Conference 7.286::space

608.0. "Space Shuttle Development - A retrospective" by 4347::GRIFFIN (Dave Griffin) Fri Apr 13 1990 14:11

Article 18295 of sci.space:
Path: shlump.nac.dec.com!decuac!haven!aplcen!uakari.primate.wisc.edu!zaphod.mps.ohio-state.edu!sdd.hp.com!elroy.jpl.nasa.gov!zardoz.cpd.com!dhw68k!ofa123!Wales.Larrison
From: [email protected] (Wales Larrison)
Newsgroups: sci.space
Subject: Space Shuttle Development
Message-ID: <[email protected]>
Date: 12 Apr 90 01:42:51 GMT
Organization: Universal Electronics Inc. (Gateway)


  Someone on the net has asked for some references for past shuttle
design studies.  A couple of years ago I was digging into the design
ofthe space shuttle system, and had a couple of references folks might
find useful.
 
  Simplest, most accessible references, which cover a good range of
the overall technical and political decisions that went into the Space
Shuttle design decisions:
    "Enterprise" by J. Grey (avail in most large public libraries)
    "The Decision to Develop the Space Shuttle", by J.M. Logsdon,
Space Policy, May 1986
    " The Space Shuttle Program: A Policy Failure?", Science, 30 May
1986
    "Engineering Design and Political Choice: the Space Shuttle 1969-
1972", by S. Pace (yes, the "Great Satan" himself), published as an
AIAA historical paper 1984, and as a MIT master's thesis, 1982
    2 articles by C. Barfied in "National Journal", 12 and 19 Aug 72
 
  Other good articles:
 
    "Evolution of the Space Shuttle Design", by J.P. Loftus, S.M.
Andrich, M.G. Goodhard, and R.C. Kennedy
    "The Space Shuttle - Some Key Program Decisions", by R.F.
Thompson (1984 Von Karman Lecture)
    "Progress of manned space flight from Apollo to Space Shuttle", by
A. Cohen (1984 Von Karman lecture)
    "The Space Shuttle Focused Technology Program: Lessons Learned"
Aeronautics and Astronautics,  Feb 1983
 
  If the forum will indulge me, I'd like to also add a few more
comments on the design process that was followed.  This is synopsized
from the above articles, plus some more digging I've done on my own
into the data available (including requesting and reading a fair num-
ber of the supporting contract reports, study assessments, economic
analyses, and industry proposals - plus talking to some of the key
participants).
 
  NASA typically follows what is known as a "Phased Development"
program.  The rules for this are outlined in OMB circular A-109.
Typically, there are initial small technology studies and small design
studies.  To begin the process, a Phase-A study is let for "Concept
Exploration", which tries to establish if a concept is feasible, and
what its primary design constraints and requirements might be.  A
Phase-B Study is next, which focuses on a "Preliminary Design" for a
selected concept to meet the design requirements established in Phase
A.  Critical technologies should be identified and demonstrated.
Finally a Phase C/D "Design, Development, Test, and Engineering"
contract is awarded, which leads to a flight article.
 
  To scope this effort, there are about 100 Phase A studies awarded
forevery Phase C/D, since not every conceptual idea is ever pursued.
Typical Phase A studies range from $100K to $5M or so, and take up to
a couple of years to complete.  Phase B studies have at least 2
competitors, usually take 1-2 years to complete, and range in the $5-
$50 million range.  There is usually only 1 winner of Phase C/D
contracts, but the loser may be brought in later, as a "second source"
or as a contractor for some parts of the overall system, if their
design is superior in those areas (as was done with the F-16 and F-18)
 
  From the documentation I have, Space Shuttle design studies began in
about 1968, with studies by MDAC of a Gemini-derived 9-12 man
spacecraft ("Big-G") for resupplying a space Station.  In the heady
days after the first moon landing, NASA and the administration had
mapped out an overall plan for future space activities which included
Space Station, a Lunar Base, Manned Mission to Mars, continued use of
the Saturn-series of Rockets, and a Space Shuttle.
  Ref: "America's Next Decade in Space: A Report for the Space Task
       Group", NASA, Sep. 1969
 
