Why does VX/VY change with Altitude?
LMart59448
BRgds
John T. Lowry
To the approximation of the "Bootstrap Approach" -- close linearity of
the propeller polar -- Vx does NOT, in KCAS, change with altitude. Vy does
(calibrated, again) and gets lower. There's no simple answer why because Vy
depends on several factors; their conjoined but separate altitude
dependencies make the total effect. But it might help to look at it this
way: At the absolute ceiling, only one air speed is possible. So Vx, Vy,
Vmax, Vmin have all become one and the same speed. So you can also ask "Why
does Vmax get smaller with altitude?"
John.
John T. Lowry, PhD
Flight Physics; Box 20919; Billings MT 59104
Voice: 406-248-2606
LMart59448 wrote in message
<199809021915...@ladder01.news.aol.com>...
John J. Miller
>
>way: At the absolute ceiling, only one air speed is possible. So Vx, Vy,
>Vmax, Vmin have all become one and the same speed. So you can also ask "Why
>does Vmax get smaller with altitude?"
>
Because you've run out of power?
John J. Miller
jo...@mcdata.com
John T. Lowry
Not ONLY power, though of course that figures in. So do the drag
characteristics, propeller characteristics, and of course the gross weight.
An interesting and easy experiment is to find the airplane's BANKED
absolute ceiling for given conditions. To do that, pick a relatively high
altitude, say 10,000 ft, go to full throttle, and see how much you can bank
before the airplane stops climbing at all. From that information one can
calculate absolute ceiling (which in fact you cannot get to with finite time
and fuel).
John.
John T. Lowry, PhD
Flight Physics; Box 20919; Billings MT 59104
Voice: 406-248-2606
--
John T. Lowry, PhD
Flight Physics; Box 20919; Billings MT 59104
Voice: 406-248-2606
John J. Miller wrote in message <6sk8ub$3lm$3...@news-2.csn.net>...
HLAviation
> To the approximation of the "Bootstrap Approach" -- close linearity of
>the propeller polar -- Vx does NOT, in KCAS, change with altitude. Vy does
>(calibrated, again) and gets lower. There's no simple answer why because Vy
>depends on several factors; their conjoined but separate altitude
>dependencies make the total effect. But it might help to look at it this
>Vmax, Vmin have all become one and the same speed. So you can also ask "Why
>does Vmax get smaller with altitude?"
This is a very intresting way to answer a question that was obviously asked by
a person with little knowledge of aerodynamics. I'm sure you lost him, your
choice of semantics caused me to read it 3 times to fully understand that you
truy didn't answer the question.
Robert Fiscella
With all due respect, I have never followed anything John T. Lowry has posted.
I assume he has a good knowledge of aerodynamics, but he could make more of
an effort to communicate the essentials to those of us who do not have
advanced, or even undergraduate degrees in math or physics.
Rob Fiscella, ATP
John T. Lowry
You guys/gals have brought up the very interesting question of transferring
thought over the Internet. I see two aspects, the general societal one and
the specific Internet one.
On the general societal aspect, the major problem is that we are in a real
educational slump. I'm not talking about literacy as defined by the Dept. of
Education, or numbers of high school or college graduates. I mean the real
thing. I recently read that someone said to Richard Feynman, when he was
disappointed about getting an idea into the head of a world leader,
"Richard, those guys have no more idea what you're up to than the Tuscan
peasants knew what Galileo was trying to do." In a more modern context, ask
yourself, "What proportion of the 535 U.S. federal Representatives and
Senators could correctly solve -- without calling a meeting or letting a
consulting contract -- a simple quadratic equation like 2X^2 - 5*X + 3 = 0?
I would guess maybe 5%.
The standard in a truly educated society would be much different. First of
all, having a nodding acquaintance with a subject would not be misconstrued,
as it often is currently, as understanding that subject. Actual intellectual
life has no relation to a TV talk show where glibness is king. In real work,
as soon as a single phrase or concept pops up which the listener does not
understand, he or she says so. You can't "lower your shoulder" and bull your
way to education. Can either of HL Aviation (anonymous) or Capt. Fiscella
tells us (veridically) what 'the propeller polar' actually means? If not,
nothing against them if they can't, but quite a bit against them, in
educability, that they didn't.
Now to the specific Internet problem. In a classroom setting I'm paid to
start the students off wherever they may be. If we have to go over high
school algebra, so be it. Sometimes even their arithmetic is somewhat fuzzy.
But on the Internet, we're flying blind with no attitude indicator. Lord
only knows what the education levels of the various participants are! And
brevity is required. I'm scornful of the current administration's goal of
connecting "every classroom in America to the Internet." To my mind, and by
my standards, there is very little true education going on there. The real
thing is both tougher and less expensive. It involves going over and over a
new idea, by yourself, coming at it various ways, formulating possible
examples, and asking simple questions about it, and answering them, until
you've finally got it. It is essentially a solitary business, social only in
the sense that human language is employed and that we build on the earlier
ideas of our forebears. A faster modem won't help.
Enough. The Bootstrap Approach explains essentially all of quasi-steady
state propeller-driven aircraft performance, accurately, and requires
nothing beyond "ordinary" high school mathematics (algebra and
trigonometry). But it does actually require those. Not just a nodding
acquaintance. Not just buzzwords. There IS one other thing: an enquiring
mind can't hurt.
John.
John T. Lowry, PhD
Flight Physics; Box 20919; Billings MT 59104
Voice: 406-248-2606
Robert Fiscella wrote in message <35EE350B...@home.com>...
Reg Whittall
John T. Lowry wrote:
and wrote and wrote and wrote.....
Dear John, if all the teachers in the USA share your communicative skills, I'm not surprised there
is currently a 'real educational slump' as you put it.
Regards,
Reg Whittall
John T. Lowry
me except geographic boundaries.
John.
John T. Lowry, PhD
Flight Physics; Box 20919; Billings MT 59104
Voice: 406-248-2606
Reg Whittall wrote in message <35EEA6C3...@club-internet.fr>...
Hilton Goldstein
>With all due respect, I have never followed anything John T. Lowry has
posted.
> I assume he has a good knowledge of aerodynamics, but he could make more
of
>an effort to communicate the essentials to those of us who do not have
>advanced, or even undergraduate degrees in math or physics.
There are hundreds of people on the NGs willing to share 'flaring' or
'logging' or 'high wing vs. low wing' information. It is all valued of
course. However, how many of us can share their mathematical knowledge of
flight and write it in a manner understandable by 'math savy' newsgroupers?
One I know of - John. As someone who presents unique information to these
NGs, I for one, value John's contributions. While not everyone is
particularly interested in polar this and that, some of us are.
