Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V15_4/V15NO468.TXT

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Date: Sun, 29 Nov 92 05:00:05
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #468
To: Space Digest Readers
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Space Digest                Sun, 29 Nov 92       Volume 15 : Issue 468

Today's Topics:
        "Lecture by Tether Scientist involved in TSS-1 (long)"
  Environmental group to sue NASA to stop rocket motor fuel testing
                            escape systems
                  Evil wicked flying bombs! (2 msgs)
                   Mars Observer Update - 11/13/92
                             Pop in space
                     Shuttle replacement (6 msgs)
Spacewalk added to shuttle flight, more expected [Release 92-210] (Forwarded)
                    Want info: sharp gun/launcher
                        What comes after DC-1

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

Date: 28 Nov 92 17:53:47 GMT
From: Tom A Baker <[e-mail]>
Subject: "Lecture by Tether Scientist involved in TSS-1 (long)"
Newsgroups: sci.space

[The following article appeared in the November 1992 issue of SPACEVIEWS, the
newsletter of the Boston Chapter of the National Space Society.  IT IS
AVAILABLE VIA EMAIL; see the end of this message for information. - tb]

Copyright (C) 1992 Roxanne Warniers

October Lecture Summary

by Roxanne R. Warniers

October's lecture was given by Dr. Gordon Gullahorn of the
Harvard-Smithsonian Center for Astrophysics. His colleague, Dr.
Robert Estes also attended. Dr. Gullahorn discussed the first
mission of the Tethered Satellite System (TSS-1) that was the
major payload of the August Shuttle flight. The main science
goal of this mission was to "characterize the electrodynamic
behavior of the satellite-tether-orbiter system" [NASA brochure].

We all know the incredible frustration of the mission when the
deployed satellite stopped after the tether had only uncoiled
256 meters. (The satellite was to extend 20 kilometers.) In the
final analysis, an over-cautious engineer was responsible for
the problem. While mounting the level-wind assembly, an engineer
decided an additional bolt should be added to better secure the
assembly. This extra bolt ultimately prevented the tether from
unwinding by blocking the guide that slides back and forth
across the reel to unwind/wind the tether.

Dr. Gullahorn passed around a sample of the tether which looked
remarkably like old-fashioned clothesline. Manufactured by
Cortland Cable Company (New York), the center copper wire (the
electrical conductor) is insulated with Teflon, covered with
braided Kevlar and an outer jacket of Nomex.

The satellite at the end of the tether was developed by Italy's
Agenzia Spaziale Italiana (ASI, the Italian Space Agency).

Dr. Gullahorn was the Principal Investigator for experiment
titled "Investigation and Measurement of Dynamic Noise in the
TSS." His experiment focused on the oscillations from a
long-tethered object in space. Although the major
characteristics of these oscillations is predictable, the higher
frequencies (called 'dynamic noise') are more random and more
difficult to predict. In both cases, the theoretical models
needed verification for possible future uses of tethered
platforms. Dr. Gullahorn got good results despite the thwarted
tether deployment.

Related to Dr. Gullahorn's experiment was the study of the
tether oscillations and methods to control them. These
oscillations included longitudinal (up and down motion of the
satellite on the tether), skip-rope (a circular motion of the
tether), transverse oscillation (wave-like tether movement) and
pendulous motion (tether motion caused by the satellite moving
back and forth). Dr. Gullahorn said that they experienced most
of the expected oscillations to a small degree but they were
limited in their attempts to control the oscillation since the
final tether length was too short. The biggest disappointment
was that they could not attempt to control the "skip-rope"
oscillation that didoccur and worsened as the tether was reeled
in. It is the most difficult motion to detect and one method of
control involves actually turning the Shuttle to counterbalance
the movement. This response was rejected by NASA as too risky to
other experiments so late in the mission.

Another major experiment studied the interaction between the
satellite-tether-orbiter system and electric and magnetic fields
in the ionosphere, scientists also examined how a conducting
tether can produce power.

Dr. Gullahorn reported that the science group all hoped to get
onto another Shuttle flight within the next nine months. This
would allow the science teams to stay together and provide more
than enough time to prepare the TSS for another flight. In the
mean time, a smaller expendable version of the system will be
launched on an unmanned rocket in March 1993.