  To gather more insight into what it would take to accomplish this
ambitious plan for space activities, NASA began a series of Phase A
and technology studies.  (It should be noted this included Phase A
studies of Lunar Bases, Saturn-derived launch vehicles, Manned Mars
Missions, and Space Stations, among others).  They let four Phase A
contracts for "Integrated Launch and Reentry Vehicle" studies,
totaling $1.8 M, in 1969.  These included:
   o McDonnell-Douglas Astronautics Company (MDAC), contract NAS 9-
9204 (with LaRC) of a HL-10 body shape with a straight wing and
25,000 lb payload.
   o North American Rockwell (NAR), contract NAS 9-9205, (with JSC)
of a straight wing vehicle with a 50,000 lb payload.
   o Lockheed Missile and Space Corporation (LMSC), contract NAS 9-
9206, (with MSFC) for a 1 1/2 stage vehicle with a double delta wing,
launched in a triamese configuration.  (This is later redirected to 2
stage fully reusable configuration, as the triamese proved unstable.)
  o General Dynamics (GD), contract NAS 9-9207, (with MSFC), of a
triamese vehicle configuration with a two-element swing wing and
50,000 pound payload.
  Martin Marrieta performed a parallel study effort under company
money (they had lost the Phase A competition), which followed the same
schedule, of a launcher with a 36,500 pound payload called the
"Spacemaster".
 
  In parallel, and based upon the results of these Phase A study
contracts, NASA (At JSC, MSFC, and LaRC) studied a series of
alternative conceptual designs and performed system sizing studies
(contractually supported by MDAC), including a "DC-3 Shuttle"
design supported by Vought aviation.

  Each of the major aerospace contractors also funded and ran their
own conceptual design and costing exercises, in parallel with their
contractual efforts.  The estimates of these company investments come
to about $120 million over the 1968-1970 time period.  Unfortunately,
much of the data supporting these industry studies is lost, excepting
conclusions and summaries of the results.
 
  In 1970, NASA let 4 basic Phase B Contracts for a total of $30M,
over a 1 year period.  Each contractor submitted about 500 pages of
technical and cost analyses supporting their proposal.  Proposals
were submitted from:
  o Lockheed/Boeing (teamed with TWA, AC Electronics Division, Bell
Aerosciences, Bendix Navigation, and Messerschmitt-Boeklow-Bolm)
  o Grumman (teamed with General Electric, Northrup, Aerojet General,
and Eastern Airlines)
  o MDAC (teamed with Martin Marietta, TRW, PanAm, Raytheon, and
United Aircraft Norden Division)
  o North American Rockwell/General Dynamics (teamed with American
Airlines, Honeywell, and IBM)
 
  Two proposals were selected (MDAC and NAR), each company team to 
study a fully reusable system, with both a high (1100 nmi) and a low 
(600 nmi) cross range orbiter, carrying a 40,000 pound payload.  Each
was funded at $20 M 
    MDAC, contract number NAS 8-26016 (with MSFC), 1970
    North American Rockwell, contract NAS 9-10960 (with JSC), 1970
 
  However, budgetary impacts and external politics began to affect the
system.  As studies of the Space Station and fully reusable shuttle
continued, it became clear to pursuing the Space Station and Space
Shuttle as a first step towards longer term objectives (such as the
lunar base and Mars mission) would require more than a doubling of
NASA's annual budget for some years.  This was felt to be unrealistic
due to the current budget crunch needed to support increased military
expenditures in Southeast Asia and the continuing expansions of
programs from "the Great Society" begun in the mid-1960's. (Note:
NASA's space budget had peaked at $5.9 billion in 1966, and by 1970
had declined to $3.5 billion.)
  During Congressional Review of the NASA 1971 budget, it was stated
that NASA should first build the Space Shuttle over the Space Station
because if they could not be developed simultaneously, the Shuttle
could act as a surrogate station in extended orbital missions, and the
establishment of the space shuttle was necessary for cost-effective
logistics support of a space station.  This decision was bumped to the
highest level in the administration to President Nixon, by his top
domestic policy advisor John Erlichman.

