Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V15_4/V15NO463.TXT

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Date: Fri, 27 Nov 92 05:03:24
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #463
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Space Digest                Fri, 27 Nov 92       Volume 15 : Issue 463

Today's Topics:
                         Dante on "Nightline"
                         DC and Fallen Angels
                         Environmental group
                           Hubble's mirror
            hypergolics (was Re: Pumpless Liquid Rocket?)
             Kuiper belt planetesimals and Planet X claim
                         Moon Capture Theory
                       Pumpless Liquid Rocket?
                     Shuttle replacement (9 msgs)
                              Simplicity
                            Solar sailing
                    What comes after DC-1 (3 msgs)

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----------------------------------------------------------------------

Date: Thu, 26 Nov 92 14:18:38 EST
From: John Roberts <[e-mail]>
Subject: Dante on "Nightline"

-From: [e-mail] (John Thompson Reynolds)
-Subject: Re: Dante on "Nightline"
-Date: 25 Nov 92 14:17:01 GMT
-Organization: HaL Computer Systems, Inc.

-Just out of curiosity, is there any valid Science being done by this NASA
-"mission" to Antartica,

Yes.

-or is this just showboating to get some network
-coverage?

No.

-Assuming that science is in fact being done, what does it have
-to do with Aeronautics and Space?

The *science*? Not a whole lot. (I think there is some ground-based work
going on in Antarctica to evaluate the ozone hole.)

-Why is NASA getting involved in
-oceanography?

The main objective from NASA's viewpoint is to test rover design and
techniques used in teleoperation, under conditions that in some ways
approximate those of other planetary bodies and conditions in space.
The arroyos near JPL and the slag heaps near Pittsburgh also serve as
approximations, but but it's helpful to have another. The value of the
underwater craft appears to be mainly in its operator feedback mechanisms,
though perhaps the approximation of "zero G" could be useful too.

The science obtained is a bonus - apparently sufficiently valuable that they
didn't just cook up big refrigerated chambers in the US (though artificial
environments are not as effective for finding unforeseen problems). Also,
it should be noted that having rovers and teleoperated devices that can
operate under adverse *earth* conditions can be useful in itself. (After
the Chernobyl meltdown, according to the NOVA episode, the expensive
western-supplied robots broke down because of the intense radiation - they
finally found a remote-controlled toy truck that could do the job, with
a television camera strapped on the top.)

-I can see them supporting other organizations such as NOA,
-but I can't see why they would be "stealing the limelight".

Do you think there's an official NASA oceanographer who's going to be the
only person allowed to look at the data? I'd guess that some people at
CMU and elsewhere would be rather surprised to hear that.

I'd say that if NASA can build up its involvement in robots and teleoperation
systems, it will be of considerable long-term benefit to the space program.

John Roberts
[e-mail]

------------------------------

Date: Thu, 26 Nov 1992 18:15:54 GMT
From: Henry Spencer <[e-mail]>
Subject: DC and Fallen Angels
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Hugh Emberson) writes:
>The zeroth stage would be like a big SSTO with fuel tanks, lots of
>engines and guidance.  It would sit under the SSTO and act like a
>first stage booster for the SSTO.  When it was nearly out of fuel it
>would seperate, fly back down and land -- ready for reuse.  The book
>says that with this the SSTO could reach GEO.
>
>Has McDD thought of this?

Undoubtedly; this is just a two-stage (rather than single-stage) launcher.
It does re-introduce assorted problems like first-stage recovery and the
need for re-stacking, though.  The whole point of SSTO is getting away
from things like that.

>Did McDD get their ideas from Hudson?

Probably not directly.  Hudson is not the only one who's been pushing
concepts like this, although he's been more visible than others.  A much
better candidate for influence on McDD is Max Hunter (who, among other
things, used to be one of their senior people -- he designed Thor, the
missile that eventually became Delta).  Hunter was definitely involved
in the campaign to get SDIO involved in funding SSTO development.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

------------------------------

Date: Thu, 26 Nov 1992 18:18:48 GMT
From: Henry Spencer <[e-mail]>
Subject: Environmental group
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (John Roberts) writes:
>NASA and its contractors have been testing SRMs for a long time. I had
>presumed that at least some of that was done at Stennis.

