Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V15_4/V15NO466.TXT

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Date: Sat, 28 Nov 92 05:00:02
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #466
To: Space Digest Readers
Precedence: bulk


Space Digest                Sat, 28 Nov 92       Volume 15 : Issue 466

Today's Topics:
             Kuiper belt planetesimals and Planet X claim
                      Magellan Update - 11/20/92
                   Need Info On Hubble!!!!!!!!!!!!!
                    Scuttle replacement  (2 msgs)
               Scuttle replacement (really about wings)
                      Shuttle Computer Problems
                     Shuttle replacement (8 msgs)
                         Space suit research?
                 WE NEED PICTURE OF THE SOLARSYSTEM!!
                    What comes after DC-1 (2 msgs)

    Welcome to the Space Digest!!  Please send your messages to
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----------------------------------------------------------------------

Date: 27 Nov 92 20:23:15 GMT
From: Tom Van Flandern <[e-mail]>
Subject: Kuiper belt planetesimals and Planet X claim
Newsgroups: sci.astro,sci.space

[e-mail] (Andrew C Goldish) writes:

> Now that objects have been sighted that could possibly prove the existence
> of the Kuiper belt, ...

     The one such object recently sighted apparently is not a Kuiper belt
comet, but a possible member of the Saturn family of asteroids or comets. All
other searches for Kuiper belt objects have so far proved fruitless.  And the
reasons for expecting a Kuiper belt at all have now been called into
question.  The whole concept is close to being ready to file away next to
"cold fusion."

> ... is it possible that the combined gravity of all the planetesimals (at
> least those near Neptune) is enough to perturb Neptune's orbit?

     The unexplained perturbations in the outer planets cannot be accounted
for by objects distributed in a ring or shell.  As far back as the 1950's an
upper limit of 0.1 Earth masses was set on the mass of any trans-Neptunian
ring at about 50 au, where the Kuiper belt is supposed to reside.


and [e-mail] (Henry Spencer) writes:

> 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.

     This is true.  But 20th century data covers only half a revolution of
Neptune, and does not constrain the orbit very well.

> 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.

     Not exactly.  The model that Pluto and Charon are escaped former
Neptunian moons has led to the prediction that the undiscovered 3-to-5-Earth-
mass object that stripped them away and disrupted Triton and Nereid's orbits
is actually Planet X, which must then be in a high-inclination, high-
eccentricity orbit as a result of its encounter with Neptune.  The fact that
the unexplained perturbations in Neptune are consistent with high-i, high-e
simply fills out a consistent picture.  See Harrington, R.S. and Van
Flandern, T., "The satellites of Neptune and the origin of Pluto", Icarus 39,
131-136 (1979).  See also "Worlds apart", a Focal Point debate between W.B.
McKinnon and myself in Sky&Tel. 82, 340-341 (1991).  -|Tom|-

--
Tom Van Flandern / Washington, DC / [e-mail]
Meta Research was founded to foster research into ideas not otherwise
supported because they conflict with mainstream theories in Astronomy.

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

Date: 27 Nov 92 04:31:47 GMT
From: hiroki hihara <[e-mail]>
Subject: Magellan Update - 11/20/92
Newsgroups: sci.space,sci.astro

In article <[e-mail]> [e-mail] writes:
>
>Can I quote you on that?

All right.  E-mail is appreciated.


-- NEC Space Systems Development Division
   $B1'Ch3+H/;v6HIt!!Ek:\5!4o3+H/It(J
   Hiroki Hihara
   $B[X86(J $B90<y(J

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

Date: Fri, 27 Nov 1992 13:27:31 GMT
From: John Wogan <[e-mail]>
Subject: Need Info On Hubble!!!!!!!!!!!!!
Newsgroups: sci.space

I'm new to the nets, and although aware of the Hubble (and your
discussion of it), I don't have any specifics.

I'd like general information about it e.g. date of launch etc.

Some other of my questions include :

How good are the images we get back?