   A detailed independent economic analysis of the Shuttle program was 
prepared, at the request of Congress. This was made by an outside, 
non-aerospace consulting firm.  This was a pivotal step, in that it 
forced NASA to identify the Shuttle as the primary means of performing 
a variety of roles for NASA, DoD, and other users; and forced NASA 
into a public justification of the Shuttle on near-term financial 
grounds, when other reasons for such a system were more fundamental 
(as part of a long term American space strategy).  NASA now had to get 
DoD assurances it would use the shuttle for all its launches and began 
designing to meet all DoD launch requirements.  NASA was forced to 
show Congress and the Administration how any system selected would be 
cheaper than any alternative launch system.  Results from this 
economic analysis would be used as the rationale to "phase out" other 
launch systems. 
    "Economic Analyses of New Space Transportation Systems", 
     Mathematica, Inc., 2 volumes, May 1971   
  At this point, NASA stopped providing strategy for future space 
programs, and began a long series of tactical battles focusing on 
narrower and narrower budgetary battles. It had to meet strict 
economic criteria imposed by OMB (who maintained an independent 
shuttle system design group), and was encouraged to design a shuttle 
that could "do all things and be all things" to all users to get the 
maximum cost effectiveness.  This made it very difficult to accept 
suggestions for smaller, less capable, and less risky shuttle systems,
or to accept the added costs of parallel development programs which 
could reduce technical risks. 
  While the two stage fully reusable configuration was the option 
offered the lowest potential cost per flight (as shown by all of the 
Phase A studies), the overall cost to develop the system was attacked 
by Congress and OMB.  Other options for the Space Shuttle 
configuration had to be examined. 
  In parallel to the Phase B contracts, Grumman and Lockheed were 
given supporting contracts to study "Alternative Space Shuttle 
Concepts" which included a 1 1/2 stage thrust-augmented system, a 
solid booster/reusable orbiter system, reusable booster and orbiter 
system, and a minimum risk fully reusable system.  This was done as 
extensions to their Phase A studies, and essentially were parallel 
Phase B studies to the fully reusable system selected.  Each was 
funded at $14 M. 
    Lockheed, contract NAS 8-26362 (with MSFC), 1970
    Grumman, contract NAS 9-11160 (with MSFC), 1970
 
  It should be noted that numerous parallel technology studies were 
being performed.  These included a foamed silica coated borosilicate 
glass studied for a reusable heat shield (which offered a 10:1 weight 
reduction and greatly decreased costs over metallic thermal protection 
systems), reusable cryo tankage, advanced materials, and cryo engines.

  At the end of the formal Phase B studies in 1971, several 
conclusions were reached.  Primary among them was that the 2 stage, 
fully reusable system had a high development cost, required multiple 
concurrent technology developments, and had a relatively high 
technology risk.  Development costs could exceed $2 billion at the 
peak year.  The political feasibility of the 2 stage fully reusable 
design ended when, in 1971,  the OMB capped the NASA budget for all 
programs not to exceed $3.2 billion, and would not increase this 
level in the foreseeable future. 
  An alternative configuration studied in the Phase A extension 
studies using an expendable external fuel tank was felt to have lower 
development costs and lower technology risks.  However, this decision 
bumped the Phase B studies back to the starting point.  All of the 
Phase B studies were extended for another year.  NASA baselined the 
external tank approach in August 1971 and began to look at variations 
on the differing booster and shuttle designs to reduce the system 
development costs, while still getting as much utility out of the 
vehicle as possible. 
   An external fuel tank, by putting more than 80% of the mass that 
was to be accelerated into a flexible design envelope, reduced the 
system sensitivity to the critical uncertainties of orbiter inert 
weight growth, and main engine performance shortfall.  While these 
design factors had been massively analyzed, the system design was 
found to be very sensitive to these.  Since all uncertainties could 
not be eliminated without actually building and testing a system (and 
there was no money for doing this), NASA chose to pick a system that 
was the least sensitive to these uncertainties. This approach however, 
complicated the operations, and increased the recurring cost. 
  (Note: using 20:20 hindsight, the engine performance has technically 
been right on.  Engine recurring cost has exceeded its expected 
levels, since the approach taken was to not risk performance in favor 
of lower costs.  Similarly, the orbiter inert weight has grown 
approximately 2 % over the expected weight set in 1971 - primarily due 
to uncertainties in the aerodynamics and aerothermal environments.  
Prior to the shuttle, the X-15 had provided data up to about Mach 7, 
but the entry environment from Mach 7-25 was pretty much unknown, and 
almost impossible to simulate on the ground.  Again, the decision was 
made to design heavier structures and less maintainable systems to 
encompass the range of these uncertainties - reducing the development 
risk and cost, while increasing the recurring costs from continuing 
operations.  NASA's priority was not on the operational 
characteristics of the vehicles - and this would come back to haunt 
them in complex and high cost operations for the system. 
  For Booster design, the reusable booster design had been ruled out 
as too expensive to develop (although everyone involved agreed it 
would be cheaper to operate flight-to-flight).  After several design 
iterations, a design emerged based upon Grumman and MDAC analyses 
which used an expendable booster burning in parallel to the orbiter 
during first stage flight. It seemed to provide the most capability, 
with the minimum development cost, although every assessment showed it 
had a higher recurring cost. 
  Cost awareness was very apparent at NASA.  NASA's guidelines in 
August 1971 included:
  "o Don't exceed much over $1 B in any year
   o Keep total costs below $12 B for 445 flights
   o Keep Risks Low - don't do a great deal more than we have 
     demonstrated before 
   o Keep flexible to vary costs with traffic demands"