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

Date: Sat, 28 Nov 1992 20:32:16 GMT
From: Ken Arromdee <[e-mail]>
Subject: Environmental group to sue NASA to stop rocket motor fuel testing
Newsgroups: sci.space,talk.politics.space,talk.environment

In article <[e-mail]> phoenix.Princeton.EDU!carlosn (Carlos G. Niederstrasser) writes:
>>     ``Each test, according to NASA, will emit over 350 tons of
>> particulates which release two major gases which we consider highly
>> toxic,'' he said. ``They are hydrogen chloride and aluminum oxide.''
>>     Fontana said NASA has claimed these gases will escape into the
>> atmosphere and will not descend to earth. However, he said his group's
>> studies have shown that hydrogen chloride when mixed with water or
>> moisture forms hydrochloric compound which is highly toxic.

They're nuts.

You know, sodium chloride is toxic too.  Let's ban the Atlantic Ocean.
Unless the group has some reason to believe that it will be concentrated
enough for the acidity to have some effect--in which case they would _say_
so, instead of obliquely referring to concentrated acid and implying it
without actually saying it--they must think that chloride ions are toxic, in
which case we should ban the Atlantic Ocean anyway.

Aluminum oxide, of course, is not even a gas.

Sadly enough, there are enough people who will believe anyone who says that the
government is lying.
--
"the bogosity in a field equals the bogosity imported from related areas, plus
the bogosity generated internally, minus the bogosity expelled or otherwise
disposed of."  -- K. Eric Drexler

Ken Arromdee ([e-mail], [e-mail])

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

Date: 28 Nov 92 18:02:06 GMT
From: Tom A Baker <[e-mail]>
Subject: escape systems
Newsgroups: sci.space

In article <[e-mail]>
[e-mail] (Henry Spencer) writes:

>In article <[e-mail]>
  [e-mail] (John Roberts) writes:
>>
>>Didn't Apollo eventually quit using escape rockets?
>
>I don't have photos handy to check, but as far as I know, every Apollo

He is correct -- every manned Apollo had the escape tower.

In fact, the Shuttle is the ONLY American manned spacecraft to have
flown without an escape system.

Unfortunately, it is the only one that ever needed to use one.

--------------------------------------.--------------------------------------
 Net - [e-mail]  __     | National Space Society is a nonprofit
uucp - uunet!world!tombaker   /  \  / | public organization dedicated to
 BIX - tombaker              /  O  /  | promoting the eventual establishment
 AOL - [e-mail]      /  \__/   | of a spacefaring civilization.
______________________________________|______________________________________

I do not speak for NSS, I speak only for me.

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

Date: Sat, 28 Nov 1992 09:29:41 GMT
From: "Simon E. Booth" <[e-mail]>
Subject: Evil wicked flying bombs!
Newsgroups: sci.space

(stuff about fully-fueled spacecraft crashing into Disney World deleted!)

One thing that's being overlooked is that we've had fully-loaded bombers
flying over our heads with megatons of nuclear firepower on board for years,
and yet we worry more about the safety of the DC-series of spacecraft once
they're in use.

Here in San Antonio we have a wide vareity of planes flying around, including
airliners and C-5's, plus unarmed B-52's, and no one is even phased by this.
I'd have no problem with a nearby spaceport.   (Simon)

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

Date: 28 Nov 92 18:32:33 GMT
From: "Charles R. Martin" <[e-mail]>
Subject: Evil wicked flying bombs!
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Simon E. Booth) writes:


   One thing that's being overlooked is that we've had fully-loaded bombers
   flying over our heads with megatons of nuclear firepower on board for years,
   and yet we worry more about the safety of the DC-series of spacecraft once
   they're in use.

Just a quibble, but it's real damned hard to get a n-weapon to go off in
a crash.  This  is a direct correlary of the fact that it's hard to get
one to go off at all.
--
        Charles R. Martin/(Charlie)/[e-mail]
     Dept. of Computer Science/CB #3175 UNC-CH/Chapel Hill, NC 27599-3175
        3611 University Dr #13M/Durham, NC 27707/[phone]
     "Oh God, please help me be civil in tongue, pure in thought, and able
      to resist the temptation to laugh uncontrollably.  Amen." -- Rob T

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

Date: 28 Nov 92 17:23:51 GMT
From: Steve Collins <[e-mail]>
Subject: Mars Observer Update - 11/13/92
Newsgroups: sci.space