Nope.  The SRM tests are entirely done at Thiokol facilities in Utah,
I believe.  For some strange reason, those aren't available to non-Thiokol
projects. :-)

>(They're not planning to test *beryllium* fuel, are they?)

No, the ASRMs have nothing so exotic.  But Stennis tests have been entirely
liquid-fuel rockets, as far as I know.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

------------------------------

Date: Thu, 26 Nov 1992 18:00:04 GMT
From: Henry Spencer <[e-mail]>
Subject: Hubble's mirror
Newsgroups: sci.astro,sci.space

In article <[e-mail]> [e-mail] (David M. Palmer) writes:
>How do you do an end-to-end imaging test?  The depth of field of
>an instrument with Hubble's aperture is such that a point source
>must be thousands of kilometers away in order to be in focus.

I'm not an optics guru... but the test was considered feasible, if costly
and somewhat risky.  My guess would be a bit of optics to move a real
source out to a virtual infinity, as is done in head-up displays.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

------------------------------

Date: Thu, 26 Nov 1992 17:43:34 GMT
From: Henry Spencer <[e-mail]>
Subject: hypergolics (was Re: Pumpless Liquid Rocket?)
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Charles R. Martin) writes:
>   If you're willing to settle for a hybrid liquid/solid combination, water
>   and aluminum foil work once you get them started...
>
>What would it take to light it off?  Would thermite be sufficient?

I'd imagine so; the thought of thermite not being able to ignite something
that is ignitable doesn't seem very plausible... :-)

Just in case I didn't make it clear enough the first time, though:  be
warned that even a small rocket engine is dangerous.  When thinking about
size and accident potential, bear in mind that a typical military hand
grenade contains less than 100 grams of explosive... an explosive less
potent than a lot of rocket-fuel combinations.

Aluminum-water explosions have blown roofs off armored test cells.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

------------------------------

Date: Thu, 26 Nov 1992 17:55:49 GMT
From: Henry Spencer <[e-mail]>
Subject: Kuiper belt planetesimals and Planet X claim
Newsgroups: sci.astro,sci.space

In article <[e-mail]> [e-mail] (Andrew C Goldish) writes:
>  Now that objects have been sighted that could possibly prove the existence
>of the Kuiper belt, is it possible that the combined gravity of all the
>planetesimals (at least those near Neptune) is enough to perturb Neptune's
>orbit? ...

Doubtful.  I think we'd have seen more of them if there had been that much
mass out there.

More fundamentally, according to the spacecraft-navigation people at JPL,
if you use only 20th-century data, *there are no unexplained perturbations*
in Neptune's orbit.  The situation doesn't look quite so good if you use
older data (some of which should be quite reliable), but the 20th-century
fit is good enough that people have been driven to mechanisms like highly
elliptical, highly inclined orbits to try to get Planet X out of the way
in recent times.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

------------------------------

Date: 25 Nov 92 03:21:41 GMT
From: Josh 'K' Hopkins <[e-mail]>
Subject: Moon Capture Theory
Newsgroups: sci.space

roelle@uars_mag.jhuapl.edu (Curtis Roelle) writes:

>[e-mail] (James Davis Nicoll) writes:

>>>>I seem to remember some theory a while back that the moon was actually
>>>>*captured* by Earth at some stage (I think it was about 800 million
>>>>years ago), which also has corollaries in some of the very early
>>>>human legends.

>>    I  find  it *very* difficult  to believe  that events  800
>>million  years ago would  have corollaries  in  the myths of  a species
>>4  orders of magnitude less old, except  perhaps by co-incidence.

>Perhaps these corollaries originated from an intelligent species of lizard
>wiped out without a single trace by the Mother of all Extinction Events.

First of all, 800 million years BCE puts the event well before almost any type
of life you can imagine was intelligent.  Secondly, even if the dinosurs did
know about the Moon, there's no way they could pass this on to humans who
evolved roughly 60 million years later.
--
Josh Hopkins                                          [e-mail]

    "Why put off 'til tomorrow what you're never going to do anyway?"

