High altitude launch pad with SCRAMJet assistance
Alex Terrell
orbital flight because:
1. They are not optimised as rockets, and therefore increase the mass
of the launcher.
2. To get round this problem would require such a huge investment that
the launch cost would end up much higher than with simpler technology.
An idea to get around this:
The US military has been testing SCRAMJet missiles that they expect to
operate at Mach 6. For more info see:
http://www.onr.navy.mil/media/release_display.asp?ID=107
There have been discussions in this Group about air launched rockets
for payloads of a few tons.
So how about an air launched space plane, launched subsonically, as
described by Len Cormier at
<http://www.tour2space.com/economic/aiaapaps.htm>, but with two strap
on, reuable SCRAMJet boosters.
The SCRAMJet boosters would accelerate the space plane to Mach 6 (or
higher if feasible), and would then detach themselves. They would
return to Earth in the same way as the Shuttle SRBs (Anybody know what
speed they detach at?).
Using guestimated numbers: If we used a traditional rocket booster, it
might have four tons of Hydro Carbon, twenty tons of LOX, and two tons
of structure, equals 26 tons. The equivelant SCRAMJet booster could
have four tons of Hydro Carbon, one ton of oxidiser (for rocket
assist), and four tons of structure, equals 9 tons.
What sort of a performance gain is possible for LEO launch?
If the SCRAMJet technology can be made to work, and obtained without
the full development costs, compliments of the US military, could this
concept work?
Alex
Len
Although hydrocarbon (vs hydrogen) and staging help, the
extra drag losses caused by a requirement to gather air
tends to increase the fuel (not oxidizer) by a large amount.
More damaging--from the system point of view--is the extra
non-staged mass resulting from exposure of the orbiter
stage to a much more severe environment than might be
encountered using only rocket engines.
Scramjets were studied extensively in the mid-1960s.
All the optimism generated by the promise of higher specific
impulse evaporated under analysis of the total system--just
as it did again in the later NASP studies.
Many of us favor chemical rocket engines because they appear
to enable much improved access to space in the near term at
low cost and without any need for exotic technology. If someone
can beat that, more power to them. But it is hard to understand
the decades of resistance to a straigthforward approach using
rocket engines--and good space transport system design.
Best regards,
Len (Cormier)
PanAero, Inc. and Third Millennium Aerospace, Inc.
l...@tour2space.com ( http://www.tour2space.com )
Joseph S. Powell, III
"Alex Terrell" <alext...@yahoo.com> wrote in message
news:d81e59c9.03032...@posting.google.com...
> The general consensus of this group is that SCRAMJets are useless for
> orbital flight because:
>
> 1. They are not optimised as rockets, and therefore increase the mass
> of the launcher.
> 2. To get round this problem would require such a huge investment that
> the launch cost would end up much higher than with simpler technology.
>
> An idea to get around this:
>
> The US military has been testing SCRAMJet missiles that they expect to
> operate at Mach 6. For more info see:
> http://www.onr.navy.mil/media/release_display.asp?ID=107
>
> There have been discussions in this Group about air launched rockets
> for payloads of a few tons.
>
> So how about an air launched space plane, launched subsonically, as
> described by Len Cormier at
> <http://www.tour2space.com/economic/aiaapaps.htm>, but with two strap
> on, reuable SCRAMJet boosters.
>
> The SCRAMJet boosters would accelerate the space plane to Mach 6 (or
> higher if feasible), and would then detach themselves. They would
> return to Earth in the same way as the Shuttle SRBs (Anybody know what
> speed they detach at?).
Better yet, to avoid a lot of complications, simply have the system be a
TSTO (Two Stage To Orbit) vehicle - the launching platform would fly to a
high altitude and speed and the shuttle would detatch from the back and
thrust its way into orbit - the "mothership" could be designed to carry a
variety of sized shuttles, ranging from heavy cargo shuttles to smaller
shuttles that would mainly carry personnel to/from space stations - this
would be not unlike the Orion shuttle seen in 2001: A Space Odyssey.
Robb McLeod
wrote:
<snip>
>The SCRAMJet boosters would accelerate the space plane to Mach 6 (or
>higher if feasible), and would then detach themselves.
Therin lies the problem, seperation at hypersonic velocities. Not
fun.
--
Robb McLeod (rmc...@pacificcoast.net)
A bus station is where a bus stops. A train station is where a train stops.
On my desk I have a work station...
Martha H Adams
advantage of using available local resources rather than carrying them
up. In this case, oxygen for combustion. But, separation at
hypersonic velocities?
Why not separation at high enough altitude that airspeed is not an
issue? At most, the scramjet boosters could orbit once after
separating, and return to where they took off. ...I see a *lot* of
engineering to do here.
Cheers -- Martha Adams
TKalbfus
>fun.
>
How high will Mach 6 get you? The higher you are, the less of a problem
hypersonic velocities will prove.