Thanks for your contributions John.
Hilton
Stellar Semiconductor, Inc.
2355 Oakland Road, suite 1, San Jose, CA 95131
Tel: 408-955-9663 x154, Fax: 408-955-9671
http://www.stellarsemi.com
Doug S
>
> I doubt that the average teacher in the U.S. right now shares anything with
> me except geographic boundaries.
> John.
I'm surprised your ego even fits into a geographic boundary...thank god
for filters.
bye
DS
Opinions expressed herein are my own and may not represent those of my employer.
Patrick W. P. Dirks
May I ask why you post to these newsgroups? Are you just trying to start
a high-level conversation among the perhaps handful of readers with a
graduate aerodynamics education or are you trying to help the poor fellow
who asked the question get an answer?
Me, I believe I've had a least an average education (I *CAN* solve a
quadratic equation, for instance), but I have no idea what a "propeller
polar" is or how it figures into this problem. For that matter, I've
never heard of "the bootstrap approach" and references to it don't really
mean anything to me and I don't think it's reasonable to start by
excluding from the conversation anyone who isn't already familiar with
your preferred level of discourse.
If you're trying to educate the readers on this newsgroup or even just
trying to answer the questioner, how about at least providing some
reference to a description or a few words of the implications of concepts
that may be unfamiliar (such as "assuming propeller thrust goes up
linearly with RPM", or whatever)?
Thanks in advance,
-Pat Dirks.
P.S. For what it's worth, I remember Vx INCREASES with altitude and Vy
DECREASES with altitude until they both meet at the absolute altitude,
another method of actually computing the latter. I believe Kershner did a
nice job explaining the phenomena in one of his books: I'll see if I can
find his explanation.
In article <6sm52e$7tc$1...@news.mcn.net>, "John T. Lowry" <jlo...@mcn.net> wrote:
> The standard in a truly educated society would be much different. First of
> all, having a nodding acquaintance with a subject would not be misconstrued,
> as it often is currently, as understanding that subject. Actual intellectual
> life has no relation to a TV talk show where glibness is king. In real work,
> as soon as a single phrase or concept pops up which the listener does not
> understand, he or she says so. You can't "lower your shoulder" and bull your
> way to education. Can either of HL Aviation (anonymous) or Capt. Fiscella
> tells us (veridically) what 'the propeller polar' actually means? If not,
> nothing against them if they can't, but quite a bit against them, in
> educability, that they didn't.
<SNIP>
> Enough. The Bootstrap Approach explains essentially all of quasi-steady
> state propeller-driven aircraft performance, accurately, and requires
> nothing beyond "ordinary" high school mathematics (algebra and
> trigonometry). But it does actually require those. Not just a nodding
> acquaintance. Not just buzzwords. There IS one other thing: an enquiring
> mind can't hurt.
--
Patrick W. Penzias Dirks __!__ Phone: (408) 974-2057
Apple Computer, Inc. _______(*)_______ Fax: (408) 974-0362
1 Infinite Loop, MS 302-4K ! ! ! URL: www.apple.com
Cupertino, CA 95014 Email: p...@apple.com
PGP Key fingerprint = DE E8 3D 0B 34 C4 B5 90 4C C8 54 B3 64 73 3A 17
NOTE: I don't speak for Apple; my postings are my personal opnions.
Nothing I write should be mistaken for Apple's opinion as a
corporation.
John T. Lowry
Thanks for asking some honest questions. Here are my answers.
I post to rec.aviation.piloting because I enjoy reading the posts.
Occasionally questions are asked to which I feel I can contribute to the
answer. Unfortunately, the answer is sometimes much longer than the question
and then we have a problem. But your approach, asking What in the hell is a
propeller polar? (or words to that effect), and How about giving a few words
on the implications of concepts?, is the proper one. Here are answers to
those two specific questions.
The propeller polar is a graph of CT/J^2 as a function of CP/J^2 (or vice
versa) and, for operational propellers, is very close to linear. For
reasons, see von Mises' Theory of Flight ca. pp. 308 ff. For typical GA
propellers, the R^2 measure of linearity is commonly around 0.96. CT is the
thrust coefficient of the propeller, a function of advance ratio J = V/nd, V
air speed, n propeller circular speed, d propeller diameter. CP is the
propeller's power coefficient function, also depending on J. There are two
such independent functions because mechanically viable propellers move, in a
sense, in two directions.
For references to the "Bootstrap Approach" -- so called because to use it
one "flies the airplane (for about an hour) to see how the airplane flies
(under all steady circumstances)" -- I have to refer you to a couple of
articles in Journal of Aircraft and Journal of Aviation/Aerospace Education
and Research. I am the originator of that method and the author of those
articles. AIAA (American Institute of Aeronautics and Astronautics) will be
coming out with a full-length monograph on the subject, tentatively
"Performance of Light Aircraft", though it's uncertain whether that will be
under their Progress Series (research oriented) or under their General
Series (more nearly popular). Also, Flight Physics has a field guide for
actually doing the Bootstrap Approach test flights, "Computing Airplane
Performance with the Bootstrap Approach," for sale for $45. And an
accompanying disk of spreadsheet templates, to speed work, for another $45.
As far as Kershner, or any other aviation authority, is concerned, I have
nothing to say. My work has to stand on its own, supported only by good
reasoning and by experiment.
Now I have a question to ask you. It's about the disclaimer in your
"signature." What could it possibly mean for Apple to have an opinion as a
corporation?
But I don't want to detract from the main and beneficent point you made: If
one doesn't know, one should ask! Simple as it is, that's what separates out
the few good students, and ultimately knowledgeable adults, from the rest.
I fully stand by my fairly harsh words about mainstream American education.
I believe that in fifty years or so many people are going to ask: Why did
they (meaning us now) DO that to themselves? It really is hard to
understand. Especially when knowing is so much more satisfying than only
pretending to know. Now about that quadratic equation: did you find both
roots?
John.
John T. Lowry, PhD
Flight Physics; Box 20919; Billings MT 59104
Voice: 406-248-2606
Patrick W. P. Dirks wrote in message ...
>> The standard in a truly educated society would be much different. First
of
>> all, having a nodding acquaintance with a subject would not be
misconstrued,
>> as it often is currently, as understanding that subject. Actual
intellectual
>> life has no relation to a TV talk show where glibness is king. In real
work,
>> as soon as a single phrase or concept pops up which the listener does not
>> understand, he or she says so. You can't "lower your shoulder" and bull
your
>> way to education. Can either of HL Aviation (anonymous) or Capt. Fiscella
>> tells us (veridically) what 'the propeller polar' actually means? If not,
>> nothing against them if they can't, but quite a bit against them, in
>> educability, that they didn't.