------------------------------

Date: Thu, 26 Nov 1992 17:51:08 GMT
From: Henry Spencer <[e-mail]>
Subject: Pumpless Liquid Rocket?
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Markus Pristovsek) writes:
>such a cheap pumpless rocket was build a time ago, It was planned, to
>connect 100s of tubes, each with H2NO3 and a hydrocarbon like propan or
>something like this. It was a private german/french and algeric enterprise.

If you're thinking of OTRAG, that design was pressure-fed, which isn't
quite what's being proposed here.  Pressure-fed rockets are nothing new,
although they're seldom built in large sizes.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

------------------------------

Date: Thu, 26 Nov 92 13:08:54 EST
From: John Roberts <[e-mail]>
Subject: Shuttle replacement

-From: [e-mail] (Henry Spencer)
-Subject: Re: Shuttle replacement
-Date: 24 Nov 92 21:50:52 GMT
-Organization: U of Toronto Zoology

-More precisely, the shuttle has never had any provision for escape during
-boost.  Both its escape systems -- the ejection seats carried for the first
-four flights, and the escape pole carried now -- require gliding flight at
-relatively low altitude.  (Technically the seats could have been used during
-boost, but the probability of survival approached zero.)  Both were meant
-as alternatives to a (probably unsurvivable) ditching or belly landing,
-not for instant escape during powered flight.

During the first Shuttle flight, Launch Control informed the crew at a certain
point during the boost phase that they had passed the maximum altitude at
which the ejection seats could be used. (Not to claim that using them earlier

would have been effective.)

->>             I cant remember wether apollo used a escape rocket
->>or the SM engines,
->It had an escape rocket.

-Actually, it used either one, depending on timing.  The escape rocket
-was jettisoned after it was no longer needed.

Didn't Apollo eventually quit using escape rockets?

John Roberts
[e-mail]

------------------------------

Date: Wed, 25 Nov 1992 03:50:54 GMT
From: Josh 'K' Hopkins <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

[e-mail] (Gary Coffman) writes:

(Henry Spencer) writes:
(Allen W. Sherzer) writes:
>>>>the idea of a powered descent and vertical
>>>>landing gives me the willies...
>>>
>>>Much safer than airplanes for most people. A DC crash will only affect the
>>>Spaceport. When aircraft crash they tend to kill people on the ground.
>>
>>And as any Harrier pilot will tell you, a vertical powered landing is
>>safer than a horizontal powered landing.  And either one is *much* safer
>>than a Shuttle-style horizontal landing *without* power.

>As any glider pilot will tell you, gliders don't burn on impact. Nor
>do they pinwheel across the sky when a thrust diverter fails.

The only thing a shuttle landing has in common with a standard glider landing
is that neither uses engines.  I've heard astronauts describe the shuttle
while it's landing as performing like a greased brick.  If I recall correctly,
a 747 with engines off can glide better than a shuttle.  Besides, crash landing
the shuttle would not just cause a piddly little mess.  The shuttle weighs
much more than a glider, lands faster than a glider and happens to carry fuel
anyway.
A vertical powered descent probably is safer than other methods.  Of course,
this doesn't mean that the safety issues should be ignored.
--
Josh Hopkins                                          [e-mail]

    "Why put off 'til tomorrow what you're never going to do anyway?"

------------------------------

Date: Thu, 26 Nov 1992 17:31:51 GMT
From: Henry Spencer <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space.shuttle,sci.space

In article <[e-mail]> [e-mail] (Gregory N. Bond) writes:
>What are the limits on scaling up something like DC-Y?  My intuitive
>guess would be that scaling up should be _easier_...

Generally correct.  There's no obvious upper limit.  People have proposed
some really huge SSTO designs in the past; most things get easier at large
size.  (You can theoretically build a *solid-fuel* SSTO if you make it
big enough, I'm told.  Although why you'd want to...)