  NASA's cost data base was extensive, based upon up to 6 independent 
cost analyses designs for similar systems, and very specifically 
showed the differences in vehicle configuration and recurring cost 
from limiting development costs. 
     (Example data shown from summary contractor data...) 
   [Summary Data from 3 August 1971 JSC internal report] 
Grumman Concepts - all 1 1/2 stage, thrust augmented systems.
 
                  Expendable   Expendable     Expendable     Reuse  
                  Liq Booster  Liq Booster    Solid Bstr     Orb & 
                  (Reuse Cryo  Reuse Orb      Reuse Orb      Booster  
                   Tanks)
                  Reuse Orb
DDT&E ($M)
  Orbiter           2,600       2,615           2,615         2,586
  Booster/SRM         153         537             338         2,724
  Reuse Cryo Tanks    301
  Main Engine         657         769             657           655
  Flt test            651         693             664           936
    Total           4,362       4,614           4,274         7,079
 
 
Production ($M)
  Orbiter             482         544             544           491
  Booster/SRM       1,369       2,612           5,644         1,121
  Tanks             2,259
     Total          4,110       3,156           6,188         1,612
 
Operations            998       2,131           1,105         1,475
 
Total Program       9,470       9,901          11,567         9,988
 
Peak Annual         1,100       ?????           1,100         1,640
 Funding
 
Direct Cost          9.82       10.26           14.66          3.23
 per Flight
 
Note:(translating from 1971 dollars to 1990 dollars, yields a cost per 
flight of           35.84       37.45           53.51         11.79 
these were for a 40,000 pound payload system, and yielded a cost per 
pound (1990$) of    $896        $936            $1338         $295  ). 
 
  NASA still had not been given the official go-ahead for shuttle 
development, although the primary decision had apparently already been 
made in the White House.  In a calculated measure, NASA was forced by 
OMB to go through repeated attempts to reduce the Shuttle development 
costs.  (Ref: Pace, Logsdon)  Casper Weinberger, Deputy Director of 
the OMB, told his staff that they had a free hand to work on NASA to 
reduce program costs.  Through November and December of 1971 OMB and 
NASA fought over the shuttle design and configuration (despite all of 
the previous contracted studies and study results).  To force NASA to 
consider smaller, lower-cost shuttles, OMB kept specifying specific 
designs to be evaluated by NASA, and NASA kept arguing against the 
technical ability of OMB to cost-design a shuttle system. 

  It was not until 3 January 1972 that the final approval for the 
Space Shuttle was communicated to NASA.  Appropriately enough, NASA 
had spent the holidays struggling to answer another set of detailed 
OMB questions, and had set a 14x45 foot payload bay as the minimum 
size for the shuttle.  To NASA's surprise, they were told the 15x60 
foot payload bay had been approved. 
  The decision to use solid rocket motors for the booster stage was 
made soon afterwards.  As part of the extensions of the Phase B 
contracts, numerous booster propulsion schemes had been examined. The 
major reason for the choice of solid rocket boosters was the 
development cost of the liquid boosters.  NASA specifically chose to 
accept a higher recurring cost and a complex operations flow, to 
reduce the projected development cost.  Reusable cryo tanks were also 
rejected on the basis of a higher development cost and increased 
technical risk, although they had a lower recurring cost.  OMB 
director George Schultz said "NASA is to be congratulated for its 
willingness to examine a wide range of alternatives to find a 
configuration which retains system capability but which reduces the 
amount of investment required." (Ref: Letter from George Schultz to 
Jame Fletcher, 17 March 1972, NASA historical archives) 
 
  In March of 1972, a "request for proposals" was released to the 
industry for the specified space shuttle system.  It had all of the 
elements of the current design - 15X60 payload bay volume, cross range
of 1100 nmi, 65,000 pound payload capability, large external tank, and
dual solid rocket boosters.  4 teams of companies replied - each with 
a proposal of 2000+ pages. These were MDAC, Grumman, North American 
Rockwell, and Lockheed.   Of these, North American Rockwell was 
chosen, and contract NAS 9-14000 to design, develop, test, and 
construct the space shuttle was let in late 1972. 
 
