Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT_ZIP/spacedig/V16_2/V16NO221.ZIP/V16NO221

Internet Message Format | 1993-07-13 | 32KB

Date: Wed, 24 Feb 93 05:20:57
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V16 #221
To: Space Digest Readers
Precedence: bulk


Space Digest                Wed, 24 Feb 93       Volume 16 : Issue 221

Today's Topics:
                      A response from Anonymous
            Bell Rocket Belt and WASP (was Re: Rocketeer)
                             F-1 history
                          Funny name for HST
                  Getting people into Space Program!
                         Henry Spencer stamps
          How many RPM's around his own axle can human take?
              I'm really embarrassed to ask this but...
                    Mars Rescue Mission, what if!
                      Medicine/EMS/SAR in Space.
                  Nobody cares about Fred? (3 msgs)
                          Refueling in orbit
       Reliable Source says Freedom Dead, Freedom II to be dev
                              Rocketeer
        Wouldn't an earth to moon shuttle be better than fred?

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

Date: 23 Feb 93 03:54:12 GMT
From: Philip Young <[e-mail]>
Subject: A response from Anonymous
Newsgroups: news.admin.policy,alt.privacy,comp.org.eff.talk,sci.space,sci.astro

Dear anonymous, why are you victimizing people who are interested in
astronomy and other things space-related with irrelevancies, factual and
logical errors, and tastelessness?  Having announced your presence with
the subtlety of an outbreak of bubonic plague, I'm sure interested
parties would be more than willing to follow you to alt.sophistry.  Your
continued unassisted ejaculations in these particular groups demonstrate
that your concerns are more to do with ego than astronomy or philosophy.

--
Philip R. Young
Data General Australia Pty. Ltd.


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

Date: 22 Feb 93 20:52:06 -0600
From: Bill Higgins-- Beam Jockey <[e-mail]>
Subject: Bell Rocket Belt and WASP (was Re: Rocketeer)
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Joe Cain) writes:
>     I wanted to illustrate something simple about rocketry to my
> planetary geology class [...]

Doesn't it sound like it would be fun to have Joe for a teacher? (-:

>     I thought I might consider the olde Buck Rogers or Rocketeer
> back packs and let them compute how much fuel would have to be
> expended to keep a 100 kg payload hovering.

Ohboyohboy, an excuse to recycle one of my old postings...  I wrote the
following for sci.military last year when the subject came up.

==================
Jo Baute ([e-mail]) writes:

>I've got a question about the Jetpacks, like the one they showed
>during the 1984 Olympics in LA.

I know a lot about this. Jetpacks were something I studied when
preparing my slide lecture on flying cars ("Doorman, Call Me an
Aircar!") a number of years ago.

First, references.  Look at *The History of Rocket Technology; Essays
on Research, Development, and Utility*, edited by Eugene M. Emme,
Wayne State University Press, 1964.  There's an excellent essay in
there, "The Man-Rocket" by Robert D. Roach, Jr.  It covers the origins
and history of the Bell Rocket Belt.  Yes, it really was inspired by
Buck Rogers.

More recently, there was an article in *Air and Space* in June/July
1987, "Leapin' Rockets!" by Tom Huntington, which covered the Bell
story and also told a lot about Nelson Tyler, a California camera
specialist who built a copy of the BRB.  Just a
few months ago, *Final Frontier* had a first-person article by the guy
who first flew the BRB, Harold Graham. (*He* mentions Commando Cody
movies...)  I thought I had the issue here in my briefcase, but it
doesn't seem to be present.  It's the one with the International Space
Year as the cover story.

>How do those pilots keep level instead of tumbling forward ?

The Bell Rocket Belt was the brainchild of an engineer named Wendell
Moore.  The question of stability was hotly debated around the Bell
Aircraft coffeepot.  In 1958 Moore constructed a test rig where
nitrogen gas was fed through a hose to nozzles at approximately
shoulder height, looking something like this:

     pilot
     ||||
      oo
     (__)
   // >< \\
  //      \\ <--nozzles
  ^        ^
     ====
     |  |
     |  |
     [][] <--- Landing gear
               (size 11E oxfords)

The operator was tethered for safety. Roach tells us that engineers
who thought the rocket pack would be unstable oscillated, and
optimistic engineers found no difficulty in controlling the rig.
Makes a good folk tale, anyway.

