Space & Astronomy/Space and Astronomy (October 1993).iso/pc/text/spacedig/v16_2/v16no228.txt

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Date: Fri, 26 Feb 93 05:06:24
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V16 #228
To: Space Digest Readers
Precedence: bulk


Space Digest                Fri, 26 Feb 93       Volume 16 : Issue 228

Today's Topics:
                       Aurora (rumors) (2 msgs)
               How to be a councilor at Huntsville...?
                How to power the LEO-moon space bus :)
                           Internet control
                    Mars Rescue Mission, what if!
                McElwaine disciplined! (somewhat long)
               NF-104 (was Re: kerosene/peroxide SSTO)
Reliable Source says Freedom Dead, Freedom II to be developed (2 msgs)
software engineering vs. civil engineering (wasRe: Nobody cares about Fred?)
       SSF Resupply (Was Re: Nobody cares about Fred?) (2 msgs)
                       Stars in space pictures?
                          The Future of Fred
        Wouldn't an earth to moon shuttle be better than fred?
     X-15 astronauts (was Re: Getting people into Space Program!)

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Date: 24 Feb 93 05:25:47 GMT
From: Craig Meyer <[e-mail]>
Subject: Aurora (rumors)
Newsgroups: sci.space

> When you travel faster than sound (hence the sonic booms), people on the
> ground hear the plane after it has already passed.  There are two ways
> to be stealthy.  Make yourself invisible, or go so fast that it won't
> matter :-).  A combination would work best.
>
> Go fast enough and your plane will be LONG gone by the time anyone
> (audibly) detects it.

It's not like the Aurora flies RIGHT OVER the target, anyway.  According to the
PS article, it's got this neat-o super-detailed SIDE-looking radar system.  In
other words, when the thing flies by, it could be a HUNDRED miles away and
still see YOU fine, since it's so high up and the radar system is so high-res.

It's NOT audible to the target.

CM
--
       Craig Meyer                 [e-mail]
       Indiana Academy for Science, Mathematics, and Humaities.
       Muncie, IN  47306                          317-285-7433

       Opinions expressed are mine alone, and not necessarily
       shared by the Indiana Academy.

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

Date: Wed, 24 Feb 93 14:02:15 GMT
From: Dean Adams <[e-mail]>
Subject: Aurora (rumors)
Newsgroups: sci.space

[e-mail] (Craig Meyer) writes:
 >> Go fast enough and your plane will be LONG gone by the time anyone
 >> (audibly) detects it.
 >It's not like the Aurora flies RIGHT OVER the target, anyway.

Depends on the target...

 >According to the PS article, it's got this neat-o
 >super-detailed SIDE-looking radar system.

Well, that is nothing new.  Even the original U-2 could carry a SLAR
(Side-Looking Airborne Radar) package, and the SR-71 carried the
"radar nose" with a SLAR/SAR unit on a regular basis.

 >It's NOT audible to the target.

At a 100K+ feet up, it would probably not be audible
even if it *was* right overhead.

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

Date: 24 Feb 1993 01:16:44 -0500
From: Bill <[e-mail]>
Subject: How to be a councilor at Huntsville...?
Newsgroups: sci.space

I have a friend that wants to be a councilor for the Space Camp at huntsville.
Does anyone know the proper channels to go through so she can apply?  I guess
she just wants phone numbers of people she needs to call, and she wanted me
to ask here.  E-mail replies please.

Thanx in advance,

    Bill

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

Date: 24 Feb 93 05:52:20 GMT
From: Craig Meyer <[e-mail]>
Subject: How to power the LEO-moon space bus :)
Newsgroups: sci.space

"Moon" World Book Encylclopedia:

"Moon rocks consist chiefly of minerals containing aluminum, calcium, iron,
magnesium, oxygen, silicon, and titanium.  Hydrogen, helium, and other gases
are trapped in some of the rocks."

A lot of discussion lately about how to slow down on one's way back from the
moon.

I've been wondering if, along with building materials, some sort of propellant
could be extracted from moon dirt.

Oxygen (and therefore LOX) looks easy enough.
The only thing on my list from the World Book that looks "worth
burning" is Aluminum.  Could it be burned quickly in some kind of powdered
form?

When it comes to frieght runs back and forth from LEO to the moon, NUCLEAR
PROPULSION SYSTEMS look like the way to go.  A few Uranium spheres will take
you a long way, along with a little hydrogen gas as a working fluid.  As long
as the thing never came back to earth, radiation wouldn't be nearly as
much of a problem.