   Between 1972 and 1980, the funding profile for the program changed 
dramatically - annual budgets for the phase C/D contract effort 
changed yearly.  Each year the effort had to be replanned and rephased
by NASA and the contractors.  The expected 5 year contract was 
stretched by Congress to 7, then 9 years.  The number of vehicles to 
be built changed from 10 (1972) to 5 (1975)  to 4 (1976) to 1 (1977) 
to 4 (1978) again, and the delivery schedule stretched out.  Each year
the contracts for delivery of parts and materials had to be 
renegotiated with subcontractors and vendors.  This doubled or tripled
the expected program costs.  (Rockwell claimed after 51-L that a block
buy of 3 orbiters can be made for the price of 2 - if the dollars are 
allocated up front).  
   Meanwhile, the NASA budget continued to shrink.  In constant 1972 
dollars, the NASA budget shrank from $3.2 billion in 1971 to $2.4 
billion in 1978.  As the budgets decreased, new programs that had been 
expected to provide the majority of the payloads to be carried on the 
shuttle were eliminated or severely cut back.  Since these programs 
were not yet established, or not even in existence, they could not 
defend themselves against budget cuts. This created the vicious spiral
of: few missions - high cost transportation - high cost missions - 
more importance on fewer missions - fewer, more costly missions - 
higher cost transportation - ... 
 
  And it is from this "death spiral" that we are trying to extract our
national space program.  The Challenger accident, the failure of the 
few alternative launch systems, and the increased attention given to 
space by the public are all working to extract us from this.  
   Hope you folks find this interesting.  I had fun putting it 
together. 

    Yes,  Very interesting. Once again I wonder Why congress never
    seems to aprove a program up front but has to go tru this yearly
    fight cycle that costs so much of congresses time, and tax payers
    money.
    
    The thing to do, would be to aprove it all in one shot. And to
    consider the price of the hole program from birth to dead. Instead of
    just considering the totals year by year. (I guess they are afraid to
    spend to much in any single year).
    
    But logicaly I am tired of this as an american and a tax payer.
    It costs us money and time over the long run. I ressent the lost of
    time even more then I do the loss of money.
    
    I want to see bases on the moon and mars at least before I die.
    And well as the maned exploration of the rest of the solar system
    
    Gil

  If NASA had given Congress a single proposal with what turned out to be the
correct price of the shuttle it would never have been built. Most likely
with out the Shuttle, we would never have seen an X-30 or Space plane.

  During the 70's, spending on space programs was very unpopular. It's a little
better now but not much. In spite of the empty promises by George Bush it's not
likely that NASA will get enough money to move quickly with any new programs. 

  Unless things change a lot and unless tax payers become a lot more generous,
which doesn't seem likely, it will be a long time before we see a space effort
like we saw during the Apollo days. 

  George

The latest orbiter (Endeavour) is being built with a multi-year contract
from NASA.  Rockwell is reportedly on schedule and under budget with it's
construction.

Funding is not the only reason this is happening though - the design for
the orbiter is stable and Rockwell isn't getting ECO's every 10 seconds
for it -- this would not be true during the initial production run.  Rockwell
also has a cost incentive program in place (popular with Rockwell, not with
Congress).

What really hurts is that we could have ordered two orbiters for nearly the
price of one (sorry, hearsay - I don't have references).  Rockwell pitched
this option, but I'm sure that it was Congress that turned it down (I find
it hard to imagine NASA pooh-poohing a 5th orbiter in the "fleet").

Anyway, there seems to be some proof that multi-year funding can help save
money over time -- even if the congressmen don't like it.

- dave

RE:               <<< Note 608.3 by 4347::GRIFFIN "Dave Griffin" >>>

All of the major airframe components for Endeavor (OV-105) were built before
the Challenger Disaster as structural spares.  Thus much of the cost for
Endeavor was paid during the late 1970's and early 1980's when OV-98 - OV-104
were built.

>Anyway, there seems to be some proof that multi-year funding can help save
>money over time -- even if the congressmen don't like it.

This is very often the case in defense aerospace programs such as aircraft
production.  Long lead-time materials (e.g. large supplies of titanium) tend to
be much cheaper if you order in quantity; but if the contractor is only
guaranteed funding for X items, then they can only order Y amount of the
material.  If congress funds another batch of X items two years later, then
another Y batch of the material is bought.  The price of the two small batches
is much higher than the price of one equivalent large batch.  I'm not sure
what typical ratios are, but I get the feeling that it's on the order of 2:1.