Alex Terrell
> On 20 Mar 2003 00:03:12 -0800, alext...@yahoo.com (Alex Terrell)
> wrote:
> <snip>
> >The SCRAMJet boosters would accelerate the space plane to Mach 6 (or
> >higher if feasible), and would then detach themselves.
>
> Therin lies the problem, seperation at hypersonic velocities. Not
> fun.
That would depend on the flight profile. If the vehicle is heading up,
out of the atmosphere, it could coast for a little and then lose the
SCRAM boosters out of the atmosphere.
Again, anyone know the speed and altitude of the shuttle at SRB
seperation? The SCRAM boosters in this instance would be much smaller,
so seperation should be easier.
Henry Spencer
Martha H Adams <m...@TheWorld.com> wrote:
>Nine tons vs 26 tons is impressive; it points out the practical
>advantage of using available local resources rather than carrying them
>up. In this case, oxygen for combustion.
As Len noted, it's not that simple. This particular local resource is not
cheap to acquire. You end up with substantially heavier hardware, and you
also end up needing rather a lot more fuel... which hurts particularly
badly because the fuel probably has to be hydrogen, not hydrocarbons.
(Scramjets put a big premium on extremely rapid combustion, and hydrocarbon
combustion is a multi-step process that tends to be relatively slow. There
has been some speculation about hydrocarbon-fueled scramjets, but it adds
yet another difficulty to an already extremely hard design problem.)
>But, separation at hypersonic velocities?
>Why not separation at high enough altitude that airspeed is not an
>issue?
For one thing, because scramjets can't get you there. Pretty much by
definition, if there is not enough dynamic pressure to complicate
separation, there is not enough to run a scramjet intake. Now the first
stage needs a major rocket phase... (Well, in addition to the one it
probably needs to get up to scramjet speeds...)
--
"Bin Laden must be laughing his beard off." | Henry Spencer
-- Wes Oleszewski | he...@spsystems.net
Henry Spencer
Alex Terrell <alext...@yahoo.com> wrote:
>That would depend on the flight profile. If the vehicle is heading up,
>out of the atmosphere, it could coast for a little and then lose the
>SCRAM boosters out of the atmosphere.
Unfortunately, the only way it's going to be heading up is if it somehow
pulls up hard -- very difficult in thin air -- after accelerating.
Scramjets should not be thought of as rockets which magically don't need
oxidizer tanks; almost certainly they will have much lower thrust, like
ordinary jet engines (indeed, probably more so), and will need to do their
accelerating mostly horizontally. An inclined trajectory would be out of
the atmosphere before there is much chance to accelerate.
Richard Schumacher
So, spend a few billion dollars and several years in R&D to save $100,000
worth of oxygen on each flight. Tell us again why that makes sense?
Alex Terrell
> In article <b5qb4t$331$1...@pcls4.std.com>,
> Martha H Adams <m...@TheWorld.com> wrote:
> >Nine tons vs 26 tons is impressive; it points out the practical
> >advantage of using available local resources rather than carrying them
> >up. In this case, oxygen for combustion.
>
> As Len noted, it's not that simple. This particular local resource is not
> cheap to acquire. You end up with substantially heavier hardware, and you
> also end up needing rather a lot more fuel... which hurts particularly
> badly because the fuel probably has to be hydrogen, not hydrocarbons.
> (Scramjets put a big premium on extremely rapid combustion, and hydrocarbon
> combustion is a multi-step process that tends to be relatively slow. There
> has been some speculation about hydrocarbon-fueled scramjets, but it adds
> yet another difficulty to an already extremely hard design problem.)
>
"Arlington, VA -- The Office of Naval Research (ONR) and the Defense
Advanced Research Projects Agency (DARPA) successfully conducted the
first-ever ground test of a full-scale, fully integrated hypersonic
cruise missile engine using conventional liquid hydrocarbon fuel on
May 30, 2002. The test, performed in a wind tunnel at NASA Langley
Research Center, Hampton, Va., demonstrated robust operation of the
engine at simulated hypersonic cruise conditions (Mach 6.5 at 90,000
feet altitude)."
If LH2 allows the SCRAM speed to increase, it may be worth
considering. However, that would not attract ONR funds.
> >But, separation at hypersonic velocities?
> >Why not separation at high enough altitude that airspeed is not an
> >issue?
>
> For one thing, because scramjets can't get you there. Pretty much by
> definition, if there is not enough dynamic pressure to complicate
> separation, there is not enough to run a scramjet intake. Now the first
> stage needs a major rocket phase... (Well, in addition to the one it
> probably needs to get up to scramjet speeds...)
That depends on the angle of attack. If at SCRAMJet cut off you have a
few degrees of climb, you could trade some speed for a lot of height -
Say enough to get you from 90,000 feet to 120,000 feet, which would
slow the thing down from Mach 6.5 to Mach 6.35. At worst, start the
rockets, go to Mach 9 at 180,000 feet, and then detach.