In my opinion, space looks like the ideal environment for applying nuclear
power.

CM
--
       Craig Meyer                 [e-mail]
       Indiana Academy for Science, Mathematics, and Humaities.
       Muncie, IN  47306                          317-285-7435

       Opinions expressed are mine alone, and not necessarily
       shared by the Indiana Academy.

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

Date: Tue, 23 Feb 93 18:27:08 PST
From: Jason Cooper <[e-mail]>
Subject: Internet control
Newsgroups: sci.space

I have seen some postings on here that I can't seem to follow up that
talk about preserving the control we currently have over the net.  My
question to those who say this (to be answerd by e-mail) is this:  What
control?  Anybody in an unmoderated group who thinks they have _OR_
deserve control over any part of the internet has their head in the
clouds.  The Internet is all about free speech and LACK of control by any
one person, and anybody with illusions of control obviously needs to get
a lengthy checkup.

                                                        Jason Cooper

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

Date: 24 Feb 93 07:27:55 GMT
From: Henry Spencer <[e-mail]>
Subject: Mars Rescue Mission, what if!
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Phil G. Fraering) writes:
>Anyway, it's probably time to mention the best documentary for the
>layman on polar exploration: _Scott of the Antarctic_. If you can
>find it...

Actually, I'd pick Huntford's "Scott and Amundsen" (republished as
"The Last Place On Earth" to tie in with the PBS series).  For example,
Huntford was possibly the first historian to compare Scott's original
diary to the published version... and they don't agree.  The orthodox
accounts utterly fail to capture the depth of Scott's bungling.  (Case
in point.  Scott had experience with scurvy but made no attempt to
take precautions against it.  Its cause wasn't fully understood at
the time, but precautions were possible -- Amundsen took some.  It is
very likely that Scott and his party had advanced cases of scurvy,
on top of everything else.)
--
C++ is the best example of second-system| Henry Spencer @ U of Toronto Zoology
effect since OS/360.                    |  [e-mail]  utzoo!henry

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

Date: Tue, 23 Feb 93 18:18:37 PST
From: Jason Cooper <[e-mail]>
Subject: McElwaine disciplined! (somewhat long)
Newsgroups: sci.skeptic,sci.space,sci.astro,sci.space.shuttle

[e-mail] (Phil G. Fraering) writes:

> [e-mail] (Russell J. Pagenkopf) writes:
>
> >In article <[e-mail]> [e-mail] () writes:
> >>It always worries me when someone is stomped on because of what he says,
> >>even if what he says is unadulturated gibberish.  Are we so thin-skinned
> >>that we can't just ignore stuff we don't want to see?
>
> >* SOAPBOX ON *
>
> >I must agree with you Andrew.  Just because *you* (newsgroups in
> >general) don't agree with what someone has to say doesn't mean you have the
> >right to CENSOR him/her.  Yes, I agree that sometimes some of the posts can
> ...
>
> Maybe it's about time a lot of these people learned about
> a newsreader called 'nn'.

BRAVO!

                                                Jason Cooper

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

Date: 23 Feb 93 14:14:32 GMT
From: AJ Madison <[e-mail]>
Subject: NF-104 (was Re: kerosene/peroxide SSTO)
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Mary Shafer) writes:
> On Thu, 18 Feb 1993 00:22:24 GMT, [e-mail] (Henry Spencer) said:
>
> HS> In article <[e-mail]> [e-mail] (Mary Shafer) writes:
> >> NF-104 rocket-boosted aircraft flown by NASA and the USAF...
> >BG> Isn't that the one Chuck Yeager almost killed himself in? ...
> >
> >That's the one immortalized in "The Right Stuff".
> >Supposedly, that incident (Chuck taking off because he felt like it)
> >is the reason that Edwards AFB uses the system of ops numbers and
> >CONFORM...
>
> HS> Actually, the subject came up when Mitch Burnside Clapp was talking about
> HS> NF-104 peroxide experience at Making Orbit 93, and Mitch said (as best
> HS> I recall) that the movie had exaggerated the unauthorized nature of
> HS> Yeager's flight.  (I don't know details myself, but given how many other
> HS> things the movie exaggerated, I can well believe it...)
>
> Exaggerated, yes, but still true.  I suspect that it was just a last
> straw in leading to the CONFORM system.  I can tell you a number of
> stories about both real and attempted fighter theft at other bases, so
> maybe it's not too bad a system.
>

