Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V15_4/V15NO469.TXT

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Date: Sun, 29 Nov 92 05:03:23
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #469
To: Space Digest Readers
Precedence: bulk


Space Digest                Sun, 29 Nov 92       Volume 15 : Issue 469

Today's Topics:
                      Evil wicked flying bombs!
                 Mars: "unusual" landforms, lat/long
                             Pop in space
                     Scuttle replacement (3 msgs)
                    Shuttle replacement (11 msgs)
                    Want info: sharp gun/launcher

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

Date: Sat, 28 Nov 1992 23:39:43 GMT
From: James Davis Nicoll <[e-mail]>
Subject: Evil wicked flying bombs!
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Charles R. Martin) writes:
>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.


    N-weapons, at least in NATO, are also carefully designed to not
go off unless the  proper procedures are followed. If  you don't know the
PAL codes, improper arming should leave the user with a mildly  radioactive
paperweight. Modern nukes have spiffy electronic 'locks' which are said to
be next to impossible to crack. I think most of the older devices with
mechanical security devices have been retired.

    If someone acquired a nuclear device illicitly, to use it would
require  access to  the  proper PAL code  as well.
                            James Nicoll

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

Date: 28 Nov 92 16:49:18 -0600
From: [e-mail]
Subject: Mars: "unusual" landforms, lat/long
Newsgroups: sci.space

Anybody out there have the latitude and longitude coordinates of the
"unusual" Martian landforms which have been discussed in the popular
press in recent years?

Specifically, I'm looking for the lambda and phi (Martian latitude
and longitude) coordinates of:

The "Face" in Cydonia
and
The "Pyramids" in Elysium

(I'm writing a novel that's partly set on Mars, and I'd really like
to know where these minor "tourist attractions" are.)

Thanks in advance,
Ken Barnes

--
*.x,*dna**************************************************************
*(==) Ken Barnes, LifeSci Bldg.                                      *
* \'  [e-mail]                                    *
*(-)**Memphis,TN********75320,[e-mail]**********************
"When I was a boy I was told that anybody could become President;
I'm beginning to believe it."--Clarence Darrow

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

Date: Sat, 28 Nov 1992 19:39:35 -0500
From: "Jonathan R. Ferro" <[e-mail]>
Subject: Pop in space
Newsgroups: sci.space

[e-mail] (Tor Houghton) writes:
> 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?

Yes, the bubbles would have no preferred direction to escape towards in
freefall IF they were to form in the center of the "blob", but it is
more likely that no bubbles would form at all or only on the blob's
surface.

The reason that bubbles form in a glass of soda on the Earth's surface
is because the soda is in contact with the glass.  The glass surface
undoubtedly contains impurities, oils, microscopic scratches, etc.,
which are more favorable as "nucleation points" for the bubbles than
just the middle of the bulk liquid.  Bubbles of gas (CO2, in this case)
form at these nucleation points and break off to head for the surface
when they grow large enough so that buoyant forces dominate the surface
tension forces.  Chemists often use this property when they add small
chips of porcelain, or "boiling stones" to liquids that they are going
to boil to cause the vapor bubbles to be generated more evenly.

So, it is more likely that a blob of soda in freefall would not bubble,
but just gradually become flat as the CO2 diffuses from the liquid out
into the air.  It would be interesting, instead, to flick a boiling
stone into the blob to watch the nucleating bubbles spread away from it.

-- Jon Ferro               Einsprachigkeit ist heilbar

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

Date: 28 Nov 92 18:33:20 GMT
From: Gary Coffman <ke4zv!gary>
Subject: Scuttle replacement
Newsgroups: sci.space

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

That's right. Instead we have the farmer standing next to his burnt
haystack saying, "I hope you're insured Mr. Wright." :-)

Does anyone remember the pictures of the balloon with four helicopters
attached crashing and burning. Control is difficult when your lift
comes from several active sources.