The Mars Observer High gain antenna and solar array ARE independently
steerable in mapping mode. In cruise mode, the Solar array boom has
not been deployed, so it basically body fixed. In principle, the HGA
could be articulated, but the flight software does not currently support{
that capability (it would be a big change...) mynb{_ We have enough link
margin to use the Low Gain Antenna (LGA) until outer cruise transition.
At that time we point the the spacecraft +Y axis ( and therefore the
HGA and Solar array) directly at earth for the remainder of cruise (and
most of the transfer to low orbit...)
              Steve Collins MO Spacecraft Team, AACS (attitude and
articulation)

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

Date: Sat, 28 Nov 1992 15:06:16 GMT
From: Tor Houghton <[e-mail]>
Subject: Pop in space
Newsgroups: sci.space

Hi,


I have been wondering about something for a long time, and I just got
the idea of posting it here.

If a blob of, say Coke, was floating weightlessly in space (inside a
spaceship - normal air pressure), would the "fizz bubbles" go from the
centre to all directions?

Yours,



Tor

--

----------------------------------------------------------------------
email: [e-mail]           "Then we will wonder if machines
                                       will steal each others dreams."

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

Date: 28 Nov 92 09:35:21 GMT
From: "Simon E. Booth" <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>In article <[e-mail]> [e-mail] (Josh 'K' Hopkins) writes:
>>There are ELVs with worse records that shuttle's, but I think there are also
>>a few with better records.
>
>A very few.  The Saturns are the only ones that come to mind.  The last
>few years haven't been good for expendable reliability records.
>
>>Actually, I'm not sure the shuttle has abort modes for the very first part of
>>flight and I know that most people don't consider certain abort modes
>>survivable.
>
>There is no officially-sanctioned abort mode while the SRBs are burning,
>last I heard.  (Oh, you might try SRB jettison or orbiter/ET separation,
>but the orbiter won't survive either one.)  It was looked at during early
>design, and again after Challenger; that is a *hard* problem.
>
>Once the SRBs burn out, you can try an RTLS (Return To Launch Site) abort,
>which is essentially a hypersonic U-turn, but the pilots consider it
>

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

Date: 28 Nov 92 17:45:18 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Brian Stuart Thorn) writes:

>However, if DCX *loses* power on it's way in, then it becomes a falling
>rrock, with *no* control.

DC has flaps and forms a lifting body in its re-entry attitude. It does
have control.

>I'm sure Allen or Henry will say it momentarily... the DCX is very
>unlikely to lose all power on the way in. True enough, but this discussion
>appears to be of worst-case scenarios (at least when directed at the
>Shuttle) so I chose the worst case scenario for a DCX accident, too.

I don't think we are talking about worse case failure. The point is
that it takes a worse case failure to kill people with DC but not
with Shuttle. DC is inherently more safe than Shuttle.

  Allen
--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | "A great man is one who does nothing but leaves        |
|  [e-mail]     |  nothing undone"                                       |
+----------------------147 DAYS TO FIRST FLIGHT OF DCX----------------------+

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

Date: Sat, 28 Nov 1992 17:56:37 GMT
From: Jonathan Hardwick <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

[e-mail] (Brian Stuart Thorn) writes
> If power = cross range ability, then why does the unpowered shuttle have
> a 1,000 mile cross-range capability.
>
> Because it has wings and controllability, if not power. If Shuttle is
> off course, it still has a shot at a safe landing on a long runway
> ssomewhere (not much of a chance, but a chance). If it's headed for
> an apartment complex, the pilot can veer away enough to miss.
>
> However, if DCX *loses* power on it's way in, then it becomes a falling
> rrock, with *no* control. The pilot or computer would be unable to veer
> away from said apartment complex. Look out below.

If the Shuttle loses flight control power on the way in, it'll plow
straight through that apartment complex.  Look out below, and about a
mile in front.

> The Amsterdam 747 disaster has been mentioned much here lately, but in
> most cases, pilots have been able to steer a doomed aircraft away from
> buildings. The Amsterdam disaster took place at night, when visibility was
> poor. The Shuttle rarely lands at night, and presumably neither will
> DCX.
>
> I'm sure Allen or Henry will say it momentarily... the DCX is very
> unlikely to lose all power on the way in. True enough, but this discussion
> appears to be of worst-case scenarios (at least when directed at the
> Shuttle) so I chose the worst case scenario for a DCX accident, too.