Just another instance of the observation that a 16 ounce box of Cherrios costs
more that half what a 32 ounce box costs.
						-- Tom

    Mr. Moderator, feel free to move this as appropriate ... I couldn't
    find an appropriate note (though I looked through keywords like "news"
    and "shuttle" along with titles with those words as well as "future").
    
    This is regarding a blurb I heard on the radio this morning (July 25,
    1991).  To paraphrase:
    
    "With yesterday's delay of the launch of the space shuttle Atlantis,
    President Bush is now going to recommend that NASA abandon manned
    launch vehicle development in favor of unmanned launch capabilities."
    
    "According to Mr. Bush, yesterday's delay was 'the last straw'."
    
    I was upset at this statement because of the obvious implications if
    Uncle George is serious about this (assuming the report had even a
    shred of truth in it).  Anybody hear this, or have something more
    concrete than my "heard it on the way to work" synopsis?
    
    ...Roger...

  The Globe also had a small piece on how NASA would emphasize unmanned
launchers, but they seemed to be talking about launching satellites and down
playing the Shuttle as a launching system. Of course, that's old news. I guess
the real question is whether they are planning to move away from development of
the space plane. 

  I think the bottom line here is that Bush doesn't really know or care much
about what's going on with the space program. I wouldn't take anything he
says too seriously. In fact, yesterday a reporter asked him what he was going
to do about Iraq's deadline for giving information on their nuclear development
and he had to ask his security adviser what they were talking about.

  If he's not up on that, I doubt he's up on the space program. Remember, this
guy is the protege of the Great Slumbering Communicator.

  George

    Re: last couple
    
    Another case of media ignorance.  What has happened is that the
    National Space Council has approved the National Space Launch Strategy,
    which consists of the following:
    
    1)	New Launch System, a series of medium and heavy lift boosters
    
    2)	SDI single stage to orbit (SSTO) launcher, which can operate manned
    	or unmanned
    
    3)	X-30 NASP research vehicle
    
    4)	Maintenance of current four orbiter STS fleet.  No new orbiters
        to be procured unless we lose one or aging takes a heavier toll
        than anticipated.
    
    It doesn't mean the end of manned spaceflight.  The shuttle will
    provide that capability throughout the 1990s, and with the reduced
    flight rate, will suffice until a new dedicated manned system (SSTO,
    NASP follow-on, or something simple like PLS) is developed.  Of course,
    there will have to be a follow on program, but that may be happening in
    a de facto manner already, with NASP, SSTO, and PLS/ACRV for Freedom. 
    In fact, the SSTO, which is man-rateable, will make its first flight
    before NASP (albeit unmanned) if the funding profile holds up.  What
    the press did is take a programmatic decision (no funding for a fifth
    shuttle) and blow it up into "Bush says no more manned flights."

    Yup, the media do a great job as long as they stay away from subjects
    you (the reader) may know something about.
    
    The reply in .7 sums it up well. The only thing I would add is that the
    HL-20 (ACRV) seems to be gaining support as a personnel launch system,
    in conjunction with a man-rated Titan 4.
    
    The press also had some drivel about missiles being retired because of
    START that could be used for launch vehicles (this last item may have
    been a Quayle-ism).
    
    gary

    Re: last, retired missiles as launchers

    Drivel is right.  I believe the START treaty, like the INF treaty
    before it, requires that missiles made redundant under the treaty be
    scrapped.  BTW, They have more birds in this category (150 SS-18s, for
    starters) than We do.

Article: 68016
From: [email protected] (Paul Dietz)
Newsgroups: sci.space
Subject: A Blast from the Past
Date: 27 Jul 93 00:43:50 GMT
Organization: University of Rochester
 
The following article is apropos to some of the recent
discussions on this list...
 
------------------------------
"Shuttles -- What Price Elegance?"
[Robert C. Truax, Aeronautics/Astronautics, June 1970, pages 22-23.]
 
After years of debate, the reusable orbital shuttle appears to be
headed for full project status.  It may be unseeming for the true
believers, who have been arguing the case for reusability over the
years, to begin haggling over the details so soon, but 'twas ever thus. 
 
