle did that, and I suspect this is one of the
reasons the Shuttle's TPS was a problem.
Frank Crary
CU Boulder
pat
David Palmer wrote:
i'd have to agree with dave, while for a given mass of vehicle the total work
functionis the same, how that work is radiated is subject to design issues.
pat
l...@tour2space.com
The number was meant to be illustrative and typical, not specific.
And even then, I'm talking only about a class of RLVs that
reenters at relatively low ambient densities -- the only
kind that I have found worth considering. Low planform loading
is one of the claims in our TPS patent. That technique may be
considered old hat now -- but designs that could achieve low
planform loading in a practical manner were not old hat when
I first started looking at them (long before Shuttlle, BTW).
George Herbert
>>[...]
>Low planform loading
>is one of the claims in our TPS patent. That technique may be
>considered old hat now -- but designs that could achieve low
>planform loading in a practical manner were not old hat when
>I first started looking at them (long before Shuttlle, BTW).
Uh, just to clarify, you're not trying to patent any low planform
loading re-entry vehicle now, are you? Just that as part of
one TPS system, I hope?
-george william herbert
Retro Aerospace
gher...@crl.com
l...@tour2space.com
gher...@crl4.crl.com (George Herbert) wrote:
> <l...@tour2space.com> wrote:
> >>[...]
> >Low planform loading
> >is one of the claims in our TPS patent. That technique may be
> >considered old hat now -- but designs that could achieve low
> >planform loading in a practical manner were not old hat when
> >I first started looking at them (long before Shuttlle, BTW).
>
> Uh, just to clarify, you're not trying to patent any low planform
> loading re-entry vehicle now, are you? Just that as part of
> one TPS system, I hope?
The claims in U.S. patent 4,919,366 involve an integrated
TPS system -- some claims of which call for low planform
loading reentry vehicles and the correspondingly reduced
peak equilibrium heating rates as being an integral part
of the total system.
Actually, my work on low planform loading reentry vehicles
goes back to 1961, when the practicality of such a concept
as applied to reusable launch vehicles was not generally
recognized.
>
> -george william herbert
> Retro Aerospace
> gher...@crl.com
>
Best regards,
Len (Cormier) for MMI
l...@tour2space.com ( http:/www.tour2space.com )