Equating total loss of shuttle flight control to total loss of DCX
engine power (ie both very unlikely) would IMHO give relatively equal
catastrophes.  The shuttle impacts along a line, spreading out the
devastation.  The DCX impacts on a point, but any remaining H2/O2 will
add to the destruction at that point.

> Oh, any by the way, I and my family live in Rockledge, Florida. Shuttle
> KSC landings do indeed come VERY close to flying overhead. I'm not worried,
> because if the thing were off course, the Shuttle pilot could point his
> (or her, soon) ship into the Indian River or the marshes out west.

Unless, of course, they lose power...

Jonathan H.

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

Date: 28 Nov 92 17:05:52 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:
>>... I don't see any margin for error in setting down
>>on rocket exhaust. Either everything works perfectly and you survive, or
>>something fails and you topple over and burn, or if you're higher you
>>smack in hard and burn.
>
>Is the concept of "fault tolerance" so foreign?  As Allen has pointed
>out, the DCs can lose 90% of their engine thrust and still land normally.
>As I have pointed out, at landing there is not a lot of fuel on board
>to burn.

Fault tolerance is basically a way of saying multiple redundant systems.
I get this picture of a system so complex and so heavy that it won't fly.
The entire *zero defect* concept grew out of the need to avoid too many
backup systems in spacecraft. SSTO is a thin margin system compared to
ordinary multi-stage rockets. I'd expect *less* redundancy in such a
system. Ok, it uses multiple engines, but that's the norm for any launcher
in current use. They still fail or blow up with disturbing regularity.
It would seem natural to assume that a system with a higher margin would
be more reliable than a system with a thin margin. That leads me to
believe that the SSTO will be *less* reliable than more conventional
approaches.

>>...landing *on* a ball of fire is too damn near landing *in* a ball of fire
>>for my tastes.
>
>The DCs will no more "land on a ball of fire" than a Harrier does.  Harriers,
>with *no* redundancy in the engine systems (as opposed to the DCs' massive
>redundancy), have an eminently reasonable landing-safety record.

I think you might want to have another look at their safety record
compared to other aircraft with similar missions such as the A10.
They're both basically CAS aircraft, but the A10 has a higher
reliability record.

>>I've been in a helicopter with in flight power failure;
>>I've been PIC of a fixed wing aircraft with in flight power failure; and
>>I walked away from both...
>
>Tell it to the Amsterdam 747 crew.  You were fortunate.

Well the odds were very much in my favor. *Most* loss of power incidents
in fixed and rotary wing aircraft are survivable. Several occur in the US
every day, yet you don't hear of several *fatal* aircrashes in the US every
day. *Ocasionally* a loss of power incident results in fatalities, but it's
the exception rather than the rule.

Passive systems like wings are considerably more reliable than complex
active systems like rocket engines. And long slender wings are less
reliable than stubby lifting bodies. The fewer moving parts, and the
shorter the moment arm, the more reliable the system.

Gary

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

Date: 28 Nov 92 20:05:46 GMT
From: Greg Moore <[e-mail]>
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:
>
>>>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.
>
>No problem. We launch it to Mir or Freedom. In a pinch we launch a Soyuz/Atlas
>to meet and fix it.
>

    Ok, assuming we use Titan to launch your Soyuz (only because the number
is here, and a syou admit, an Atlas may not work), your launch cost for your
satellite is now a minimum of 6,000/lb.  This does not include the cost of
your Soyuz.  So, your savings is less.
>>Do we really give a damn what the launch costs if the payload doesn't
>>work after we get it on orbit?
>
>Yes. I can buy and fly between two and three satellites for what it costs to
>build and fly ONE on Shuttle.
>
>If the first fails, I can launch a second and save money over Shuttle. If
>the second one fails, I can send a third and still be ahead of the game.
>

    No, you can LAUNCH 3 satellites for the cost launching one from
the shuttle.  You can't build them though.

>    Allen
>
>--
>+---------------------------------------------------------------------------+
>| Allen W. Sherzer | "A great man is one who does nothing but leaves        |
>|  [e-mail]     |  nothing undone"                                       |
>+----------------------148 DAYS TO FIRST FLIGHT OF DCX----------------------+

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

Date: 28 Nov 92 18:26:39 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:
>
>>The one where you can send a mission specialist, or three, out to kick
>>the damn payload when it doesn't deploy properly.
>
>No problem. We launch it to Mir or Freedom. In a pinch we launch a Soyuz/Atlas
>to meet and fix it.