Gary

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

Date: Sat, 28 Nov 92 17:27:37 -0600
From: [e-mail] (Phil G. Fraering)
Subject: Scuttle replacement

>Does anyone remember the pictures of the balloon with four helicopters
>attached crashing and burning. Control is difficult when your lift
>comes from several active sources.

Last I heard (although I may be wrong) the failure was caused by
a structural problem and not an engine control problem...

>Gary

--
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: 28 Nov 92 23:04:08 GMT
From: Henry Spencer <[e-mail]>
Subject: Scuttle replacement
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Gary Coffman) writes:
>Does anyone remember the pictures of the balloon with four helicopters
>attached crashing and burning. Control is difficult when your lift
>comes from several active sources.

Gosh, do you think Mr. Korolev ever heard of this?  His "A" booster,
with *twenty* main engines firing at liftoff, has flown 1000+ times
successfully, and has launched every Soviet manned mission (except
possibly Soyuz 1, which some people think went up on a Proton).  It
is probably the most reliable space launcher on Earth, because it's the
only one that's been thoroughly tested.

Initial debugging of such things can be interesting, of course.  Mind
you, the only US launcher with an absolutely, unquestionably perfect
record had 8 main engines (the Saturn I/IB), and the runner-up had
5 (the Saturn V, whose second test was less than a complete success).

Control can be tricky when your lift comes from several *aerodynamic*
sources.  It's a solved problem when the lift producers are rocket engines,
which are much easier to control.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: 28 Nov 92 18:43:51 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:
>
>>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?

When the Navy jet hit the apartment complex, the impact didn't kill anyone
but the pilot. The *fire* did the bulk of the damage. Coming in on empty
tanks does wonders to reduce fire risk. Sure, a Shuttle hitting an apartment
complex might kill some people in it's path. It's big and it's moving fairly
fast. But it won't burn the whole block to the ground like a vehicle with
fuel in it's tanks and hot engines to ignite it.


>>>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.

Actually they landed at night with no lights or runway. That's because
Ack Ack makes very hostile weather. Most of the troops *still* survived
the landings in shape to fight even though several of the gliders tangled
with hedgerows. They saw limited use because we don't stage Normandy
invasions every day.

Gary

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

Date: 28 Nov 92 19:28:22 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] (Brian Stuart Thorn) writes:
>
>>However, my argument was that the RL-10, which will power the DCX, has
>>failed twice in flight in the past 18 months.
>
>If the same failures happen to DCX then all they need do is shut down the
>engines which did start, find and fix the problem, and fly again. This will
>result in RL-10's with one less malfunction and a more reliable system.

They're at 10,000 feet, closing fast with the ground, and half their
engines don't start (that's what happened in the recent failures). So
they just stop the others, get out and fix the problem, and proceed
to land? I don't think so. I think they'll smear all over the landscape
before they even have time to realize they have a problem. A failure
on the pad is one thing. A failure coming down is something altogether
different. Yeah I know they're lighter coming down, but asymetric
thrust still sounds bad when you're close to the ground and have to
make a perfect 4 point touchdown. Can you gimbel the remaining engines
enough to still stay perfectly upright as you descend? Can you do
it quickly enough if the failure is close to touchdown?

Actually I suspect they'll static test the engines a bunch of times
before trying to light them in flight. But let's consider a different
scenario. DC-1 is supposed to receive airliner grade servicing. We
know that airliners receiving that grade of service have engines *fall
off* in flight. Suppose a fuel feed line fatigues from multiple flights.
It wasn't X-rayed before flight because this is airliner grade servicing.
So the thing lets go as they pass through 10,000 feet on their way to
a landing at O'Hare. A couple of tons of rocket fuel starts streaming
down among the firing engines as they pass over the Loop. What's their
abort mode? Or assume it's at takeoff and they have a full fuel load.
Airliner servicing isn't zero defects because that costs too much and
stresses are fairly low and an engine falling off or a fuel line rupture
is generally survivable due to the presence of wings and a fire bottle.
Spacecraft stresses are much higher and DC-1 will glide like a flaming
rock. This is high risk stuff, not airliner grade hazard at all. It
costs a lot more to do zero defects, recall that standing army at the
Cape? And things still sometimes go boom. DC-1 better stay away from
populated areas until it's been crash tested a few times.