One obvious nuisance is going to be engine development, though.  You can go
only so far with clustering; sooner or later you need bigger engines.  Mind
you, the ones we've got (or can reconstruct, e.g. the F-1) should suffice
for some pretty huge SSTOs...
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

------------------------------

Date: Thu, 26 Nov 1992 17:35:12 GMT
From: Henry Spencer <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Steinn Sigurdsson) writes:
>   You are referring to the two Palpa communication satellites. It was about
>   all the Shuttle could do and it cost the taxpayers hundreds of millions
>   in launch subsidies.
>
>   We spent half a billion $$ to recover $75 million worth of satellites...
>
>Come on Allen, you can't charge the whole cost of the flight to
>the rescue, this has been hashed out a dozen times...

It's been hashed out a dozen times for the Intelsat repair, which was added
on to an existing test flight.  The Palapa/Westar retrieval mission did
almost nothing else that I recall; there you really do have to charge most
of the mission against the retrieval (or you would, were it an operational
mission -- you can justify a few as experiments).  NASA doesn't test-fly
new orbiters all that often...
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

------------------------------

Date: Thu, 26 Nov 1992 17:48:57 GMT
From: Henry Spencer <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Allen W. Sherzer) writes:
>>   Not exactly, Allen. The Solar Max repair mission came pretty close to
>>   this in 1984. If the STS-41C crew had been unable to repair Max, they
>>   would have brought it home.
>
>I'm not sure but I doubt they could have returned Solar Max that mission.
>I don't see how they could have put both LDEF and the fixtures for Solar
>Max in the payload bay.

The fixtures needed for bringing Solar Max back were exactly the ones
needed to anchor it for repairs; no problem there.  (I think the fit in
the payload bay *was* a wee big snug until LDEF was removed.)  It would
have required jettisoning the solar arrays, though.

However, I recall one of the principal investigators for Solar Max saying
that everyone on his team was hoping and praying it didn't happen, because
the most likely result was that Solar Max would end up in the Smithsonian.
There was no money, and no likelihood of money, for further repair efforts
or a relaunch.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

------------------------------

Date: 25 Nov 92 15:17:07 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Dan Vento) writes:

>No I'm not referring to Get Away Specials. I mean all of the Middeck,
>Hitchiker, MSL, MPESS, SMIDEX, Spacelab Glovebox, etc. experiments...

Whatever. The point is that they take up a very small amount of space
and we wouldn't need Shuttle to transport them to and from an orbital
facility.

An orbiting permanent space lab would provide several times the
utilization of Shuttle spacelab which flies only once a year.

>Much basic engineering needs to be rethought before you try to apply it to
>microgravity.

Exactly. Doing this requires LOTS of flights which we don't get with
Shuttle.

>An ISF type facility would be useful for some things, but I am skeptical
>that there would be sufficient commercial interest to develope enough
>hardware to fill it.

Well if you can fill up Shuttle and Spacelab this shouldn't be any
problem.

  Allen
--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | "A great man is one who does nothing but leaves        |
|  [e-mail]     |  nothing undone"                                       |
+----------------------150 DAYS TO FIRST FLIGHT OF DCX----------------------+

------------------------------

Date: Thu, 26 Nov 1992 16:06:14 GMT
From: Gary Coffman <ke4zv!gary>
Subject: Shuttle replacement
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Allen W. Sherzer) writes:
>In article <[e-mail]> [e-mail] (Gary Coffman) writes:
>
>>Goodbye Disney World. A flying bomb with no destruct sequence isn't
>>acceptable.
>
>A bit less zenophobia please! what the hell do you think an airliner is?

Something with *wings* on it.

Gary

------------------------------

Date: Thu, 26 Nov 1992 16:18:42 GMT
From: Gary Coffman <ke4zv!gary>
Subject: Shuttle replacement
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>In article <[e-mail]> [e-mail] (Gary Coffman) writes:
>>>A range safety officer can blow up a Shuttle, not so with Delta Clipper.
>>
>>Goodbye Disney World. A flying bomb with no destruct sequence isn't
>>acceptable.
>
>Have you told the FAA about this?  They've certified many types of airliners
>for flight with very full tanks and no destruct systems.