>
><SNIP>
>
>> Enough. The Bootstrap Approach explains essentially all of quasi-steady
>> state propeller-driven aircraft performance, accurately, and requires
>> nothing beyond "ordinary" high school mathematics (algebra and
>> trigonometry). But it does actually require those. Not just a nodding
>> acquaintance. Not just buzzwords. There IS one other thing: an enquiring
>> mind can't hurt.
>
Paul Baechler
pat...@DONTSPAMME.worldnet.att.net wrote:
> Reg Whittall <gm...@club-internet.fr> wrote:
>
> >Dear John, if all the teachers in the USA share your communicative
skills, I'm not surprised there
> >is currently a 'real educational slump' as you put it.
>
> If you don't like the fact that John posts answers at a high
> level, post the answer yourself, or translate John's. There
> is plenty being posted that is easy to understand, and too
> little that lets us stretch our minds. I say - keep it up
> John.
>
> How many pilots know that stall speed and Vx and Vy and Vne,
> etc. all become the same at high altitude? (U2 pilots know
> it). That fact alone, and its relationship to the question
> originally asked was a valuable contribution.
Vx and Vy become the same at absolute ceiling, which is the point further
climb becomes impossible. Level flight is still possible. There is no
point within the flight envelope that Vs, Vx, Vy, and Vne become the same.
Roy Smith
> Me, I believe I've had a least an average education (I *CAN* solve a
> quadratic equation, for instance), but I have no idea what a "propeller
> polar" is or how it figures into this problem.
I appreciate the technical answers, even though I realize they're not for
everybody. My background is in engineering. I do know what a polar
diagram is, although I first saw them used to explain optimum upwind and
downwind angles in racing sailboats. I find the typical "pseudo-physics"
answers in most flying textbooks to be infuriating because I can see the
flaws in the explanations and aren't sure how much of the rest of it I
should believe.
In my teaching, I try to adjust my presentation to fit the student. I was
recently introducing a student to DME, which he had never used before. He
was an engineer by background, so when I explained that the speed the DME
displayed was the dot product of our velocity and position relative to the
VOR, he instantly knew what I meant. With somebody who doesn't have that
math background, I would get the same concept accross, but it would take a
lot more words and some drawings.
On the net, you have the option to read what interests you and pass the
other stuff by. If you find John's explanations too technical, skip them
and move on to some other posting.
LMart59448
I think I got a lot more info than I expected. I have a CFI-ASEL&MEL Rating.
I've read Skip Smith's explenation but was searching for a little more.
Once agian thank you everyone.
Brgds/Louis Martinez-Anchorage, Alaska
HLAviation
>and move on to some other posting
I like the fact that he can answer the question properly and I would love to
understand the answer. But unfortunatly I couldn't afford the doctoral degree
to understand his answer. Your observation of most texts having incorrect
information is all too true. Therefore people like me deeply appreciate those
"extra words" so we can understand the material properly also.
John T. Lowry
platform. Therefore we had lengthy "review" sessions once back down. The
same could be said of the Internet. Noise again, and time is short.
I believe HLAviation is mistaken in believing that a doctoral degree is
needed in order to understand my explanations. In the proper setting (that
is, taking the necessary time), high school mathematics suffices for almost
all of even my forthcoming "big book." That means algebra, trigonometry, and
the function concept. I'll grant that for optimization questions (what is
the optimum turnaround maneuver if your engine fails soon after takeoff, for
instance), a little beginning calculus is required. What is required more is
the ability and patience to calmly sit down and do a little plodding, one
step at a time. Waving off that pedestrian need with "I need more degrees"
is just throwing out the baby with the bath water.
It's interesting (at least to me) that in the first academic job I ever had,
teaching Freshman English at the University of Texas, one of the essays we
studied, by Jacques Barzun, was entitled "The Decline of Attention." He was
bemoaning the fact (or at least his opinion) that mainstream American
society has lost much of its ability to, in essence, sit down, shut up, and
pay attention to an idea. And that was back in the 1950s! We can only guess
what he'd have to say about the 20-second sound bite.
A respectable theory of small aircraft performance is accessible to,
"learnable by," almost any interested pilot. But the requisite five to ten
hours of attentiveness can't be waved off.
John.
John T. Lowry, PhD
Flight Physics; Box 20919; Billings MT 59104
Voice: 406-248-2606
HLAviation wrote in message
<199809040233...@ladder03.news.aol.com>...
HLAviation
Alexander Perry
altitude, weight and CoG interact to determine how the plane flies.
This is especially true for configurations you hope not to have to
experience, since the basic understanding of these interactions are
how you resolve apparently contradictory information when something
fails in flight. Aerodynamic principles are easy, but the math can
get difficult; so when the math is difficult, sketch the curve and get
a feel for the answer. [IMHO]
> > >Dear LMart and All:
> > > To the approximation of the "Bootstrap Approach" -- close linearity of
> > >the propeller polar -- Vx does NOT, in KCAS, change with altitude. Vy does
> > >(calibrated, again) and gets lower. There's no simple answer why because Vy
> > >depends on several factors; their conjoined but separate altitude
> > >dependencies make the total effect. But it might help to look at it this
> > >way: At the absolute ceiling, only one air speed is possible. So Vx, Vy,
> > >Vmax, Vmin have all become one and the same speed. So you can also ask "Why
> > >does Vmax get smaller with altitude?"
> > > John.
> > >John T. Lowry, PhD
> > >Flight Physics; Box 20919; Billings MT 59104
> > >Voice: 406-248-2606
Interesting; the Vx in KCAS does change with DA on many planes, John.
Robert Fiscella <aero...@home.com> wrote:
> With all due respect, I have never followed anything John T. Lowry has posted.
> I assume he has a good knowledge of aerodynamics, but he could make more of
> an effort to communicate the essentials to those of us who do not have
> advanced, or even undergraduate degrees in math or physics.
I think that is a bit harsh; if you have a vague idea of how things
behave, his summaries are interesting. In any case, he is trying to
drum up customers, so can hardly be blamed for being terse.
[HERE IS MY ATTEMPT]
For a given stable climb/descent/etc, the energy lost by drag and by
change in aircraft altitude has to be replaced by the engine. For a
lot of reasons, which should be discussed separately, the maximum
power available from the engine decreases rapidly with altitude (to be
specific, density altitude). To the extent that you have spare power
between the replacement value and the maximum value, you can do
something with it and choose to fly slow, fast, climb, go up at an
angle. At the ceiling of the aircraft, there is exactly no spare
power, so you have no choices and Vx,Vy,etc are all the same.