Bell got an Army contract to develop the real thing, a 125-pound
device powered by a throttleable rocket motor.  The motor burned
hydrogen peroxide monopropellant and gave up to 280 pounds of thrust.
First untethered flight was 20 April 1961.  Endurance was very
limited-- 21 seconds of flight-- and, as any computer nerd who's
played "Lunar Lander" knows, you'd better reserve enough propellant to
get you back down gently.

Hey, look, here's the spec sheet.  I haven't looked at this file in a
while.

Propellant weight    47 lb
Empty weight         83 lb
Throttleable thrust  0-300 lb   (your pilot better not weigh over 188!)
Max range            866 ft
Altitude             80+ ft
Maximum speed        60+ mph
Reliablility:        100% in more than 3000 flights

Development continued through the Sixties on rocket chairs and rocket
pogo sticks in attempts to increase endurance and utility.  The
original Belt was used as a PR device and lent its glamor to all sorts
of movies, TV shows, and commercials.

As [e-mail] (John Sloan) writes,

>Baby boomers will recall seeing this model used in the TV Series _Lost
>in Space_ and in one of the early James Bond movies (_Thunderball_ I
>think) with Sean Connery.

Mark Brown ([e-mail]) also mentioned Colonel Keds (Keds
were sneakers, in the days before "running shoes.") commercials.  The
Man from Glad (plastic bags) had a crack at the BRB, too.

Dave Barton ([e-mail]) also brought up

>the WASP (Williams Aerial Survey Platform) which had a jet engine on
>the bottom; the single occupant essentially stood on the fuel tank.

Williams International, in Walled Lake, Michigan, makes little fanjet

engines for cruise missiles, which were ideal for one-man jet belts.
Bell worked with them on a jet belt with 7-minute endurance, which
first flew on 7 April 1969.

Later Williams developed the WASP, later renamed the "X-JET" for some
reason, which looked like a pilot standing in a garbage can.  The
600-pound turbofan was mounted in front of the pilot, and the WASP
could stay airborne for 30 minutes, reach speeds of 60 mph, and land
in a four-square-foot area.  This is from the info Williams sent me in
1987... I don't know where the project stands today.  It was a
contract with the Army Tank Automotive Command.

It's late and I'm tired. Think I'll skip the Hoppicopter, the Piasecki
AirGeep, and the amazing Goodyear Inflatobird.

Oh, did I mention that I *also* have a slideshow on the nuclear
airplane? (-:

Bill Higgins, Beam Jockey         | "I'm gonna keep on writing songs
Fermilab                          | until I write the song
Bitnet:      [e-mail]  | that makes the guys in Detroit
Internet:  [e-mail]  | who draw the cars
SPAN/Hepnet:      43011::HIGGINS  | put tailfins on 'em again."
                                            --John Prine

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

Date: Sat, 20 Feb 1993 23:21:49 GMT
From: Henry Spencer <[e-mail]>
Subject: F-1 history
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Gary Hughes - VMS Development) writes:
>Random F-1 factoid... apparently the application used to justify the F-1
>project when it was under USAF was that it was needed to build ballistic
>suborbital troop carriers.

Actually, there wasn't any particular mission for it.  (This is something
I meant to mention in my history posting.)  Believe it or not, there was
a time when agencies actually invested money in long-lead technology that
they were pretty sure they were going to need but weren't sure what for.
The USAF was simply sure that if things went on as they were going, they
were going to need big rockets, and it was time to start developing an
engine for them, since engines typically take longer than airframes.

One of the worst things that has happened to spaceflight in the last
25 years or so has been the near-total lack of funding for technology
work not immediately tied to specific applications.  The trouble is that
this quickly becomes a vicious circle, because nobody wants to bet his
precious application on not-yet-available technology.  This is why the
West has never tried to build an SSTO, even though there is wide consensus
that it's possible and could open a new era.

I suspect the troop-carrier story is confusion with the Army program that
eventually became the Saturn I.  The USAF wasn't interested in troop
carriers!
--
C++ is the best example of second-system| Henry Spencer @ U of Toronto Zoology
effect since OS/360.                    |  [e-mail]  utzoo!henry

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

Date: 20 Feb 93 11:09:15 EST
From: [e-mail]
Subject: Funny name for HST
Newsgroups: sci.space

In article <[e-mail]>, kjenks@gothamcity writes:
>                             This is the highest
>non-classified Shuttle flight I can recall.        [^^^^ HST repair flight]

The HST deployment flight was probably higher, since HST has no provisions for
reboosting itself, and it likely has decayed some since then.  I don't have the
numbers around, but I recall that the Solar Max repair mission was high for a
shuttle as well.