My concern is that the approach selected will include many unnecessary
frills that will run up the cost and extend the development time to
the point where the program becomes another Dynasoar or MOL.  All too
many government projects go this route.  American industry can perform
technological prodigies, as we have witnessed in the Apollo and
ballistic-missile programs.  The national resolve must be firm,
however, if success of such projects is to be assured.  Long,
difficult technical developments are seldom successful if the
justification is not crystal clear; and, let's face it, the
justification for the reusable orbital shuttle is *not* crystal clear.
Although a favorable administrative decision appears at hand, the
subject is still controversial among the experts.  It is therefore
vital to the success of the project that its costs and duration be
minimized.  The mood of the country will not support another
engineering "tour de force". 
 
With the above considerations in mind, I would like to point out once
more that, with the proper approach, development of a reusable orbital
transport need not be particularly difficult, expensive or
time-consuming ("Thousand Tons to Orbit", R. C. Truax, Astronautics,
January 1963.  "The Pressure-fed Liquid, Dark Horse of the Space
Race," R. C. Truax, IAF Convention 1967.) 
 
It is necessary, however, to keep the primary objectives in the
forefront and ruthlessly exclude features technically difficult but
contributing only marginally to the central purpose. 
 
The features which I consider in the category of peripheral frills,
but which present vast difficulties, include land touchdown and
booster flyback.  These features, unfortunately, are near and dear to
many proponents of reusable vehicles.  They make the "aero" part of
the aerospace industry feel needed.  They even have an appeal to the
non-technically minded.  But they make about as much sense as
requiring airplanes to be able to land at railroad stations. 
 
For the moment assume that the reusable orbital transport requires at
least two stages, and talk about the upper stage(s) first.  We already
have a reusable spacecraft, maybe two.  With minor design changes,
both the Gemini and Apollo spacecraft are reusable.  There is no
approach to returning a craft to Earth from orbit that is simpler,
which costs less payload, or, I submit, which is either quicker or
less costly to develop or to operate that the low-L/D,
parachute-landed spacecraft using water touchdown. 
 
The present type of heat shield probably must be replaced each flight.
An intrinsically reusable or a less-sophisticated expendable shield
might prove more economic for repeated use.  But I can see no valid
argument for abandoning the essentially ballistic re-entry with
parachute touchdown in water. 
 
Let us examine what we pay for winged or even lifting-body re-entry,
and what we reeive in exchange.
 
In the re-entry phase, we trade off high heating rates and receive
longer heating times and *greater* total heat-input.  The net effect
is loss of payload.  We gain lower re-entry accelerations.  If we have
as our chief aim shuttling little old ladies (or possibly a president
with a weak heart) to and from Earth orbit, I would agree that lower
"G" is a significant advantage.  As long as the crew and passengers
are even moderately healthy individuals, at least one step removed
from the wheelchair, the reduced acceleration cannot be [presented] as
a significant advantage.
 
The second "advantage" touted for the high L/D re-entry is
"footprint."  A large footprint carries the capability for a wider
selection of landing point for a given deorbiting condition.  However,
any landing point within the maximum latitude excursion of the
orbiting craft can also be selected by waiting a bit longer and
deorbiting at the proper time.  The Apollo spacecraft has built into
it all of the lift capability required to compensate for deorbiting
errors and to permit reasonably short orbital "holding times."  How
much are we willing to pay for a minor gain in scheduling convenience?
 
Expansion of landing opportunities in emergencies cannot be cited as
an advantage of high-lift re-entry.  It may be a necessary adjunct,
but a lifting-body craft probably cannot be safely ditched in the
ocean, nor can it be landed on rought terrain.  The ballistic vehicle
with aprachute can do both, and in substantially any weather.  Its
touchdown on land may damage the craft some, but the probability for
survival of the occupants is very high.  The crew of a winged re-entry
vehicle, on the other hand, coming in for an emergency landing might
learn to their grief that three quarters of the surface of the Earth
is water!
 
Use of special lifting bodies cannot be justified on the basis of
touchdown accuracy.  Only ultra-conservatism and concern for our
astronauts' safety prevents us from recovering one mile off Cocoa
Beach.  Nor is it necessary to have half the U.S. Navy standing by.  A
helicopter or pickup boat could have the spacecraft and crew back at
the launch site within minutes.  Does it matter whether they ride in a
boat or on wheels?  As a matter of fact, barring the construction of
expensive new runways and other facilities, the land-landing
spacecraft will wind up further from its launch site than one the
lands on water!
 
Most of these results about the spacecraft (i.e., the payload module)
apply also to the upper propulsive stage.  Minimizing the exposed
area generally minimizes the problem of heat protection.  The arguments
for winged re-entry are even less valid for the ascent propulsion
stage unless it is permanently attached to the payload module or
separately manned.
 