Mir maybe, but that inclination isn't suitable for many payloads. You'll
have to launch on a Russian rocket from a Russian launch site too. Freedom,
not this decade, maybe not the next. Soyuz/Atlas doesn't exist, Atlas can't
loft a loaded Soyuz anyway, and how do 3 mission specialists stand on
Soyuz's Canadarm and grab the malfunctioning payload?

>>Do we really give a damn what the launch costs if the payload doesn't
>>work after we get it on orbit?
>
>If the first fails, I can launch a second and save money over Shuttle. If
>the second one fails, I can send a third and still be ahead of the game.

Of course you've lost you launch window for your probe for the next
umpty ump years while you build the next one and stack another launcher
because celestial mechanics waits for no man. For less time critical
payloads, you just grit your teeth and watch your insurance costs
spiral out of sight, and your customer go to your competitors. Having
on site startup personnel is a major plus that's worth a considerable
sum of money for expensive space systems.

Expendible throwaways are cost effective for many payloads. That's
why so many payloads are launched that way. But not all payloads
are best handled "cheaply".

Gary

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

Date: 28 Nov 92 20:28:38 GMT
From: Greg Moore <[e-mail]>
Subject: Spacewalk added to shuttle flight, more expected [Release 92-210] (Forwarded)
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Peter Yee) writes:
>
>SPACEWALK ADDED TO SHUTTLE FLIGHT, MORE EXPECTED
>
>        With just over 3 years left before construction of Space Station
>Freedom begins in Earth orbit, NASA has decided to add spacewalks to upcoming
>Shuttle flights when possible, beginning with one during STS-54 in January
>1993.
>
>        The spacewalks, or extravehicular activities (EVAs), will fine-tune
>the methods of training astronauts for assembly tasks in space and increase the
>spacewalk experience levels of astronauts, ground controllers and instructors.
>EVAs will be added to Shuttle missions only when they can be performed with
>no impact on the other objectives and they will be the lowest priority
>activity on each mission.
>


    Amazing, I suggested this a while back, and am glad to see that NASA
is finally doing it.  To me it makes perfect sense for several reasons.

    1) There is still much to learn about assembly in space.  Even if it
is a matter of testing different torque wrenches every flight.  Projects like
EASE and ACCESS and the Intelsat and toher "rescues" are nice, but just
working on basics seems like a must.  Perhaps rather than practicing
"rescues" in a pool of water and then finding you impart more torque than
expected on an Intelstat, you can practice in space and measure what really
happens.  The more data the better.

    2) I think it's important to have as many astronauts as possible
practice these skills in space.  It doesn't make sense to me that only
a select few learn the skills of EVA in space.  Again, the more the
better.

>        For STS-54, astronauts Greg Harbaugh and Mario Runco, Jr.,will perform
>a 5-hour spacewalk evaluating their abilities to move about Endeavour's cargo
>bay with and without large objects; closely align large objects; and install
>large equipment.  In addition, the tests will provide information on the amount
>of time required for various tasks and for the astronauts to become acclimated
>to the spacewalk environment.
>
    Sounds like good practice.


    Let's hope more and more of the flights add spacewalks.
BTW, I'd like to ask a loaded question.  What is the incremental cost of adding
a day to the flight of a mission.  It seems to me that most of the cost of
a shuttle launch is in the ground processing.  Once in orbit, you really only
have to consider consumables and salaries.  Most consumables are cheap, so
the salaries seem to me to be a larger factor.  But would it make
sense from a cost point of view to add a day to most flights, even if it
is just for spacewalks and other "trivial" items.  After all, we spend
millions to get up ther, why hurry back?

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

Date: 28 Nov 92 08:10:11 GMT
From: Jean Yves Desbiens <d40937@aiken>
Subject: Want info: sharp gun/launcher
Newsgroups: sci.space

What I know now : two tubes joined at a right angle, one is
sticking out of the ground; a piston compresses the hydrogen
that serves to propel a payload deadly or not in the tube that
sticks out of the ground. If the design works on a grand scale
it could but a payload in orbit for 50 times less than the current
price. That could surely upset in a very big way the future of
space trade . Why is this the first time a hear about such a
possibly incredible developpement effort: they presently doing
small scale tests. Any other information, please add to
my meager presentation. I really want more info so please
scratch youre powerfull brain USENET and give it to me :-).