In the Book, _The_Right_Stuff_ there is no mention made whatsoever of
Yeager taking the NF-104 out unauthorized.  In fact, if I remember this
right, Yeager made two flights the day of the crash.  He made a morning
flight that was uneventful.  In the afternoon, the way it was described,
the much warmer and thinner afternoon air allowed Yeager to set a new
altitude record, and unfortunately, on the way back down, the air was so
thin at altitude, that there was insufficent aerodynamic forces to
control or stabilize the plane.  There is a long passage of, "Yeager
tried this, tried that, tried this again", something to the effect that
Chuck tried to bring the plane out of the flat spin from 102,000 to 5,000
feet and finally gave up and punched out.

HS> My understanding is that there were never any serious problems with the
HS> peroxide hardware, and the aircraft systems gave no more trouble than
HS> usual.  However, the F-104 was a notoriously unforgiving aircraft, and
HS> flying a ballistic trajectory using rocket boost wouldn't be exactly an
HS> easy mission even in a better-behaved aircraft.  It worked fairly well
HS> but called for good pilots who never let their guard down even briefly.

So this confirms that there was nothing wrong with the rocket hardware.
A case might even be made that it worked *too* well, at least for the
type of plane it was bolted to.
--
A.J. Madison                       PHONE: [phone] X383
FiberCom, Inc.                       FAX: [phone]
P.O. Box 11966                  INTERNET: [e-mail]
Roanoke, VA  24022-1966             UUCP: ...!uunet!fibercom!ajm

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

Date: 23 Feb 1993 22:30 CST
From: [e-mail]
Subject: Reliable Source says Freedom Dead, Freedom II to be developed
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Allen W. Sherzer) writes...
>In article <[e-mail]> [e-mail] writes:
>
>>The problem with this design is that the problems with EVA and on orbit
>>maintenance is magnifed tenfold. Not only do you have to do all of the
>>EVA associated with the external structure, BUT you have to do EVA to
>>install all of the internal equipment, life support..... AND then do
>>all of your testing on orbit.
>
>But Dennis, this is pretty much what NASA planned to do with Freedom
>before the micromanagers in Congress insisted on greater integration
>to minimize this problem. NASA disagreed saying on orbit instalation
>wasn't a problem.
>
>So you agree with Congress and disagree with NASA. I'm glad we find
>ourselves in agreement.
>

No there is one heck of a lot of difference in taking up SSF with more
on orbit integration (most of the construction work was to build the truss,
remember one of the large construction projects in orbit that you like)
This is what was scaled way back by having the truss built in larger
pieces on the ground and then launched in the cargo bay.  This is also the
case with the refueling that has been talked about here. They are simply
changing them out instead of doing all of the on orbit work to refuel.  In
addition, the Resupply module is also a quick changout item instead of
having astronauts work to bring new supplies in.

With an ET design you have none of the above with the added problems of
completely having to build up the interior from scratch. This is a job
that would take thousands of man hours to accomplish before real work
could even get started.  This is an order of magnitude problem Allen and not
one that would be anywhere near cost effective to solve for the first
station.

I would love to see an ET in orbit for a resource of raw materials for
future construction!

>>Then when things don't work which will happen
>>you have to have all of these contingency missions just to correct all of
>>the things you did not know about till you got there.
>
>Which is why the growth in logistics shuttle flights was called 'alarming'
>in an internal NASA briefing in early 89.
>
>  Allen
>--

That alarm was silenced during the design of station three years ago. To
bring this up now that the problem has been largely solved is meaningless.

By the way care to answer the post about sources?

I will be meeting with some sources in the next few days that are working
on plans to save about 2-5 billion dollars over the life of station in
operating costs. May not sound like much but you take a billion here
and a billion there and pretty soon it adds up to real money.

This plan will result in no changes to the overall design and will allow
the schedule for firt element launch to be maintained, which will save
uncle sugar a few billion more by not having to go back and start over. Why
not post here? Well you will find out soon enough and the decisions on
SSF are not made on Usenet.