Is there supposed to be a shuttle mission to repair it? If so, when?

Please would you e-mail me the info.

Thanx,

    J.W.

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

Date: Fri, 27 Nov 92 12:48:51 -0600
From: [e-mail] (Phil G. Fraering)
Subject: Scuttle replacement

\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

1. Of the three accidents that have happened in New Orleans involving
airliners, in one was the airliner able to glide to safety. In the other
two, there was severe loss of life.

2. If you checked, you'd probably find the energy density of jet fuel
to be higher than lox/lh2; the reason that's a good rocket fuel is because
of the low mass of the exhaust.

3. An abort mode for landing is a good prerequisite for safety for
an aircraft that needs a mile of concrete to slow down and stop after
touching down at 150 mph.

4. Autorotation doesn't work worth a damn. The way I've heard it, if
the engine goes out, maybe the pilot of the helicopter will get very
lucky and be able to autorotate...

--
Phil Fraering
"...drag them, kicking and screaming, into the Century of the Fruitbat."
<<- Terry Pratchett, _Reaper Man_
PGP key available if and when I ever get around to compiling PGP...

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

Date: Fri, 27 Nov 1992 19:37:55 GMT
From: Henry Spencer <[e-mail]>
Subject: Scuttle replacement
Newsgroups: sci.space

In article <[e-mail]> [e-mail] ("Phil G. Fraering") writes:
>3. An abort mode for landing is a good prerequisite for safety for
>an aircraft that needs a mile of concrete to slow down and stop after
>touching down at 150 mph.

As Max Hunter says:  "if the Wright Brothers had had engines with the
thrust:weight ratio of modern rockets, the word `runway' would not
exist in the English language".
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: Fri, 27 Nov 92 12:42:43 -0600
From: [e-mail] (Phil G. Fraering)
Subject: Scuttle replacement (really about wings)

\>>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

Yah, wings on it, the better for the microburst to slam it into
the ground with!

New Orleans has had airliners crash shortly after takeoff with heavy
loss of life _twice_ due to microbursts (or so they think; they can't
FIND the first one to find out what happened since it dived into Lake
Ponchatrain at immense speed), the second time with very heavy loss of
life on the ground.

If we can put up with that sort of risk so a bunch of stupid yankees
and rednecks and other assorted tourists can come and get shitfaced
drunk in the quarter (something they can do perfectly well at home
WITHOUT going to New Orleans) then we can put up with a lesser risk to
explore space.


--
Phil Fraering
"...drag them, kicking and screaming, into the Century of the Fruitbat."
<<- Terry Pratchett, _Reaper Man_
PGP key available if and when I ever get around to compiling PGP...

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

Date: Fri, 27 Nov 92 12:31:27 GMT
From: [e-mail]
Subject: Shuttle Computer Problems

Since I worked with (and designed and implimented a product line that
is still in use) real time control systems for nearly a decade, I can
suggest some more prosaic things to look for than SEU's.

Power line noise and RF pickup are, in my experience, the number one
and two sources of problems of unexplained lockups, bad bits and
such.

In once instance, I had extrememly narrow high voltage spikes that
got onto a cable from a UPS. There was a very slight flaw in the
sheilding, and we were in a room with heavy electrical equipment. The
pulse had only one effect... it caused the Interrrupt Enable bits on
all the DLV-11 (LSI-11 serial interface boards) to clear. So the
system worked but it stopped talking to it's console...

In another case, there was an improperly grounded input to a logic
gate on a board handling data communications. A nearby aircraft
beacon swept the lab once every 30 seconds, and inserted one extra
bit in a phase shift keyed bit stream. That one drove us *MAD* for
nearly a month.

Another hair puller had to do with a proprietary 6502 controller
being debugged using an off-board ICE. The system was working fine
until we upgraded the RTOS... and then we started getting random
crashes. We thought it was a code bug, but finally tracked it down to

misexecution of the interrupt lock instruction going into the
scheduler critical region. Another week of 24 hour workdays and we
found that unless we had a *HUMUNGOUS* ground wire, it had enough
impedance to act as an antenna that picked up the RF output of the
6502 processor... and then fed it back to the processor. We literally
had a bug that had to do with RF coupling of the sequence of
processor instructions to itself...