A secondary factor worth remembering is that, while indicated
airspeeds are the same at altitude and the best glide airspeed and
glide angle are approximately unchanged, your true airspeed is higher.
This means that you go down the angled slope faster. If you fly
level, it takes a bit more power to avoid going down that slope.
The curve of how Vx and Vy move together as altitude increases from
sea level is sometimes in the POH and (if it is) is worth reading
through. For most C172s, it seems to be about linear so that ...
At sea level, Vx=59 Vy=73 KIAS, 800fpm max
At 15,000ft, Vx=65 Vy=65 KIAS, 0fpm max (ceiling)
i.e. Vx=59+DA/3000, Vy=73-DA/2000, climb=800-DA/20 approximately
Note that they do not change at the same rate. Note also that the
speeds are based on Density Altitude, so it's worth doing the
temperature and altimeter corrections from MSL indicated.
Oh, and while getting Vy correct is crucial to getting climb
performance, correct mixture management is equally critical. Read
your POH carefully to determine when you have to run rich for cooling
purposes and when you can go for maximum power. It's worth it.
... Alex.
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\
\ Alexander Perry arperry at cts.com /
/ only write the "cts" once when replying \
\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
a. m. boardman
Personally, I'm quite happy with answers with real science behind them as
opposed to what I can find in the average private pilot text. On the
other hand, no matter how erudite someone sounds, don't forget they they
could be totally wrong, too. For instance:
pat...@DONTSPAMME.worldnet.att.net wrote:
> How many pilots know that stall speed and Vx and Vy and Vne,
> etc. all become the same at high altitude? (U2 pilots know
> it).
Perhaps it's true for a U2, but it's not even remotely true for a C172.
Vx and Vy meet at the absolute ceiling. Stall speeds is still quite a
bit lower, though, and Vne is *far* higher.
andrew
Hilton Goldstein
Isn't EAS a wonderful thing? Compressibility for the U2 means squishing up
the air. Compressibility for the 172 means squishing up the bugs (on the
rear of the aircraft?)
John T. Lowry
You asked about good propeller aircraft performance references. Here are a
few, with notes on their characteristics and academic level. The better
books for beginners, in my opinion, are near the top of the list.
1. Aerodynamics for Naval Aviators, H.H. Hurt, U.S. Navy (but fairly widely
available), 1965.
It's not possible to treat aircraft performance without covering some
aerodynamics. This book does a good job of both. Lots of good simple
graphics. Not a high level; only requires algebra. Quite complete and
authoritative.
2. Airplane Performance Stability and Control, C.D. Perkins & R.E. Hage,
Wiley (1949, but still in print; fairly expensive).
First four chapters on performance. College level; some calculus. Good
simple graphics. Contains the "general propeller chart" for predicting
thrust of (large) constant-speed propeller airplanes. I have recast that
chart using data for general aviation constant-speed aircraft, into the
so-called "General Aviation General Propeller Chart."
3. The Science of Flight: Pilot-oriented Aerodynamics, W.N. Hubin, Iowa
State University Press, 1992.
Almost a beginning physics textbook using airplanes for the examples.
Uses the Cessna 152 for many of those examples. College but non-calculus
level.
4. Introduction to Aircraft Performance, Selection, and Design, F.J. Hale,
Wiley, 1984.
A good survey of differences among propeller airplanes, turboprops,
turbojets, and turbofans, but jumps around too much for an introduction to
the subject. Uses a lot of differential calculus.
5. The Illustrated Guide to Aerodynamics, H. Smith, Tab, 1985.
A good inexpensive introduction to the performance subject. Only
requires algebra, and not much of that. A few statements need to be taken
with a grain of salt.
6. Airplane Aerodynamics and Performance, J. Roskam & C.-T.E. Lan, DAR
Corp., 1997.
A new book and a good one, used for the performance course at West
Point. Encyclopedic. So detailed the beginner may lose the drift.
7. Theory of Flight, R. v. Mises, Dover, 1959.
Somewhat dated, somewhat theoretical book which grew slowly from the
author's 1913 notes! Treatment of drag somewhat confusing because wing
profile drag is often separated out. But very complete on the atmosphere,
the engine, the propeller. And inexpensive. I still have a lot to learn from
this book.
8. Flight Theory for Pilots, C.E. Dole, I.A.P., 1989.
Don't even think about it. One of the worst books ever written, on any
subject. Except for the sections cribbed from Hurt's book (#1 above), full
of misconceptions and inaccuracies. If someone gives you a copy (as they did
me), use it to check out your personal shredder.
Since performance, per se, keeps getting interrupted by the need to know
more about the atmosphere, the instruments, basic physics, propeller theory,
how engines work, etc., etc., it would be nice if a beginner could
compartmentalize his mind and forge ahead without worrying about those
"side" issues. Unfortunately, I've never been able to. That inability makes
the learning process long and tortuous. I hope you can do better. In any
event, I hope this short bibliography helps.
P.S. Of course MY book will be better than any of these, but it's not out
yet. But don't worry. Tasteful spam (with Tabasco sauce on it?) will let you
know when that great day arrives.
John.
John T. Lowry, PhD
Flight Physics; Box 20919; Billings MT 59104
Voice: 406-248-2606
HLAviation wrote in message
<199809041400...@ladder01.news.aol.com>...
HLAviation
>You asked about good propeller aircraft performance references. Here are a
>few, with notes on their characteristics and academic level. The better
>books for beginners, in my opinion, are near the top of the list.
>
>1. Aerodynamics for Naval Aviators, H.H. Hurt, U.S. Navy (but fairly widely
>available), 1965.
> It's not possible to treat aircraft performance without covering some
>aerodynamics. This book does a good job of both. Lots of good simple
>graphics. Not a high level; only requires algebra. Quite complete and
>authoritative.
Thanks, I have ANA, It was given to me by one of my Instructors who was a
senior Aeronautical Engineer with Douglas in Long Beach. I'll check out the
others. Now how about a Mathmatics text that deals with applied mathmatics
rather than mathmatics in the abstract. Oh yeah this instructor also told me
that they had developed (I don't know to what stage) a nuclear powered rocket
decades ago, but when I questioned him about it he said he wasn't allowed to
talk about it any further. What do you think, anyy Ideas?
John T. Lowry
You're welcome (for the aircraft performance bibliography). I'm a little
at a loss to recommend an applied mathematics book. A good bet might be the
book store at a technical college. I know that these days there's a college
subject called "engineering calculus." A textbook with that title might be
what you're looking for.