The proposed DC-1 is nothing like an airliner, airliners have wings and
a limited gliding ability. Nor is the proposed DC-1 anything like a
helicopter which can autorotate if there is a power failure. Nor do
either of these systems require high performance rocket fuel. On a
related note, you said the proposed DC-1 would land on nearly empty
tanks. Does that mean it can't abort an approach and try again?
Licensable aircraft *must* be able to do this. Flying on fumes is
an FAA violation.

Gary

------------------------------

Date: Thu, 26 Nov 1992 16:47:50 GMT
From: Gary Coffman <ke4zv!gary>
Subject: Shuttle replacement
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Allen W. Sherzer) writes:
>Both configurations are fairly close in terms of weight especially considering
>that Titan today can launch almost anything. How about this comparison:
>
>Shuttle cost: ~10,000 per pound
>Titan cost:   ~ 3,000 per pound
>
>Now if YOU where paying the bills (and as a taxpayer, you are) which do
>you consider the better buy?

The one where you can send a mission specialist, or three, out to kick
the damn payload when it doesn't deploy properly. Do we really give a
damn what the launch costs if the payload doesn't work after we get it
on orbit?

Gary

------------------------------

Date: Thu, 26 Nov 92 16:39:51 EST
From: John Roberts <[e-mail]>
Subject: Simplicity

-From: [e-mail] (Allen W. Sherzer)
-Subject: Re: Simplicity
-Date: 25 Nov 92 12:44:14 GMT

-In article <[e-mail]> [e-mail] (John Roberts) writes:
->Reliability is dependent on many factors, of which simplicity is only
->one. If you took all the redundant components out of the Shuttle, it
->would certainly be simpler, but it would probably be *less* reliable.

-Simple designs can have redundancy. DC is a simple design; all it is
-is tanks, fuel, avionics, engines, and a payload. Yet it has enough
-redundancy to provide for intact abort throughout its envelope.

Good point. Another important factor is the extent to which a design
"pushes the envelope" of the available technology. The SSMEs push the
envelope pretty hard, which is why they have to be serviced so extensively
after each use. DC doesn't do that as far as the engines are concerned, but
Goldin has expressed the opinion that thermal control is at least as much of a
challenge as for NASP, perhaps more so. Any comments?

-Shuttle has redundancy but no simplicity. It has more and more complex
-interfaces which reduces reliability. Reliable systems tend to be ones
-where a single person can pretty much understand the operation of the
-entire machine.

"Understandability" may be a more important factor than simplicity as such -
if a system is understandable, it's easier to spot design errors. But that's
not the final word on reliability - the human body is (in general) much more
reliable than any launcher, but also vastly more complex and difficult to
understand.

John Roberts
[e-mail]

------------------------------

Date: Thu, 26 Nov 92 14:44:28 EST
From: John Roberts <[e-mail]>
Subject: Solar sailing

-From: [e-mail] (Colin Tinto)
-Subject: Re: Solar sailing
-Date: 25 Nov 92 12:35:13 GMT
-Sender: [e-mail] (USENET News System)
-Organization: Spider Systems Limited, Edinburgh, UK

-In article <[e-mail]> [e-mail] (John Roberts) writes:
->Bonus question (meaning I don't have any idea how to work out the math):
->  In designing sails for sailboats, it usually works out that the optimum
->  sail is a nonplanar piece of fabric, mounted with some slack so that the
->  wind inflates it to a particular curved shape. Is that also the case
->  for a solar sail, when one wants to maximize tangential thrust per unit of
->  sail area? (If so, the mechanism would be multiple reflections.)

-I'm no expert on this (Maths, Space, Sails....) but I always thought sailboats
-worked partly on differences in air pressure.

-The sail having differing pressure on either side - sucking the boat along.

At the molecular level, it's not a matter of "sucking" - it's a matter of
relative pressures ("pushing").