As regards the initial boost, I'm proposing the SCRAMJets as side
mounted boosters. The Main Engine on the Rocket Plane could provide
the initial boost, throttle down to minimum power during the SCRAM
phase (about 60 secs at 2.5g), and then throttle up again.
Alternatively, SCRAMJets can be designed to fire oxidiser into them to
make a rocket. Not an optimised rocket, but good enough for Mach 0.8
to Mach 1.5.
Overall, I think the idea could be a flyer if a Mach 6.5 SCRAMJet
missile goes into production. Then it becomes proven technology.
Henry Spencer
>> yet another difficulty to an already extremely hard design problem.)
>>
>That's what I thought, but to quote from the source:
>cruise missile engine using conventional liquid hydrocarbon fuel on
>engine at simulated hypersonic cruise conditions (Mach 6.5 at 90,000
>feet altitude)."
Note that the word "scramjet" does not appear. This is probably an
ordinary ramjet. That is close to the upper limit for them, but not
beyond the bounds of plausibility.
Alex Terrell
> In article <d81e59c9.03032...@posting.google.com>,
> Alex Terrell <alext...@yahoo.com> wrote:
> >> has been some speculation about hydrocarbon-fueled scramjets, but it adds
> >> yet another difficulty to an already extremely hard design problem.)
> >>
> >That's what I thought, but to quote from the source:
> >"...first-ever ground test of a full-scale, fully integrated hypersonic
> >cruise missile engine using conventional liquid hydrocarbon fuel on
> >May 30, 2002... robust operation of the
> >engine at simulated hypersonic cruise conditions (Mach 6.5 at 90,000
> >feet altitude)."
>
> Note that the word "scramjet" does not appear. This is probably an
> ordinary ramjet. That is close to the upper limit for them, but not
> beyond the bounds of plausibility.
Sorry, if you check the full text, you'll see it's a SCRAMJet. I
thought Mach 4-5 or so would be the limit of a RAM.
Regarding the other argument, I did some simple calculations. Assume
relaease is at 10,000m at 200m/s, and SCRAM cut out is at 30,000m at
2,200m/s (a bit faster than the Navy goal, but well within predicted
SCRAMJet capabilities). Acceleration along the flight path is 24m/s/s.
At SCRAMJet cutout, the vehicle coasts. It's climb will take it to
42,000m and a speed of 2156 m/s relative to Earth surface. Then the
SCRAMJets detach, to reenter with parachute assists, to be recovered
400km down range. The rocket engine starts up to take the vehicle from
2,156m/s to 8,000m/s.
Your thoughts??
Henry Spencer
Alex Terrell <alext...@yahoo.com> wrote:
>Sorry, if you check the full text, you'll see it's a SCRAMJet.
As Ed Ruf has noted, it's actually kind of a weird hybrid. An interesting
approach; it would be nice to see a flight test.
>I thought Mach 4-5 or so would be the limit of a RAM.
No, ramjets start to suffer from the incoming air getting awfully hot at
around that point, but they are possible -- with diminishing performance
and increasing engineering problems -- somewhat beyond that.
>Regarding the other argument, I did some simple calculations. Assume
>relaease is at 10,000m at 200m/s, and SCRAM cut out is at 30,000m at
>2,200m/s ...
Bear in mind that something else will have to fill the gap between 200m/s
and scramjet start speed, which is likely to be at least 500m/s and
possibly rather higher.
Also note that a uniform acceleration along a flight path at a uniform
slope between those two endpoints almost certainly will result in the
complete destruction of the vehicle by overheating. Because the later
part of the path is covered much more quickly than the earlier part, most
of the acceleration must happen early in the path. For example, at a
uniform acceleration, half the velocity is acquired in the first quarter
of the distance. That means you're approaching Mach 4 at only about
45,000ft, which equals rapid destruction of vehicle; not even the X-15
could survive that. It will be necessary to do what the X-15 did for its
"speed" flights: begin with a steep climb, then level off and accelerate
more or less horizontally.
>...Acceleration along the flight path is 24m/s/s.
*Hold it right there.* I don't believe there has ever been an airbreathing
vehicle of any kind which has achieved 2.4G forward acceleration, let
alone done so at highly supersonic speed. This goes beyond implausible;
this is ludicrous. A tenth of that would be more plausible, and that
demands a much less steeply inclined flight path.
This is why I cautioned you against treating scramjets as if they were
rockets without oxidizer tanks. They are a different and (for missions
involving rapid acceleration) much inferior type of propulsion system.
When the military builds ramjet-propelled missiles, they usually use
rocket boost to take the missile to cruising speed, with the ramjet
supplying cruise thrust only.