[I agree that mathematics can be too abstract and abstruse to be
immediately useful, but there's a problem with getting too applied and
cookbooky -- the power of the subject comes from its abstractness and
therefore wide applicability. At Texas when I was an undergraduate there
were TWO mathematics departments, Pure Mathematics (which I took) and
Applied Mathematics. After they built Benedict Hall, Pure Mathematics was on
the third floor, Applied Mathematics on the second floor. One of my
teachers, a famous point set theorist named R.L. Moore, occasionally used to
assault students with "Mr. X, you haven't been taking courses DOWN THERE
have you?" Stabbing his forefinger downwards as though pointing to some sort
of intellectual hell.]
On the nuclear rocket, I know nothing. Another of my instructors at
Texas, Al Schild, who studied under Einstein and was co-author of a well
known tensor analysis text, used to work for Hughes Aircraft and worked on
nuclear powered airplanes. But, as in the case of your friend, he wouldn't
say anything about them. Official secrecy. I was in the submarine force and
recall that my ex-wife once got extremely angry at me when I wouldn't tell
her, years later, what the fleet submarines' test depth was.
Hope this helps.
John
John T. Lowry, PhD
Flight Physics; Box 20919; Billings MT 59104
Voice: 406-248-2606
HLAviation wrote in message
<199809050331...@ladder01.news.aol.com>...
John S. Denker
>Why does VX/VY change with Altitude?
OK, here's the real answer:
1) The key variable here is engine power. The power might change because of a
change in density altitude (at any given throttle setting) but even more
commonly it changes because you moved the throttle.
2) Let Vy(100) denote the airspeed for best rate of climb when the engine is
producing 100% of its rated power. Similarly, let Vy(0) represent the best
rate (i.e. least rate of descent) at zero power.
Contrary to what was said in some other articles in this thread, Vy(100) is
usually not much different from Vy(0). Ideally, it would not be different at
all, but typically your propeller is optimized for cruise, not for climb, so
you can get a little better performance by going faster.
Another important point: Because the power curve is rather flat on top, flying
one knot slower or one knot faster than Vy doesn't affect the rate of climb
very much.
3) The interesting case occurs when you want to climb over an obstacle. By
flying a little slower than Vy, you will have more *time* to climb before
reaching the obstacle. Therefore Vx will always be less than Vy during a
climb. At any speed above Vx, the increase in time outweighs the loss in rate
of climb you incur by not flying at Vy. However, if you fly slower than Vx,
the rate of climb is degraded out of proportion to the decrease in forward
speed. Right at Vx there is an equal tradeoff. This is illustrated by the
tangent in the figure
http://www.monmouth.com/~jsd/how/htm/power.html#fig_vx
An interesting case occurs when you have just enough power to maintain level
flight at Vy. In this case, the tangent to the power curve is horizontal, and
Vx is equal to Vy.
During a power-off descent, Vx(0) (flattest angle of glide) will actually be
*faster* than Vy(0).
You can find more discussion of this and related points at
http://www.monmouth.com/~jsd/how/htm/power.html#sec_best_angle_climb
Cheers --- jsd
To reply to me, change ".nospam" to ".com" in the address above.
John T. Lowry
Comments on your post.
John S. Denker wrote in message <6sse7u$ong$1...@news.monmouth.com>...
>In article <199809021915...@ladder01.news.aol.com>,
lmart...@aol.com (LMart59448) wrote:
>>Why does VX/VY change with Altitude?
>
>OK, here's the real answer:
>
>1) The key variable here is engine power. The power might change because
of a
>change in density altitude (at any given throttle setting) but even more
>commonly it changes because you moved the throttle.
I don't get this. In my book, both Vx and Vy, since "best," involve being at
full throttle.
>
>2) Let Vy(100) denote the airspeed for best rate of climb when the engine
is
>producing 100% of its rated power. Similarly, let Vy(0) represent the best
>rate (i.e. least rate of descent) at zero power.
>
Many call Vy(0) speed for minimum (gliding) descent (rate) Vmd
>Contrary to what was said in some other articles in this thread, Vy(100) is
>usually not much different from Vy(0). Ideally, it would not be different
at
>all, but typically your propeller is optimized for cruise, not for climb,
so
>you can get a little better performance by going faster.
>
I disagree. Say in a Cessna 172, Vmd is only a little above the stall speed,
in the low 50s KCAS, whereas Vy (your Vy(100)) is up in the mid 70s KCAS.
>Another important point: Because the power curve is rather flat on top,
flying
>one knot slower or one knot faster than Vy doesn't affect the rate of climb
>very much.
>
Right.
>3) The interesting case occurs when you want to climb over an obstacle. By
>flying a little slower than Vy, you will have more *time* to climb before
>reaching the obstacle. Therefore Vx will always be less than Vy during a
>climb. At any speed above Vx, the increase in time outweighs the loss in
rate
>of climb you incur by not flying at Vy. However, if you fly slower than
Vx,
>the rate of climb is degraded out of proportion to the decrease in forward
>speed. Right at Vx there is an equal tradeoff. This is illustrated by the
>tangent in the figure
> http://www.monmouth.com/~jsd/how/htm/power.html#fig_vx
>
This is correct, and gives nice pictures to find Vx with head winds or tail
winds, too (if not getting to be sizeable with respect to air speeds). A big
advantage of the Bootstrap Approach, though, is that with it you can
CALCULATE (accurately) Vx, Vy, Vmax, Vmin, Vbg, Vmd for any combination of
gross weight and density altitude and, with a little trial and error, even
how Vx and Vbg vary with wind.
>An interesting case occurs when you have just enough power to maintain
level
>flight at Vy. In this case, the tangent to the power curve is horizontal,
and
>Vx is equal to Vy.
>
>During a power-off descent, Vx(0) (flattest angle of glide) will actually
be
>*faster* than Vy(0).
>
In fact, for a quadratic drag polar, Vy(0) (= Vmd) is 0.76 times Vx(0) (=
Vbg). The figure is, accurately, the reciprocal of the fourth root of 3.
>You can find more discussion of this and related points at
> http://www.monmouth.com/~jsd/how/htm/power.html#sec_best_angle_climb
>
Which is an extremely good place to go!
>Cheers --- jsd
Rob Warnock
+---------------
| ... Oh yeah this instructor also told me that they had developed (I don't
| know to what stage) a nuclear powered rocket decades ago, but when I
| questioned him about it he said he wasn't allowed to talk about it any
| further. What do you think, anyy Ideas?
I know of two basic approaches (only the first of which has ever been tested):
1. "NERVA" -- A more-or-less ordinary rocket, except that it used a fission
reactor to heat a working fluid to a super-heated "steam", which went out
the back, giving thrust. If rumor serves, they actually had it powered up
and producing significant thrust a couple of times on a test stand out in
the desert somewhere. IIRC, the main problem was that you can't heat the
working fluid hot enough to get a good specific impulse without melting
the reactor core. (Oh well...)