--
SEIZE THE DAY, MAKE YOUR LIFE EXTRAORDINARY .  "Dead Poets Society"

Jean-Yves Desbiens                  | [e-mail]
Etudiant en genie informatique      |
Ecole Polytechnique de Montreal Can | To indeed be a god ...,
--------------------------------------------------------------------

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

Date: 28 Nov 92 17:59:56 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 <[e-mail]> [e-mail] (Gary Coffman) writes:
>>We *know* from experience that weight always increases and performance
>>always decreases on the way from the drawing board to the launching
>>pad.
>
>Of course we do. This is why good engineers add margins to their estimates.
>DCY is no different.
>
>Now if you can provide some solid evidence that the margins are too small
>then I'll concede the point. For myself I feel we won;'t know until we
>try.

SSTO margins are thin to begin with, at best DC will loft 10,000 pounds.
The square/cube law says a bigger SSTO would have a greater margin. I
believe that DC is too small to be assured of success in the transistion
from drawing board to flight. I guess if it flies at all some will call
it a success. Certainly multi-stage designs have greater margins, and
few of them have flown on time or on budget while meeting performance
and cost goals. Only one reuseable system is operating, and it didn't
meet either it's performance goals or cost targets as you are fond of
pointing out. Now the same kind of aerospace company is building DCX
under government contract. It's a different company and a different
Agency, but I suspect the result will be similar.

>>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.
>
>Well, a DC1 with SRB's would put a pound into orbit for 1/3 the cost of
>existing expendables. That makes it about 1/6 the cost of the 'larger, more
>capable, system'.
>
>I note with interest that the one parameter you don't seem to feel is relevant
>is cost. So do you work for the government?

Cost is relevant, but I don't accept your cost figures as being anywhere
near reality. You always want to add sunk costs for existing systems and
always use the most optimistic *estimates* for operational costs for
non-existant systems. Naturally the comparisons are flawed. Try using
Shuttle cost estimates at a similar stage in it's development. They would
be just as bogus. Plus when lacking capabilities are pointed out to you,
you just casually wave your hands at some ex-Soviet hardware built by
$40 a month technicians in the former worker's paradise. Those costs
aren't valid anymore, not that they ever were, the accounting was flawed.

>>Note that I've taken on the self-appointed task of throwing cold water
>>on this system.
>
>I have no problem with a devil's advocate. However, I hope future articles
>will have more technical content than 'it hasn't happened yet, so it never
>will'. What specific objections do you have? Do you feel engine performance
>isn't achieveable? Are the margins too small? Do you think the tanks will
>be too heavy? Everybody who has looked at this in detail says a SSTO vheicle
>can be built. 1.5 stage vehicles have been making orbit for 30 years.

Oh I think the proposed system can probably make low orbit, likely with a
small payload. It's getting it *back* in one piece and turning it around
like an airliner at airliner costs that I doubt.

>Why exactly are you right and they wrong?

It's too ambitious. Too many things have to work out right for the
system to meet it's performance goals. Complex systems never work
the way you expect until you are *way* down the learning curve. There
are too many things about DC that are fast track. It will be incredible
luck if enough of them mature together to make the system meet it's
specs. I'll be very surprised if it meets a tenth of it's goals at
ten times it's projected operating cost.

>>That's why SSTO has never been seriously considered before.
>
>You should read up on the history a bit more. SSTO's have been on the
>drawing boards for years.

Yes, and they've *stayed* on the drawing boards for very good reason.
It's very high risk technology. Now we've got to take risks if we want
to advance. I think DCX is a good program in that regard. What I find
suspicious is the *assumption* that a follow on DC-1 is on the horizon
and that it will be the wonderfully cheap and reliable system you and
Henry claim. More likely is that DCX will have to be followed by DCX-1
DCX-2.....DCY, DCY-1, ....DCY-77, DCZ, etc before we see a DC-1 like
you so glowingly describe. These aren't airplanes. They are orders of
magnitude more energetic and exotic. No one has ever done some of the
things DC will have to do and few things work right the first time
unless cubic money is poured on them. That in particular is supposed
to be where the DC program will be different. I find that hard to
believe.

Gary

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End of Space Digest Volume 15 : Issue 468
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