The penalties for doing the latter are serious.  Perhaps the most
powerful argument for separating the two modules is that one does not
need to return a cargo enclosure.  Indeed, it can be quickly shown
that it is uneconomical to do so.  Mixed passenger and cargo flights
should be the exception, rather than the rule.  Propellants, in
particular, should be transported to orbit in a throwaway container.
We should never try to maximize the amount of empty container
that must be brought back through the "thermal thicket."  If,
indeed, it proves economical to return expended upper stages,
they should be left to make the journey alone -- started on their
way, perhaps, by a space "switch engine" which gives them proper
orientation and impulse, and then returns to the space station.
 
I have saved my comments on the first stage until last because it is
here I feel we can make our greatest mistake.  A winged, flyback
booster could be a money sponge of unparalleled capacity.  It is,
unfortunately, the kind of technological challenge that engineers
cherish and which they may be expected to recommend with unstinted
enthusiasm.  It is also the avenue to participation and profit by an
airplane-oriented industry.  Even if the many-fold problems we create
by such a requirement can indeed be solved by vast injections of
cash, the payoff, I am convinced, is completely trivial.
 
Let us examine the two features separately.  Take flyback first.  Why
fly?  Well, flying saves time -- but it also costs money, particularly
if we are trying to fly back a huge booster, for we have to take its
transport plane into space with us first.  Yet that is essentially
what we propose to do.  I will not belabor the point that making a
space booster that is also a hypersonic airplane is a formidable
problem.  Even the staunchest proponents admit that.
 
Instead, let us see what would be gained if we indeed had such a beast.
First, we would gain time.  The return from a few hundred miles down range
would be in a matter of minutes.  Return by tug or retrieval vessel would
require perhaps 24 hr.  When launch intervals approach this figure,
the saving in time would permit a reduction in vehicle inventory.
However, since the cost ratio between simple ballistic and flyback
booster must be at least 10 to 1, the breakeven launch interval would
be several per day.  I am sure that such high utilization rates go
far beyond the lifetime of this first-generation reusable booster.
The savings in time, then, is not a valid argument for flyback.
 
How about land touchdown?  Like an airplane, I mean.  The usual
argument is that airplane turnaround costs are a few thousand dollars
at most (i.e., Boeing 707 in commercial service) whereas expendable
ballistic boosters cost millions just to check out and launch.
Certainly (the argument goes) a booster that has splashed in salt
water and been towed hundreds of miles would have to be completely
rebuilt at heaven knows what cost!  A reusable booster that looks
like an airplane, flies like an airplane, and, above all, lands
like an airplane will probably have turnaround costs approaching
that of an airplane.  I say nonsense!  This opinion simply reflects
wishful thinking and "gut feel".  So is the pessimistic appraisal
of the effect of water landing on refurbishment cost.
 
As I have pointed out on a number of occasions, the structural
fraction of a winged flyback booster is about on a par with a
scaled-up Aerobee.  A simple, rugged pressure-fed booster would
perform as well as the ultra-complex flyback VTOHL (or HTOHL).  The
pressure-fed booster could be recovered by means of a relatively small
inflatable drag-device.  Studies have shown that water-entry
velocities up to several hundred feet per second could be sustained
without damage.
 
Naturally, a water-landing booster must be designed to exclude sea
water from any electronics or delicate machinery; but the unmanned,
simple system I have suggested before involves precious little
such claptrap.  The problems are not essentially different from those
encountered in excluding sea water from ships, submarines or seaplanes,
all of which operate immersed in the ocean for much longer periods
than a reusable booster.  Quite similar rockets (liquid JATO of
WW II) have been dropped in the ocean and reused many times without
*any* refurbishment, other than reservicing with propellants.  An
experiment with a modified Aerobee (Seabee) showed a refurbishment
factor of only 7% on the first try!
 
No, far from having a higher turnaround cost than the winged flyback
booster, the pressure-fed rocket, utilizing a ballistic path, pure
drag retardation, and vertical, water touchdown with tug return would
have a much lower turnaround cost.  It would, for the simple reason
that there is so much less to refurbish!
 
There is only one advantage to the horizontal-landing flyback
booster that I would freely acknowledge.  The late, redoubtable Nick
Golovin termed water landing "inelegant."  I would agree, but how much
are we willing to pay for elegance?
 
------------------------------
 
	Paul F. Dietz
	[email protected]
 
	"Absolute stupidity of the worst sort"
		-- Freeman Dyson commenting on the space shuttle