2. "ORION" -- A more radical approach, yet simpler. The idea is to build
a *REALLY BIG* curved plate (probably out of massive amounts of armor
plate), and then throw a small A-bomb (or these days, an even smaller
laser-triggered H-bomb maybe) under it and set it off. And then in a
few minutesm do it again.... and again... The passengers & crew ride
above the plate on top of some Cheyenne-mountain-style shock absorbers.
[Think of James Blish's "Cities in Flight", but with nukes underneath
instead of spindizzies.] Somewhat fanciful perhaps (and certainly hell
on the neighborhood!), but it's claimed to be theoretically feasible.
-Rob
-----
Rob Warnock, 8L-855 rp...@sgi.com
Applied Networking http://reality.sgi.com/rpw3/
Silicon Graphics, Inc. Phone: 650-933-1673
2011 N. Shoreline Blvd. FAX: 650-964-0811
Mountain View, CA 94043 PP-ASEL-IA
Mark Mallory
: The propeller polar is a graph of CT/J^2 as a function of CP/J^2 (or vice
: versa) and, for operational propellers, is very close to linear. For
: reasons, see von Mises' Theory of Flight ca. pp. 308 ff. For typical GA
: propellers, the R^2 measure of linearity is commonly around 0.96. CT is the
: thrust coefficient of the propeller, a function of advance ratio J = V/nd, V
: air speed, n propeller circular speed, d propeller diameter. CP is the
: propeller's power coefficient function, also depending on J. There are two
: such independent functions because mechanically viable propellers move, in a
: sense, in two directions.
Several questions:
What is the relationship between CT and Thrust? Is it similar to the
relationship between CL and Lift? For example, to calculate lift, one
multiplies CL by the dynamic pressure and by the wing area. How does one
calculate the thrust produced by the prop (in lbs) for a given CT?
Similarly, what is the relationship between CP and Engine Power? How does
one calculate the CP corresponding to a particular power setting (in HP)?
Finally, what exactly is meant by saying that the plot of (CT/J^2) -vs-
(CP/J^2) is linear? Isn't this equivalent to simply saying that (CT/J^2)
is directly proportional to (CP/J^2)? (Perhaps with the addition of
a constant?)
LFransson
> Oh yeah this instructor also told me that they had developed (I don't
>| know to what stage) a nuclear powered rocket decades ago, but when I
>| questioned him about it he said he wasn't allowed to talk about it any
>| further. What do you think, anyy Ideas?
I read in Popular Science several years ago about something similar. It was a
nuclear ramjet-powered cruise missile. Just a bare core that heated the
incoming compressed air to provide thrust. The obvious consequence of such an
arrangement was that it would cook anything it overflew, so the strategy was to
have the missle zig-zag across the enemy countryside before finally striking
its target. I believe it flew once in testing, but I'm not sure.
Larry L. Fransson - ATP (CE-500), CFMEII
Macon, Georgia
"Pilots are just plane people with a different air about them."
John T. Lowry
Several answers to your latest.
1. T = Rho*n^2*d^4*CT, where T is thrust, Rho is air density, n is
propeller circular speed, d is prop diameter, and CT (should be C-sub-T!) is
the thrust coefficient. Use British Engineering units throughout.
2. P = Rho*n^3*d^5*CP, where P is power (ft-lbf/sec, it takes 550 of
them to make an HP) and CP is the power coefficient.
So yes these are dimensionless coefficients, much the same as lift
coefficient CL or drag coefficient CD. There have been several different
defintions over the years, but the above are most common.
3. "Linear" means (geometrically) that when you plot one variable
against another, on regular rectangular grid graph paper, you get a straight
line. In each such relationship, two constants (which are often taken to be
given variables 'm' and 'b') are involved. I do the same.
The important point is that the Bootstrap Approach is not some ersatz
curve-fitting approach to predicting performance. Simple climb and
full-power level runs are made to find the values of m and b and, from that
point, it's just calculation. m and b, while found empirically through
simple flight tests, can be expressed in terms of important things about the
airplane and its behavior.
The overall procedure, in outline, is: 1. You do the flight tests, then
calculate a little to find m and b (also parasite drag coefficient CD0 and
airplane efficiency factor e, from glide tests). 2. You then have 9 numbers
(wing area S, aspect ratio A, CD0, e, rated MSL torque M0, power dropoff
parameter C (C = 0.12, essentially, for modern engines), d, m, and b).
[There is an extra flight test to accumulate data for partial throttle
operations, but I'll skip that for here and now.] From the nine numbers,
making up the so-called "Bootstrap Data Plate," you can easily calculate --
when put together with the pilot-chosen operational variables for density
altitude, air speed V, and bank angle phi -- thrust, drag, power available
or required, rate or angle of climb or descent, all the steady-state flight
performance numbers for the airplane. Also the weight and altitude
dependence of the main V speeds: Vx, Vy, Vbg, Vmd, Vmax, Vmin. Not stall
speed Vs, but you've got that anyway, or can find it from its own flight
tests.
The Bootstrap Approach is used by some of the more advanced kitplane
manufacturers and, at least in one case, for primary category certificated
aircraft also. The advantages, over "standard" techniques are twofold: (1)
The Bootstrap Approach takes less than 5% the time of the standard
performance flight test techniques while giving FULL information far beyond
the GAMA format POH performance section, and (2) If you say decide to change
an engine, keeping everything else the same, you only need to switch two
numbers in the Bootstrap Data Plate and recalculate. The Bootstrap Approach
splits the airplane into 3 separate (though of course interacting) systems:
airframe, engine, and propeller. Making changes to one of those three
systems only requires refiguring the Bootstrap parameters pertaining to that
system.
I won't go into the partial throttle portion of the theory because it's
somewhat more complex. But, in summary (we're painting the house and I've
gotta run) the Bootstrap Approach will let you win the following bet:
See that (fixed-pitch propeller) airplane out on the tarmac? Go fly it
for an hour, never going over 5000', then come back and tell me precisely
how you would (for instance) make a descending standard rate turn, at 10000
ft at 2250 pounds, at 300 ft/min descent rate and at 90 KCAS! Anyone can
figure the required bank angle, but no other performance theory can tell you
the RPM required.
Hope this helps.
John.
John T. Lowry, PhD
Flight Physics; Box 20919; Billings MT 59104
Voice: 406-248-2606
Mark Mallory wrote in message ...