Positive action

Dennis, University of Alabama in Huntsville

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

Date: 24 Feb 93 15:40:05 GMT
From: "Brian A.Laxson" <[e-mail]>
Subject: Reliable Source says Freedom Dead, Freedom II to be developed
Newsgroups: sci.space

In article <[e-mail]>
[e-mail] writes:
> In article <[e-mail]>, [e-mail] (Pat)
writes...
> >THe way I see it, is you get a quick volume, cheap  and NASA only has
> >to worry about the trusses and tanks and maintenance.  any experiments
> >can bring up their gear and the mission specialists can
> >install it.   If a submarine can be serviced entirely through
> >little hatches, i am sure a station could be too.
> >


    Submarines need drydocks occasionally.  A submarine also is
dealing with a different enviroment, which it is not meant to explore.
Alot of space equipment relies on being affecting by changes in the
enviroment (i.e. heat differentials to deploy antennas).  I don't think
you could get this sort of exposure and still provide thorough maintenance
through hatches.

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

Date: 23 Feb 93 17:50:02 GMT
From: Spiros Triantafyllopoulos <[e-mail]>
Subject: software engineering vs. civil engineering (wasRe: Nobody cares about Fred?)
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (fred j mccall 575-3539) writes:
>>Software engineering yahhh... Kinda like "military intelligence" hmmm?
>
>Yeah, sure.  Of course, you probably also want to say that the Tacoma
>Narrows bridge was a *software* failure, too.  So tell me again how
>there's no such thing as software engineering because it isn't
>predictable and well understood like 'real' engineering -- like, say,
>bridge design and construction . . .

Perhaps I can shed some light, having the fortune (?) of being both a
civil and a software engineer, college educated in both. (gave up
civil years ago, no $ in Greece at the time...)

One bridge collapsing while thousands of bridges stay put is not an indicator
of bridge design in general. A good bridge (or building) designer can factor
in ALL known things that will happen to the bridge. Software IS used for
the analysis phase (solid modeling, materials, simulations).

Building a bridge basically uses principles that are commonly understood,
are taught everywhere the same way (tensile strength of steel is the same
in China as in Greece...). Ditto for requirements analysis, i.e. so much
load, so much wind, etc. Soil mechanics also; materials also; And,
frankly speaking, it is *feasible* that anyone can open up a book, read
up, and design a bridge that WON'T fail. The principles are in the book,
and building requirements/regulations/material properties provide quite a
bit of safety factors built in. There may be material differences (concrete
vs. steel) but by and large no major problems exist.

Software, on the other hand, is unpredictable by nature. Ask 10 software
engineers to design the same problem and you'll get 10 drastically different
answers; software can't be proven correct; bridges can. Rarely, if ever,
bridge designers change the design or get 100 new pages of requirements...
The software world thrives on such things. And, quite interestingly,
nobody I know has ever written a book that can teach anyone how to write
software in a concise manner; If I choose a material or method to use in
a bridge, any fellow bridge engineer will see it and realize why I did
it (i.e. prestressed concrete vs. poured concrete). In software,
this is not very realistic given the complex software products people
produce.

Software is more of an 'inner' product. There are many aspects of the
software development process that can be handled thru normal
engineering procedures, but there will always be the little bit of
'art' that the individual programmer will add. There are cases that a
programmer will implement the same thing in 10 different ways
depending on mood. A bridge engineer *won't*.

If I were to compare software engineering to another field, it'd only be
architecture. Not engineering.

To give an even better quote, "Engineering is to Software Engineering what
Fluid Mechanics is to Plumbing".

Spiros
--
Spiros Triantafyllopoulos                    [e-mail]
Software Technology, Delco Electronics       [phone]
GM Hughes Electronics, Kokomo, IN 46904      [A Different Kind of Disclaimer]

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

Date: 23 Feb 1993 22:13 CST
From: [e-mail]
Subject: SSF Resupply (Was Re: Nobody cares about Fred?)
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (fred j mccall 575-3539) writes...
>In <[e-mail]> [e-mail] (Brian Stuart Thorn) writes:
>

>And if the Shuttle is grounded and the station is forced into
>free-drift for lack of replacement thruster modules (which is the same
>thing as saying that it ran out of fuel), then where are you?  It all
>comes down to just how much money and opportunity cost is a small
>incremental change in safety worth.  It is this failure at rational
>risk analysis that has earned parts of NASA the poor reputation for
>performance and cost effectiveness that they have.
>

The above is an opinion and should not be considered by the reader as
gospel.  What about Titan IV ? Admittedly Titan IV's record is not
stellar, but in the event of a problem the Air Force has 41 of them and
they could be used in the event of Shuttle stand down due to disaster.

Also the Station is primarily gravity gradient stabilized in order to
preserve the microgravity environment. There could be many methods
implemented to help reduce fuel use in case of trouble.