So before you go blaming cosmic rays at ground level, take a good
HARD look at the power and ground. Are you using any heavy electrical
equipment in the vicinity that you haven't been using before? Is
there anything that changed in the environment of the rear bulkhead?
Could there be unnoticed damage to a shielded power cable? Are there
any high power NavAids being tested in the vicinity?

I'd appreciate knowing if I was of any assistance.

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

Date: 27 Nov 92 14:16:45 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 bit less zenophobia please! what the hell do you think an airliner is?
>>
>>Something with *wings* on it.
>
>Just think of DC-1 as a high-performance helicopter.

Even they have rotary wings. The reason I keep harping on this is that
landing *on* a ball of fire is too damn near landing *in* a ball of fire
for my tastes. 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. 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.

Gary

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

Date: 27 Nov 92 16:34:02 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Brad Whitehurst) writes:

>    Just out of curiosity, what part of the DC-X do you work on?

I don't work on DC and have no financial or technical involvement. I simply
think it is something which needs to be pushed as one of the few good
projects out there.

>    If you are versed in the mechanical/structural end of the DC
>series, I was wondering how you are addressing the issue of structural
>robustness of the landing gear and associated airframe.

The landing gear is simply 4 legs which come down and support the
vehicle. I don't know how much stress they can take.

>From how high
>up is this thing supposed to survive without damage if (for instance)
>a sudden loss of thrust is experienced?

It would be very hard to loose that much thrust. DCY engines should put
out about 1.3 million pounds of thrust but on landing it only weighs
100K pounds. 90% of available thrust cold be lost it still could land.

If somehow total thrust was lost (which seems very unlikely) then the
structure provides considerable protection for crew and payload.

>I recall that structural
>integrity and resistance to low cycle fatigue without excessive weight
>is an old bugaboo in aircraft landing gear.  On a civil jet I guess it
>is not so bad, but weight is almost always a big factor with military
>jets' gear.

DC should be viewed as a civil jet, not a military one. But remember
that aircraft landing gear needs to do much more than a DC landing
strut. DC landing gear need only absorb a small amount of downward
acceleration and support the vehicle. Aircraft landing gear need to
do that plus provide suspension, steering, and breaking for a vehicle
weighing a fair fraction of a million pounds and moving 80 MPH.

>Basically, I guess some of your comments seem like a
>toss-off: "Hey, this is easier than building a jet" whereas even civil
>jets sometimes take agonizing months or years to get certificated.

I'm sure that will be the case for an operational DC1. I also believe
that this is not a risk free project. However at the same time, everybody
who has looked at it, from the Aerospace Corporation to NASA have said
it CAN be done.

>I think there's a lot of good ol' mechanical gremlins lurking in the
>shadows when you try scaling this thing up, then operating it like a
>"space truck".

Maybe your right. If we all listen to Gary we will never find out.

Suppose it is too heavy to take off? We still will have a very valuable
testbed for future work. Over time we can incrimentally improve it
to the point where it will function.

   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: 27 Nov 92 14:52:18 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:
>>>No, gliders don't burn on impact; they just go "crunch".  It's still
>>>just about as fatal.
>>
>>Actually it's not. The safety record for gliders is quite good, and they
>>don't burn blocks of apartments on the ground when they do smack in
>>like the *powered* Navy jet did in Marietta last year, or the *powered*
>>C-130 that *burned* the hotel in Evansville did this year, or the Israeli
>>jet freighter in the Netherlands.
>
>I was thinking of fatalities to those on board.  I guarantee you that a
>750,000lb glider would kill people if it hit an apartment block, although
>not quite as many as a 747 heavy with fuel.  (Whether the 747's engines
>were running is quite irrelevant.  In fact, that particular 747's *problem*
>was that it was half glider.)  Certainly if that had been a returning
>shuttle orbiter, it would have killed a lot of people -- between fire and
>poisoning -- even though the orbiter itself was gliding.