>John T. Lowry (jlo...@mcn.net) wrote:
>: The propeller polar is a graph of CT/J^2 as a function of CP/J^2 (or vice
>: versa) and, for operational propellers, is very close to linear. For
>: reasons, see von Mises' Theory of Flight ca. pp. 308 ff. For typical GA
>: propellers, the R^2 measure of linearity is commonly around 0.96. CT is
the
>: thrust coefficient of the propeller, a function of advance ratio J =
V/nd, V
>: air speed, n propeller circular speed, d propeller diameter. CP is the
>: propeller's power coefficient function, also depending on J. There are
two
>: such independent functions because mechanically viable propellers move,
in a
>: sense, in two directions.
>
Capt. Zombo
lfra...@aol.com (LFransson) wrote:
+ In article <6sto5g$4f...@fido.engr.sgi.com>, rp...@rigden.engr.sgi.com wrote:
+
+ > Oh yeah this instructor also told me that they had developed (I don't
+ >| know to what stage) a nuclear powered rocket decades ago, but when I
+ >| questioned him about it he said he wasn't allowed to talk about it any
+ >| further. What do you think, anyy Ideas?
+
+ I read in Popular Science several years ago about something similar. It was a
+ nuclear ramjet-powered cruise missile. Just a bare core that heated the
+ incoming compressed air to provide thrust. The obvious consequence of such an
+ arrangement was that it would cook anything it overflew, so the strategy
was to
+ have the missle zig-zag across the enemy countryside before finally striking
+ its target. I believe it flew once in testing, but I'm not sure.
+
...thank you for continuing to perpetuaute the public's general
level of hysteria over anything "nuclear".
Yes, DOE was developing nuclear powered rocket engines in the late 1950's
through the 1960's. The program was called "Project Rover" and was part
of the more ambitious effort to explore deep space beyond the moon. The
project was abandoned in 1969.
The tests were conducted the desert north of Las Vegas at NTS Area 25.
Pieces of the test stand from those experiments still exist today. The
test demonstrated that the concept would work, but the subsequent radiation
was deemed too high for the idea to be practical.
Perhaps there are similar designs for other engines, but the idea
that DOE/NASA/DoD actually flew one is as ridiculous as the notion
that an exposed core is going to "cook anything it overflew".
If you want to read more about the program, here's a good place
to start....
http://www.nv.doe.gov/news%26pubs/publications/historyreports/news%26views/nrds.htm
Mark Mallory
: somewhat more complex. But, in summary (we're painting the house and I've
: gotta run) the Bootstrap Approach will let you win the following bet:
: See that (fixed-pitch propeller) airplane out on the tarmac? Go fly it
Does the BS Approach still work if I have a Constant Speed prop?
John T. Lowry
Bootstrap Approach with a constant-speed prop? Yes and no. There is a
chapter, in the "field guide," on dealing with constant-speed props. But the
theory is not simply and analytic, as it is with fixed-pitch props. Instead,
a complicated curve-fit graph called the "General Aviation General Propeller
Chart" is used. In another sense the constant-speed version is simpler in
that one only needs to use (assuming they're correct) POH performance values
of % power, manifold pressure, and RPM at given density altitude. (I think
those are generally correct because the manufacturer, unlike the cases of
maximum level flight speed, best rate of climb, etc., here has no reason to
"mislead.") The CP you get from that, plus geometric propeller data you get
from some careful one-time measurements on the propeller, let's you get
propeller efficiency. With the spreadsheet templates on the "companion"
disk, all this is automated.
To understand the theory and how it works, I usually suggest pilots
start with the fixed-pitch version because there's only some relatively
simple formulas to deal with.
John.
John T. Lowry, PhD
Flight Physics; Box 20919; Billings MT 59104
Voice: 406-248-2606
Mark Mallory wrote in message ...
>John T. Lowry (jlo...@mcn.net) wrote:
>: I won't go into the partial throttle portion of the theory because
it's
>: somewhat more complex. But, in summary (we're painting the house and I've
>: gotta run) the Bootstrap Approach will let you win the following bet:
>
>: See that (fixed-pitch propeller) airplane out on the tarmac? Go fly
it
>
Herman L. Price
> | know to what stage) a nuclear powered rocket decades ago, but when I
tested in the deserts north of Vegas in the late fifties/early sixties.
The Orion concept is much simpler (in principle). The company which
owns (or owned, not sure on the status) the patent on this built and
tested a small scale version using conventional explosives. It flew
well, although reportedly it was incredibly loud, maybe even louder than
a V22 Osprey ;-).
I think the company was AVCO and the tests were in the late seventies or
early eighties.
For an excellent if fictional discription of both riding and being
relatively near the liftoff point of a full scale Orion vehicle see
"Footfall" by Niven/Pournelle.
Herman Price
"Think Big . . .Remember, A Ringworld is just a Dyson slice."
Steve Peltz
Todd Pattist <pat...@DONTSPAMME.worldnet.att.net> wrote:
>First, the U2: flutter is more related to TAS than CAS, and
>flutter problems may be the limit that sets Vne. Stall
Flutter vs. TAS is why in many sailplanes Vne (which is in IAS or CAS)
is reduced at higher altitudes. My understanding was that the specific
problem in the U2 was with exceeding Mach 1. At a certain point, you
couldn't even turn, both because the stall speed increased above Mach
1 and because the outside wing tip would be going too fast. I believe
the phrase used to describe that point on the performance charts was
"coffin corner".
I agree with Todd. John's analysis of things are almost always worth
figuring out, even if you have to re-read them several times.
John T. Lowry
We've gotten off onto absolute ceilings, so I thought you might be
interested in the following Bootstrap formulas which let one predict
absolute ceiling (for a given weight W) in terms of the "absolute" ceiling
when banked and/or at partial throttle. The formula for relative power
setting PI is somewhat complicated, so while I'll include that parameter I
won't say, here, how to find it.
Everything having to do with absolute ceilings depends on power dropoff
factor PHI = (Sigma - C)/(1-C), C about 0.12 for all modern aircraft
reciprocating internal combustion engines.
PHI,AC(W,PI,Phi) = (1/PI*cos(Phi))*PHI,AC(W,PI=1,Phi=0), where
AC stands for 'absolute ceiling', Phi is bank angle. Sigma is of course
relative air density.
Now the (single) calibrate air speed for absolute ceiling is
V,CAC(W,PI,Phi) = sqrt(W/(WB*cos(Phi)))*V,CxB, where
CAC stands for calibrated at "absolute" ceiling, WB is a base weight
(normally we use maximum gross weight) and CxB mean calibrated air speed for
best angle of climb (which doesn't vary with altitude) at the base weight
WB.