"Air pressure" is a way of referring to the statistical interaction of
trillions of trillions of air molecules. What I was referring to is
mechanical analogy - this is an old tried-and-true technique taught in
Junior-level engineering classes. (For instance, an electrical circuit
can be modeled by either a translational or a rotational mechanical
system - if you apply the correct conversion factors, the systems are
essentially equivalent in their mathematical description.) There are
several ways in which light can be thought of as a pressurized gas -
the main difference is that the individual photons have little or no
interaction with one another. So it *could* be that a curved sail (which
causes some of the photons to reflect multiple times) would give greater
transverse thrust than an equavalent flat sail, and it could be that
the available photon pressure of sunlight would be adequate to "inflate"
the slack sail and hold it in the desired shape. I was wondering if
anybody has studied this already.

This is of considerable interest because all of the proposed large solar
sails *are* somewhat curved - it's very difficult to keep such a large and
flimsy structure flat. One factor I'd be interested in is how much of a torque
a curved sail tends to generate.

-Now unless there is something like light pressure ???

Power / c, for a directed beam.

John Roberts
[e-mail]

------------------------------

Date: Thu, 26 Nov 1992 16:54:36 GMT
From: "Herity D." <[e-mail]>
Subject: What comes after DC-1
Newsgroups: sci.space

[e-mail] (Henry Spencer) writes:

>The only real question is whether its thermal protection is adequate for
>a lunar reentry.

This should be ok if it returns to a decaying orbit, instead of trying to
reenter in one go. This needn't present any greater thermal or mechanical
problems than reentry from LEO.
--
================================================================================
| Dominic Herity,  dherity@.cs.tcd.ie,                      | Something clever |
| Computer Science Dept, Trinity College, Dublin 2, Ireland.| coming soon to a |
| Tel : [phone] ext 1720 Fax : [phone]        |signature near you|

------------------------------

Date: Thu, 26 Nov 1992 16:35:41 GMT
From: Gary Coffman <ke4zv!gary>
Subject: What comes after DC-1
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Allen W. Sherzer) writes:
>In article <deanr.722718879@sco> [e-mail] (Dean Reece) writes:
>
>>How hard (how many mods) would need to be made to re-fuel a DC-1 on
>>orbit?  Assume the fuel is there for starters.
>
>The Russians refuel on orbit so I assume not much.

The Russians don't refuel cryo systems on orbit. Big difference.

>>Could we strap on SRB's to the DC-1 to increase payload (bad joke...
>>forget I said it :-)
>
>Well, people have proposed it (not SRB's but strap ons). It defeats
>most of the purpose and adds cost but it might be worth while if DC1
>turns out to be more marginal than expected.

We *know* from experience that weight always increases and performance
always decreases on the way from the drawing board to the launching
pad. SRBs may be the only way the proposed DC-1 ever gets to orbit.
And if that turns out to be the case, as you note, the correct reaction
would be "why bother" we already have a larger, more capable, system
that works that way.

>>I realise that its a bit early to answer these questions with any
>>certainty, but any serious thoughts on these questions would be
>>appreciated.
>
>Remember that DC1 isnt' on the drawing boards yet. Nobody can say for
>sure what the requirements will be.

So it's not even a *paper* airplane.

Note that I've taken on the self-appointed task of throwing cold water
on this system. I hope that it works as predicted, but I've seen enough
wild promises to be doubtful. Everything about the proposed DC-1 requires
operation on the thinnest of margins. Any system pushing that close to
the limits *all* the time is likely to be finicky and dangerous if it
works at all. That's why SSTO has never been seriously considered before.

Gary

------------------------------

Date: Thu, 26 Nov 1992 16:54:43 GMT
From: Gary Coffman <ke4zv!gary>
Subject: What comes after DC-1
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Hugh Emberson) writes:
>
>The zeroth stage would be like a big SSTO with fuel tanks, lots of
>engines and guidance.  It would sit under the SSTO and act like a
>first stage booster for the SSTO.  When it was nearly out of fuel it
>would seperate, fly back down and land -- ready for reuse.  The book
>says that with this the SSTO could reach GEO.
>
>Has McDD thought of this?

Von Braun certainly thought of this. A flyback booster was part of
the original Shuttle configuration. It had *wings* too.

Gary

------------------------------

End of Space Digest Volume 15 : Issue 463
------------------------------