Well the Shuttle doesn't weigh 750,000 lb, it's max rated landing
weight is 240,000 lb. It also voids RCS and OMS fuel during descent
so that it lands with nearly dry tanks. Only APU fuel is on board in
any quanity. Most likely failures are a short approach or a wheels up
landing. In case of a belly landing, the Shuttle would probably have
to be declared unserviceable, but the crew would likely survive and
there would likely be no fire or explosion. A really short approach
would likely rip the landing gear off and the results would be much
like the belly landing above, though with more structural damage.
Worst case would be a total miss of the runway. In that case the
Shuttle might tumble. The vehicle would be a total writeoff, and
the crew could suffer severe injury, or be killed. If the Shuttle
wound up at Disney World because of a navigation or control
failure, it would be about like a train wreck. Lots of physical
damage in it's path, but no serious fire from Orbiter fuels. There
might be fire from combustion sources on the ground of course.

>Please don't compare light sporting aircraft that fly only in good weather
>with operational commercial cargo/passenger aircraft that are two orders
>of magnitude larger.

Fine, use the large cargo gliders from the Normandy invasion as your
baseline. Many of them crash landed. There were no fires, and most
of the troops and their gear, including explosives, survived. Being big,
or operating in bad weather, doesn't make gliders any more prone to fire
and explosion when they crash. Lacking tanks of liquid fuel and hot engines
does make them less prone to fire and explosion.

Gary

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

Date: Fri, 27 Nov 1992 16:58:53 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Steinn Sigurdsson) writes:

>   We spent half a billion $$ to recover $75 million worth of satellites. Only
>   a NASA employee could consider that a good deal.

>Come on Allen, you can't charge the whole cost of the flight to
>the rescue, this has been hashed out a dozen times -

On the mission in question Shuttle did little if anything else.

But I would be interested in seeing your cost model which justifies
satellite rescue. Proponents of Shuttle haven't been able to offer
one. BTW, just picking an application you like and charging it the
marginal costs doesn't cut it since the other users won't like it.

Also remember that recovered satellites aren't worth as much as new ones.
I believe the two satellites in question where sold for about half price.

>   ERROR: You are assuming LDEF as is was the one and only way to get this
>   infromation. This is incorrect.

>True, but just exactly who was doing it a different way?

The Russians.

>As LDEF is it
>as of now should not all the benefit derived from it be credited to
>the shuttle program?

Along with all the blame. Including the tens of millions wasted and the
experiments ruined because of the unreliability and expense of Shuttle.

>Irrespective of whether it would have been
>better&cheaper some mythical other way?

Look, just because it doesn't exist today doesn't make it mythical. If you
want to show that it CAN'T be done, then do so. Engineers project the
capabilities of machines not yet built all the time. I do it myself for
the proposals I write and projects I work on.

    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: 27 Nov 92 17:39:14 GMT
From: Henry Spencer <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

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.

>...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'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.

>...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.

That would be a good description of a runway landing too.  A vertical
landing is much more forgiving.  Yes, the DCs have some failure mechanisms
that airplanes lack -- total loss of power is bad -- but they also are free
of a whole slew of failure mechanisms peculiar to aerodynamic lift.  They
don't have to worry about things like asymmetric slat deployment (which
killed all aboard the Chicago DC-10).
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: 27 Nov 92 19:49:00 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Gary Coffman) writes:

>Noris the proposed DC-1 anything like a
>helicopter which can autorotate if there is a power failure.

Helicopters have a single point failure: the tail roter. DC does not have
a single point failure.

>Nor do either of these systems require high performance rocket fuel. On a

Perhaps you could answer a question: if this 'high performance rocket fuel'
is so dangerous why is it that about a million pounds of the stuff
couldn't blow up a Shuttle orbiter only inches away from it?