The point is: you can go up to say 6500 feet, at full throttle, bank
enough so that no matter what air speed you pick you can just barely stay
level, record all that, then come back down and figure your absolute
ceiling.
John.
--
John T. Lowry, PhD
Flight Physics; Box 20919; Billings MT 59104
Voice: 406-248-2606
Todd Pattist wrote in message <35f62970...@netnews.worldnet.att.net>...
>a...@bronze.lcs.mit.edu (a. m. boardman) wrote:
>
>>> How many pilots know that stall speed and Vx and Vy and Vne,
>>> etc. all become the same at high altitude? (U2 pilots know
>>> it).
>>
>>Perhaps it's true for a U2, but it's not even remotely true for a C172.
>>Vx and Vy meet at the absolute ceiling. Stall speeds is still quite a
>>bit lower, though, and Vne is *far* higher.
>
>Andrew, it wasn't meant to be true for a 172 operated in
>normal conditions. It was meant to point out that math and
>science can help us understand what happens outside our
>normal boundaries.
>
>First, the U2: flutter is more related to TAS than CAS, and
>flutter problems may be the limit that sets Vne. Stall
>speed is more related to CAS than TAS. This means that at a
>very high altitude, for some aircraft, stall speed is Vne,
>and the other speeds between them are also the same. I'm
>told that happens in a U2 - next time I fly one, I'll
>confirm it :-).
>
>Next the 172: What happens at 20,000? What happens at
>30,000'? What is stall speed? What is Vne? Discussions
>with the physics of aviation in them (like John's posts) can
>help us understand what's going on and prepare us for new
>aircraft, and new situations, and sometimes give us answers.
>As for those who are going to tell me that nothing they fly
>ever goes that high, I can confirm at least one 172 that has
>gone above 25,000'. Heck, I was flying locally in a
>sailplane and went to 15,000 feet two days ago in New York,
>catching the wave off the Catskills. In NH, I've been above
>30,000', and in CO, flights between 40,000' and 50,000' are
>not unheard of. If a sailplane can do it, so can a
>powerplane.
>
>
>
>Todd Pattist
>(Remove DONTSPAMME from address to reply.)
Peter Gottlieb
be taken from the lunar surface? Do I remember this correctly or am I
just repeating BS?
Herman L. Price wrote in message <35F514...@eaze.net>...
>Rob Warnock wrote:
>>
>> HLAviation <hlavi...@aol.com> wrote:
>> +---------------
>>
Rob Warnock
+---------------
| lfra...@aol.com (LFransson) wrote:
| + rp...@rigden.engr.sgi.com wrote:
| +
| + > Oh yeah this instructor also told me that they had developed (I don't
| + >| know to what stage) a nuclear powered rocket decades ago, but when I
| + >| questioned him about it he said he wasn't allowed to talk about it any
| + >| further. What do you think, anyy Ideas?
| +
| + I read in Popular Science several years ago about something similar. It was a
| + nuclear ramjet-powered cruise missile. Just a bare core that heated the
| + incoming compressed air to provide thrust. The obvious consequence of such an
| + arrangement was that it would cook anything it overflew, so the strategy
| was to
| + have the missle zig-zag across the enemy countryside before finally striking
| + its target. I believe it flew once in testing, but I'm not sure.
| +
|
| ...thank you for continuing to perpetuaute the public's general
| level of hysteria over anything "nuclear".
Note that somebody [not saying who] got the attribution of the
quotes mixed up. I did not write *any* of the text quoted above.
Rob Warnock
+---------------
| What about the talk of ion propulsion, possibly using fine dust that could
| be taken from the lunar surface? Do I remember this correctly or am I
| just repeating BS?
Ion propulsion is still being considered, especially for very-long-range
missions (e.g., interstellar) where you want the highest-possible specific
impulse. But there is nothing about ion rockets that in any way depends
on nuclear energy per se (other than perhaps as one option among many as
a source of electricity), so that's why I didn't bother to mention it in
a thread on "nuke rockets".
LFransson
I wrote:
>| + I read in Popular Science several years ago about something similar.
> It was a
Someone responded:
>| ...thank you for continuing to perpetuaute the public's general
>| level of hysteria over anything "nuclear".
I guess that I should have added that it never went beyond testing, as it was
deemed impractical in actual use.
I wasn't attempting to "perpetuate the public's general level of hysteria over
anything nuclear." I was simply replying to a previous post and stating what I
had read several years ago. If I could go back and dig up that particular
issue of the magazine, I would cite it verbatim. I tried to find it, but I was
unable.
I'm well aware of the public's general distrust of anything nuclear. I spent
five years on active duty in the Navy operating nuclear reactors. I never do
or say anything with the intention of raising anyone's "level of hysteria."
Have a nice day.
Harvey Irby
Site in the early 1980's.
All of the nuclear aircraft and rocket engine programs were shut down by
then and the test facilities were in the D&D (Decommissioning and
Decontamination) stage. I believe the last live rocket engine was tested in
1973. I worked at the EMAD (Engine Maintenance, Assembly, and Disassembly)
facility which was the world's largest nuclear hot-bay facility (essentially
an aircraft hanger with six foot thick walls). Below are my best
recollections.
The oldest program (started in the 1950's) was the TORREY (I don't know the
meaning of the acronym) which was to be a nuclear ram-jet. The intended
strategic bomber aircraft would have both conventional turbo-jet and nuclear
engines and could go around the world non-stop. Air-to-air refueling was
not a safe and proven concept at that time. The nuclear engines would only
operate at cruising altitude and the crew would be protected by distance and
shadow shielding. There would be enough shielding around the engines to
protect the ground crews when the engines were shut down and additional
portable shielding would be added when the aircraft was parked. The B-52
and KC-135 tanker made in-flight refueling and world wide strike capability
a no-sweat operation and killed TORREY.
The early nuclear rocket programs included KIWI and ROVER (ROcket Vehicle
Experimental Reactor) which proved the nuclear heated hydrogen rocket
concept and lead to the NERVA (Nuclear Engine for Rocket Vehicle
Application) program. The two missions identified for NERVA were the
Earth/Moon Shuttle and the Manned Mars Mission. These engines were only
intended to be fired in space and would be carried to orbit by something
like the Space Shuttle and would then be mounted on large space vehicles
built in orbit. When the engine reached the end of its life, it would be
fired one last time into the sun.
When the US Space Program was sharply curtailed in the early 1970's, all
manned deep space programs were cancelled and the NERVA with them. I
understand the NERVA still has the highest specific impulse of any large
rocket engine design.
These programs are all now unclassified NASA/DOE/DOD research.
LFransson wrote in message
<199809091932...@ladder01.news.aol.com>...