>At SCRAMJet cutout, the vehicle coasts. It's climb will take it to
>42,000m and a speed of 2156 m/s relative to Earth surface. Then the
>SCRAMJets detach, to reenter with parachute assists, to be recovered
>400km down range. The rocket engine starts up to take the vehicle from
>2,156m/s to 8,000m/s.
>Your thoughts??
My main thought is that you will get better performance at much lower
development cost if you forget the scramjets and use rockets throughout.
There have been a number of launcher design studies which started out with
mixed jet/rocket systems, did a quick comparison with an all-rocket system
just for the sake of technical due diligence... and ended up tearing up
the original design concept and going with the all-rocket design, because
it was better and cheaper in every way. More payload, simpler hardware,
less heating, less dry mass, lower fuel costs, better-understood technology,
lower operating budget, *much* lower development budget.
"Air breathing is a privilege that should be reserved for the crew."
-- Mitch Burnside Clapp
Alex Terrell
Unfortunately, you're probably right (as usual). Some fighters can do
about 1.5g forward acceleration, but they don't mass 100 tons
Have the SCRAMJet studies you refer to looked at SCRAMJet side
boosters (i.e. an adapted missile)? The only ones I've seen are
SCRAMJet SSTO, and Saenger type TSTO concepts, with dual vehicles.
It seems a much simpler approach than any other SCRAMJet concept.
Using SCRAMJets at the same time as main rocket engine could make the
seperation issue much easier to solve.
I might come back on this one if the some military start producing
SCRAMJet missiles on a large scale. I know a lot of people say why not
just make the launch vehicle bigger, but I think there's a lot of
merit in keeping mass down to enable air launch (without buying the An
225).
he...@spsystems.net (Henry Spencer) wrote in message news:<HCJF0...@spsystems.net>...
Azt28
>
>Bear in mind that something else will have to fill the gap between 200m/s
>and scramjet start speed, which is likely to be at least 500m/s and
>possibly rather higher.
>
What about the SKYLON concept? It can can start from v=0 and use cooling air
system at high speed.
Yvan Bozzonetti.
Henry Spencer
Azt28 <az...@aol.com> wrote:
>>Bear in mind that something else will have to fill the gap between 200m/s
>>and scramjet start speed, which is likely to be at least 500m/s and
>>possibly rather higher.
>
>What about the SKYLON concept? It can can start from v=0 and use cooling air
>system at high speed.
If you must airbreathe, Alan Bond (originator of HOTOL and Skylon) had the
right idea: "Any hybrid engine must end up being a very efficient rocket
for most of the flight. I began with a good rocket engine and made it a
bad air-breather. Everybody previously had done the reverse."
I still favor pure-rocket solutions myself, but Bond's concepts (which
start out airbreathing and switch to rocket around Mach 6) make a whole
lot more sense than scramjets.
Henry Spencer
Alex Terrell <alext...@yahoo.com> wrote:
>Unfortunately, you're probably right (as usual). Some fighters can do
>about 1.5g forward acceleration, but they don't mass 100 tons
I think you'll also find that they can do that only fairly briefly in
thick near-sea-level air. (It has to be brief because drag builds up fast
as speed rises.) They can't do it at Mach 2 at 40kft.
>Have the SCRAMJet studies you refer to looked at SCRAMJet side
>boosters (i.e. an adapted missile)? The only ones I've seen are
>SCRAMJet SSTO, and Saenger type TSTO concepts, with dual vehicles.
The studies I refer to mostly weren't considering scramjets. These were
for real vehicles which wanted to use real propulsion systems, not
research projects.
Scramjets don't just strap on, alas. In general, the whole vehicle has to
be built around the scramjet if it is to work efficiently. The vehicle
body forward of the scramjet is an important part of the scramjet intake,
and the aft body can figure into the exhaust behavior too. Oh, you might
be able to compromise on efficiency if the scramjets don't play a big role
in the total ascent... but then you have to ask why you're bothering with
scramjets at all.
Alex Terrell
> So, spend a few billion dollars and several years in R&D to save $100,000
> worth of oxygen on each flight. Tell us again why that makes sense?
The concept only works if the Navy spends the few billion.
Then it could make sense because you increase your payload mass from
about 5 tons to 10 tons, with virtually the same system, and using the
same launch platform, and with the same operating costs.
Richard Schumacher
Alex Terrell wrote:
> > So, spend a few billion dollars and several years in R&D to save $100,000
> > worth of oxygen on each flight. Tell us again why that makes sense?
>
> The concept only works if the Navy spends the few billion.
>
> Then it could make sense because you increase your payload mass from
> about 5 tons to 10 tons, with virtually the same system, and using the
> same launch platform, and with the same operating costs.
Same system as what? As Mr. Spencer points out you can't just strap a scramjet onto an existing
vehicle. Much simpler and cheaper to build a bigger rocket.