Gary

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

Date: 28 Nov 92 21:45:25 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

In article <7#[e-mail]> [e-mail] (Greg Moore) writes:

>>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.

No, my launch cost is now a minimum of $3,000/lb. Most of the time I won't
need the Soyuz so i won't launch it.

>This does not include the cost of your Soyuz.  So, your savings is less.

Using your numbers I am saving about $4,000 for each and every pound I put up.
I'll bet if you where spending YOUR money that's the way you would pick.

>>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.

Sorry. I can build and launch a typical satellite for ~$200 million. $600M
is a low cost for a Shuttle launch. (Others may claim the cost closer to
$500M but those people are only considering operational costs and ignoring
NASA overhead, orbiter depreciation, development amortization, and other
costs which easilly add over $100M per flight).

   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 22:04:24 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

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

>>>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.

Only a factor for interplanetary flights. To date they have done just fine
on expendables. With the billions saved, we can launch more missions.

In fact, with the money saved by not using Shuttle we can afford to build
and launch two or more probes. The end result will be more science done.

>For less time critical
>payloads, you just grit your teeth and watch your insurance costs
>spiral out of sight,

Come on now, think. Insurance costs for a system which is 97+% reliable
(like current expendables) are far less than systems which are only a
little more reliable yet cost three times as much.

>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.

The companies who went with Shuttle went out of buisness long ago. They
paid too much for launch costs.

BTW, with the money saved using expendables my customers are building a space
station where they do an order of magnitude more science for less cost than
using your Shuttle. One fo the things they plan to do is integrate their
own spacecraft at the station. This greatly reduces their costs and allows
for on site repair when needed. Needless to say, they are very glad they
didn't waste the money they are building the station with on Shuttle.

>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".

Example?


   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: 28 Nov 92 22:18:24 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

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

>They're at 10,000 feet, closing fast with the ground, and half their
>engines don't start (that's what happened in the recent failures).

Not quite. The engines in question failed on the first attempt to fire them.
On return the engines would have already fired which greatly increases the
odds of successful firing.

But let's say it happened anyway. A landing DC should weigh about 100K
pounds. All engines operating together produce 1.3 million pounds of thruse.
So if half the engines fail, we will have 'only' 650,000 pounds of thrust
or about six times more than what we need.

I would say this will result in a normal landing.

>different. Yeah I know they're lighter coming down, but asymetric
>thrust still sounds bad when you're close to the ground and have to
>make a perfect 4 point touchdown.

You don't need a perfect touchdown.

>Can you gimbel the remaining engines
>enough to still stay perfectly upright as you descend? Can you do
>it quickly enough if the failure is close to touchdown?

I would say this is a trivial problem.

>off* in flight. Suppose a fuel feed line fatigues from multiple flights.
>It wasn't X-rayed before flight because this is airliner grade servicing.
>So the thing lets go as they pass through 10,000 feet on their way to
>a landing at O'Hare. A couple of tons of rocket fuel starts streaming
>down among the firing engines as they pass over the Loop. What's their
>abort mode?

The engine control system will notice the loss of thruse in the affected
engine. That engine is shut down.

    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: 28 Nov 92 20:27:34 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:
>
>>Nor is 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.

How about a main fuel line rupture?

>>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?

Actually it seemed to do a pretty good job of making that flight
unsurvivable. Note that tanks full of JP4 can't blow up in flight
either. Burn a little maybe, but not explode. Shuttle main tank
didn't explode because the fuel and oxidizer weren't mixed well.
It did burn in a hell of a hurry. A major fire in flight is
unsurvivable anyway. That's the glider's advantage, it can't burn
in flight.

>>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.

That's funny. We've had to abort helicopter landings many times. Some
idiot walks out on the pad, some yo-yo parks in our space, a gust of
wind blows us off course, etc. We often have to hover or go back up a
ways, look for another spot, try the approach again, even fly around
for a while until we find one or the pad is cleared. Wind gusts are
the worst. You almost always have to go back up a ways, get straight,
and try again. That all takes fuel margin.