In addition, it is my understanding that the primary reason for the
Fuel on SSF is not for attitude control but for reboost. Now certainly
they could live without reboost for a few months or even a year or two.

Quit making mountains out of molehills. Just because you have not thought
of the solution or you have not read it in Space News or seen it on
Usnet does not mean that contingencies do not exist.

>--
>"Insisting on perfect safety is for people who don't have the balls to live
> in the real world."   -- Mary Shafer, NASA Ames Dryden
>------------------------------------------------------------------------------
>[e-mail] - I don't speak for others and they don't speak for me.


You really ought to read the above statement by Mary that you append on your
messages.

Dennis, University of Alabama in Huntsville

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

Date: Wed, 24 Feb 1993 15:26:13 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: SSF Resupply (Was Re: Nobody cares about Fred?)
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:


>>And if the Shuttle is grounded and the station is forced into
>>free-drift for lack of replacement thruster modules (which is the same
>>thing as saying that it ran out of fuel), then where are you?

>What about Titan IV ?

Well I would prefer either Atlas or maybe a Titan III. that would
save you about $100 million.

But then I forget: the only way to replace the thrusters is with
Shuttle. NASA designed it so that it can't be done with expendables.

Now if we bought the Russian docking technology and made a lot of
modifications we could.

>In addition, it is my understanding that the primary reason for the
>Fuel on SSF is not for attitude control but for reboost. Now certainly
>they could live without reboost for a few months or even a year or two.

A few months yes but not a year. About 180 days after missing a firing
(and there is one every Shuttle flight) it will re-enter.

>Quit making mountains out of molehills. Just because you have not thought
>of the solution or you have not read it in Space News or seen it on
>Usnet does not mean that contingencies do not exist.

apparently it also means they may not exist.

  Allen


--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | "A great man is one who does nothing but leaves        |
|  [e-mail]     |  nothing undone"                                       |
+----------------------111 DAYS TO FIRST FLIGHT OF DCX----------------------+

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

Date: Wed, 24 Feb 1993 12:05:59 GMT
From: Wolfram Kresse <[e-mail]>
Subject: Stars in space pictures?
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Scott Harris) writes:
> In every space picture I've ever seen, like the ones of Earth, the Moon, the
> various planets, etc., I have never seen *stars*.  Shouldn't there be millions
> of stars showing all around in space?
>

No. Stars are much too dark in comparison to the other objects to be visible.

> Scott

Wolfram

--

+-------+---------------------------------------------------------------+
|       |Wolfram Kresse * E-Mail: [e-mail]|
|  / \  +--------------------------+---------------+--------------------+
|  o o  |"Meeneemeeneemeenee"      |CU l8r, LE g8r!|
|   <   |"Yes,that's right,Tweeky."+---------------+
|  ___  +-----+----+---------------+
| /   \ | 8^) | =) |
+-------+-----+----+

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

Date: 23 Feb 1993 22:51 CST
From: [e-mail]
Subject: The Future of Fred
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] writes...
{stuff Deleted]



>
>Since the design for Freedom obviously wouldn't work, I'm not shedding any
>tears for its' demise. NASA will certainly work with the other countires
>to ensure that their modules will interface with both the new station and
>Mir II. The Canadians work may go for naught, however, but its early yet.
>

I love posts like this. Any proof of this assertation. I'm sure Panetta
would give you many golden attaboys for this.

>The rumor is that the new station will be orbital within 4 years. I would
>prefer a real station in orbit to one that will permanently be on paper.
>

Whose rumor? No one that I have spoken with thinks that. If you completely
redesign the station from scratch, which is what it is going to take in
order to cut costs as much as Panetta would like, (Unless Allen can get
DC1 in the air in less than ten years (and I hope they can!)) it will
not fly in four years. The folks at NASA are just now getting into the
meat of seeing what can be done to cut costs and still get any space
station up there. So scratch that romour

>Furthermore, even if it turns out to be a Space Winnebago, with a couple
>of foreign modules attached, we honestly could use a flight prototype for
>a followup now, rather than attempt the whole shebang with no flight
>experience. After all, most of the folks who built Skylab are long gone.
>
>

Says who? Jack Lee, who was the Project manager under Von Braun for Skylab
is now the center director. Ever wonder why Work package I is on time and
within budget? (Oops for the non Huntsville people, He is the director
of the NASA Marshall Space Flight Center).