>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?

Aricraft need to abort, VTOLs don't.

    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: 27 Nov 92 20:08:55 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

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.

>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.

    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: 27 Nov 92 20:17:17 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Gary Coffman) writes:

>Well the Shuttle doesn't weigh 750,000 lb, it's max rated landing
>weight is 240,000 lb.

Don't quibble. Henry's point was that a Shuttle colliding with an apartment
building would kill lots of people. do you agree?


>>Please don't compare light sporting aircraft that fly only in good weather
>>with operational commercial cargo/passenger aircraft that are two orders
>>of magnitude larger.

>Fine, use the large cargo gliders from the Normandy invasion as your
>baseline.

Sorry that doesn't meet Henry's criteria. Those gliders only flew during
very good weather. As it is, they only saw very limited use because they
where judged too dangerous.

   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: Fri, 27 Nov 1992 18:02:53 GMT
From: [e-mail]
Subject: Space suit research?
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Frank Crary) writes:
>In article <[e-mail]> [e-mail] (Charles R. Martin) writes:
>>Anyway, actually a significant number of people
>>develop altitude sickness even at Aspen and *lower* altitudes.  Growing
>>up in Alamosa, I know there were people there who never adapted and had
>>to leave for medical reasons even though they were to all appearances
>>healthy; Robert Heinlein's wife Ginny had altitude sickness in Colorado
>>Springs that eventually forced their move to California.
>
>That's true enough, and why I added that such adaptability could
>easily be made part of the medical qualifications for spaceflight. I've
>never heard of someone who adapted to the lower oxygen levels, and much
>later expreienced problems. As far as I know, once someone adapts
>there aren't later problems.

    Not  quite the  same subject, but I   thought that the inability
of  Spanish  women  (who otherwise adapted to   local  conditions)  to
carry  children to term at high altitudes prevented  the Spanish  from
displacing the Andean natives.

                        James  Nicoll

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

Date: 27 Nov 92 15:38:14 GMT
From: Tore Dalsgaard <[e-mail]>
Subject: WE NEED PICTURE OF THE SOLARSYSTEM!!
Newsgroups: sci.space

HI!
We are a group from Roskilde University, wich is working with the subject
astronomy/Astrology in this semester.
We need pictures our solarsystem and pictures of our planets.
If you have some or an FTP adresse then mail to us.

Tore Dalsgaard
Roskilde University, Denmark
E-mail: [e-mail] or [e-mail]

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

Date: Fri, 27 Nov 1992 09:31:02 GMT
From: "Herity D." <[e-mail]>
Subject: What comes after DC-1
Newsgroups: sci.space

[e-mail] (Herity D.) writes:

>Soft landings on some satellites would also be possible.

I've re-thought that, and I now realise that this is not really on, for
the following reasons.
There would be little or no fuel left over after leaving LEO for
interplanetery transfer.
After a transit of several years to an outer planet, cryogenic fuel
would have boiled off.
DC-1 is designed to areobrake with almost empty tanks, not with fuel
sloshing around.

However, I also realise that a DC-1 could launch an interplanetery payload
from LEO and return to earth. So you don't have to expend the vehicle.

The DC goes initially into an elliptical orbit from LEO. At apogee, it
starts the main boost, accelerating past the earth, rather than away from
it. At the end of the boost, it is travelling at interplanetary speed,
but at an atmosphere grazing altitude. It then releases the payload and
dips into the atmosphere to aerobrake.
--
================================================================================
| 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: 27 Nov 92 20:02:40 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: What comes after DC-1
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Gary Coffman) writes:

>>>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.

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.

>SRBs may be the only way the proposed DC-1 ever gets to orbit.

In an absolute worse case you just might be right. But then in a few years
test flying we should be able to reduce the weight enough to make it
practical.

>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?

>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.

Why exactly are you right and they wrong?

>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.

   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----------------------+

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End of Space Digest Volume 15 : Issue 466
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