Gary

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

Date: 28 Nov 92 23:53:49 GMT
From: Henry Spencer <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Gary Coffman) writes:
>>If the same failures happen to DCX then all they need do is shut down the
>>engines which did start, find and fix the problem, and fly again. This will
>>result in RL-10's with one less malfunction and a more reliable system.
>
>They're at 10,000 feet, closing fast with the ground, and half their
>engines don't start (that's what happened in the recent failures). So
>they just stop the others, get out and fix the problem, and proceed
>to land?

You're posing a different problem, since the recent failures were RL10s
that would not ignite at all, and complete ignition failures on a DC get
found at launch.  *That's* when you stop the others and then fix the
problem for the next flight.

However, it's still nothing very serious.  If half their engines don't
start, they land normally -- half is plenty -- and then proceed as above.

>... Yeah I know they're lighter coming down, but asymetric
>thrust still sounds bad when you're close to the ground and have to
>make a perfect 4 point touchdown. Can you gimbel the remaining engines
>enough to still stay perfectly upright as you descend? Can you do
>it quickly enough if the failure is close to touchdown?

It is certainly feasible; single-engine failures in multiply-redundant
stages have happened without dire consequences, e.g. the second Saturn V
flight.  The DCs also have an extra dimension of controllability to use
in such situations, since their engines are throttlable.

You can always postulate a failure too severe to be handled.  Asymmetric
lift is bad too; how many aircraft have landed safely with one wing gone?
(I do know of one example.)

>... airliners receiving that grade of service have engines *fall
>off* in flight. Suppose a fuel feed line fatigues from multiple flights.
>It wasn't X-rayed before flight because this is airliner grade servicing.
>So the thing lets go as they pass through 10,000 feet on their way to
>a landing at O'Hare. A couple of tons of rocket fuel starts streaming
>down among the firing engines as they pass over the Loop. What's their
>abort mode? ...

Or suppose that #3 engine on a 747 somehow fails messily, and wipes out
#4 while it's at it, and this happens with a heavy fuel load over Amsterdam.
What's their abort mode?  Answer:  they die and so do a lot of others.
The question is not "can unsurvivable failures occur?" but "how likely is
such a failure?".  Something meant to be certified as an airliner, e.g.
DC-1, will have to be built to keep the probability of such failures low.
That means, as with airliners, careful analysis of fatigue lives of parts
and inspection/replacement schedules set up to avoid problems.  (It also
means, as with airliners, that there will probably be an occasional crash
due to unanticipated problems.)

>Spacecraft stresses are much higher...

Spacecraft stresses are *zero* for most of the flight.  The high stresses
last a few minutes per flight.  Hardware with a fatigue life of (say)
1000 hours wouldn't even be legal on a 747, but should last a DC-1 its
entire operating life.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: Sun, 29 Nov 1992 00:23:54 GMT
From: Donald Lindsay <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

[e-mail] (Gary Coffman) writes:
>DC-1 is supposed to receive airliner grade servicing. We
>know that airliners receiving that grade of service have engines *fall
>off* in flight.

I'm getting tired of your attacks on the DC. It's untried, sure.
(It isn't even built yet - sure.) But you seem to be on some sort
of crusade to prove that VL SSTO is inherently dangerous.

There are a million airplane takeoffs a day (or was it a week - no
difference). So, it's not surprising that we *regularly* hear about
one-in-a-million events! If SSTO technology, or *any* *other*
technology, were doing a million orbital insertions a week, we'd
similarly hear about a lot of splatted spacefarers. Sure.

But initially, the DC series will be static tested. Then, unmanned
hovering. Then up to the stratosphere and back, unmanned. And that
same progression is planned for *each* *craft* that's built, and the
per-craft tests will be done at some sort of test range. Having been
through that, yes, some pump may be stressed and just ready to burst.
But the computed odds are a *lot* nicer than any non-SSTO
human-capable technology offers. (With the exception, of course, of
the technologies such as skyhooks, which rely on unobtainium.)