Roy Lanier, who was one of the lead design engineers on Skylabs Electrical
power system is still at Marshall. In fact many of the folks who did
Skylab at Marshall are still on the job.  Heck the flight spare batteries
for Skylab are being used at Marshall for Space Station power system
demonstrators !!!!

So get off of it, like Jack Webb always used to say "Just the facts mam"

Dennis, University of Alabama in Huntsville

PS just to make sure you know, the batteries are in building 4487 room
C101. This is the Skylab battery room and is still in use. Too many on
here forget things like the battle for the power system that pitted
the DC power system against a 20 khz AC system. This battle was won and
is one of the unknown things done to build a good station.

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

Date: Wed, 24 Feb 1993 05:47:32 GMT
From: Dave Rickel <[e-mail]>
Subject: Wouldn't an earth to moon shuttle be better than fred?
Newsgroups: sci.space

In article <1993Feb22.220456.15572@bsu-ucs>, [e-mail] (Craig Meyer) writes:
|> I'd just launch up a big pack of SSTO's, one with the parcel, and the other
|> with auxiliary gas tanks.  Fill up the parcel SSTO with gas from the other
|> SSTO's.
|>

|> Maybe the delta v is nearly the same for launching and to-moon travelling, but
|> does that necessarily translate directly to liters of fuel?  There's no air to
|> push through up there, after all.


Hmm.  This is starting to sound like the earth rendezvous lunar mission, with
an Earth-LEO shuttle and an LEO-LTO-LO-Moon-ETO-LEO craft.  I'm not sure that
this makes sense unless you have some sort of nuclear propulsion option.

Oh well, let's plug in some rough numbers:

LEO-LTO:    3.2 km/s    (actually LEO-escape)
LTO-LO:         .7 km/s    (actually LO-escape)
LO-Moon:    2.0 km/s    (derated a bit for maneuvering)
Moon-ETO:    2.4 km/s    (escape from moon)
--------------------------
        8.3 km/s

plus an additional 3.2 km/s if you don't do aerobraking at the end for 11.5
km/s delta v.

Note that this is for an actual lunar landing; i think the original post
was for an earth orbit to lunar orbit shuttle, which of course is easier,
but possibly less useful.

Anyway, derate by an additional 10%; call it 9.1 km/s with aerobraking, 12.7
without.  Figure an exhaust velocity of 4.46 km/s (SSME in vacuum); that
gives a mass ratio of 7.7 with aerobraking, 17 without.  17 seems too high to
be practical unless you were aiming for multiple stages.  So the aerobraking
penalty might be worthwhile (note that the mass you're finally aerobraking
is only a fraction of the all-up mass--about 13%).

Hmm.  One more table, just for kicks.  This time with the mass at the end of
the maneuver as a fraction of the all-up mass:

LEO-LTO:    3.2 km/s    0.454
LTO-LO:         .7 km/s    0.382
LO-Moon:    2.0 km/s    0.234
Moon-ETO:    2.4 km/s    0.129
ETO-LEO:    3.2 km/s    0.059


Refurbishing on orbit doesn't really appear economical over reentering all
the way and refurbishing on the ground.  Either way you need to replace the
heat shield, possibly replace the lunar landing gear, refuel the RCS engines,
resupply life support, etc.  If you do it on the ground, it costs you an
additional launch (8 launches vs 7).


david rickel
[e-mail]

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

Date: Wed, 24 Feb 93 12:25:56 GMT
From: Dean Adams <[e-mail]>
Subject: X-15 astronauts (was Re: Getting people into Space Program!)
Newsgroups: sci.space

[e-mail] (Bill Higgins) writes:
 >> In article <[e-mail]> [e-mail] (Chris Jones) writes:
 >> |In article <[e-mail]>, prb@access (Pat) writes:
 >> |>Seriously.  My point was that the X-15 was qualifying astronauts
 >> |>at a rate that I think the SHuttle only passed recently.
 >> |I don't think so.  I believe there were 99 X-15 flights TOTAL.  Not all
 >> |of them went high enough to earn the pilot astronauts wings

 >I think  Chris is right on this.

Not quite... There were a TOTAL of *199* X-15 flights, over a 10 year peroid.

 >The number of X-15 pilots qualifying as astronauts (some criterion like
 >reaching an altitude greater than 80 km) was really small, like about
 >three.  Wish I had the references to check.

There were 12 pilots in total.  If you have the correct criterion,
then about 8 of them would have earned their "wings"...

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End of Space Digest Volume 16 : Issue 228
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