So, lighten up. Perhaps instead you could concentrate on how to
build an even better SSTO.
--
Don        D.C.Lindsay    Carnegie Mellon Computer Science

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

Date: 29 Nov 92 00:29:35 GMT
From: Brian Stuart Thorn <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

>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.                                            ^^^ ^^^^^ ^
 ^^^^ ^^ ^^^^^

   Are you saying that a Shuttle crash would spread debris over an area
   a mile long? That hardly seems likely.

>> the Shuttle pilot could point his ship into the Indian River or the
>> marshes out west.

>Unless, of course, they lose power...

>Jonathan H.

   Hmm... good point.
   By the way, does anyone know if the Shuttle has destruct charges on the
   orbiter itself? I know the SRBs and ET do, what about the orbiter?
   If a Shuttle lost power and ground-zero was Orlando, could NASA blow up
   the Shuttle out over the Gulf? What about DCX in same situtation?

   (I know, I know... 'same situation can't happen with DCX'. Accidents
    happen, though. Concorde upper rudders fall off, DC-9 tailcones fall
    off, a DC-10 *engine* fell off, *two* 747 engines fell off, Challenger
    went kablooey, etc. etc. ad infinitum.)

   -Brian

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

Date: 29 Nov 92 00:30:10 GMT
From: Brian Stuart Thorn <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

>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.

>Gary


   Tread very carefully here, Gary. I'm as big a supporter of the Space
   Shuttle as anyone, but I do remember a Space Shuttle 'malfunction'
   a few years back which screwed the heck out of three deep space
   mission launch windows. One mission was delayed for three years (Galileo),
   one for four years (Ulysses), and a third had to fly a longer trajectory
   to get there after leaving ahead of schedule (Magellan).

   Let's not throw stones at expendables when Martin just launched Mars
   Observer within it's original window, while the Shuttle missed all of
   it's deep space windows.

   -Brian

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

Date: 29 Nov 92 00:30:45 GMT
From: Brian Stuart Thorn <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

>>If the same failures happen to DCX then all they need do is shut down the
>>engines which did start, find and fix the problem, and fly again. This will
>>result in RL-10's with one less malfunction and a more reliable system.
>
>They're at 10,000 feet, closing fast with the ground, and half their
>engines don't start (that's what happened in the recent failures). So
>they just stop the others, get out and fix the problem, and proceed
>to land? I don't think so. I think they'll smear all over the landscape
>before they even have time to realize they have a problem. A failure
>on the pad is one thing. A failure coming down is something altogether
>different.

>Gary

Uh, Gary... the RL-10s in Atlas-Centaur don't ignite until Centaur does,
which is after Atlas seperation, about six minutes and several hundred
thousand feet above the ground. That's alot more than 10,000 ft.

-Brian

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

Date: 28 Nov 92 23:30:13 GMT
From: Henry Spencer <[e-mail]>
Subject: Want info: sharp gun/launcher
Newsgroups: sci.space

In article <[e-mail]> d40937@aiken (Jean Yves Desbiens) writes:
>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...

Perhaps because you haven't been paying attention? :-)

Various gun-launch systems, this being one of them, have been in
small-scale development for quite a while.  This one I particularly
remember, because it got a feature article in Aviation Week & Space
Technology not too long ago, the 15 Sept issue I think.

I'd actually back Hertzberg's ram accelerator or one of the various
electromagnetic catapults over a straight light-gas gun, and a laser
launcher beats any of them by a mile, but that's personal preference
rather than doubt that the light-gas gun will work.

There are *lots* of ways of drastically cutting launch costs that look
good and have been demonstrated on a small scale, everything from
better chemical rockets to laser launchers.  The problem is not basic
feasibility, but development funding.

Incidentally, "deadly or not" is rather silly; light-gas guns are too
unwieldy to make very useful weapons.  A launch truck with a Scud on
it is a better weapon.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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End of Space Digest Volume 15 : Issue 469
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