--
Chris Jones    [e-mail]

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

Date: Mon, 22 Feb 93 19:22:20 PST
From: Brian Stuart Thorn <[e-mail]>
Subject: Getting people into Space Program!
Newsgroups: sci.space

>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 the
m
>went high enough to earn the pilot astronauts wings (most did not, I believe -
-
>if the mission was a "speed" rather than an "altitude" mission, it stayed low)

>Not every high altitude flight took a new astronaut up.  Going out on a limb,
I
>bet the shuttle has made more international (i.e. non-US citizens) than the
>X-15 made in total.

   There were 99 X-15 missions, far fewer that qualified as spaceflight.
   158 men and women have flown aboard the Space Shuttle. A great many
   of them have flown many times. 14 foreign nationals (I didn't
   say "citizens", happy?) have flown aboard the Shuttle.

   So Shuttle is far, far ahead of X-15.

-------------------------------------------------------------------------
                                     "Who knows... all this might just be
Brian S. Thorn                     an elaborate simulation running inside
[e-mail]        a little device sitting on someone's table."
                                      -Captain Picard, 'Ship in a Bottle'
-------------------------------------------------------------------------

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

Date: Sat, 20 Feb 1993 22:39:04 GMT
From: Henry Spencer <[e-mail]>
Subject: Henry Spencer stamps
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:
>: To be honest, I have no idea what Henry actually looks like, so if he was
>: on those stamps, I wouldn't know anyway :-)
>
>One of the interesting things of meeting net.people in person is how
>different they look from my pre-conceived notions.  I picture Henry as
>a college professor in his forties, with slightly graying hair and
>smallish wire-rim glasses (used only for reading, of course)...

Well, not quite right, although it's a first approximation.  I think
there's still a picture of me in the UUNET face-saver archive, although
it's a few years old.
--
C++ is the best example of second-system| Henry Spencer @ U of Toronto Zoology
effect since OS/360.                    |  [e-mail]  utzoo!henry

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

Date: Sat, 20 Feb 1993 19:47:39 GMT
From: Frank Crary <[e-mail]>
Subject: How many RPM's around his own axle can human take?
Newsgroups: sci.space,sci.med

In article <[e-mail]> [e-mail] (Joni Jarvenkyla) writes:
>How many RPM's around his own axle can a human take?

>Let's take two cases: a human is sitting on a round table, under which
>is an electric motor, and then the same but standing on it?

>I need this information to designing an amusement park -type of thing,
>which will only be for "real fun" as opposed to the very lame apparates
>found in amusement parks. Of course I will finally test these on myself,
>but I needed practical guidelines along which I should be able to make
>safe tests.

I don't think sitting versus standing is a major issue. As I understand
it, the two main factors are motion of the head and time to adjust.
One major problem is the corriolous(sp?) force caused by the rotation.
They effect the motion of fluids in the inner ear and can do very
odd things to one's sense of balance. (In an extreme way: Motion
sickness.) However, this force is only present when
something is rotating _and_ moving on it's own. If someone's
head is held motionless, he wouldn't suffer from this effect. (He
probably shouldn't have his head _across_ the certer of rotation
either... then the centrifugal forces would be pulling the fluids
in the inner ear in different directions, with bad results...)
In such a case, the limits of human tolerance would probably be the
centrifugal force pushing him outward. No one should have a
problem with three g (~30m/s^2) as long as they have something to
hold on to or a seatbelt. Since

a = (rpm*3.14159/60)^2*r           (where r is the distance from
                                    the certer of rotation)

rmp^2*r < 12,000

Since you said "on a table", I assume the person will be within
a few meters of the certer of rotation, so as much as 70 rpm
would be reasonable.

However, if the person is going to move around (or even turn his
head), a _much_ slower rotation is required. Exactly how low
would depend on the individual and how long he has to get used
to it. (NASA studies suggest that people can adjust to up to
3rpm within a few days). For an ammusement park, there wouldn't
be any time to adjust. I don't know how slowly you would have to
turn, but I suspect it would be under 1rmp.

                                                     Frank Crary
                                                     CU Boulder

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

Date: 20 Feb 93 23:40:51 GMT
From: "Brian D. Schieber" <[e-mail]>
Subject: I'm really embarrassed to ask this but...
Newsgroups: sci.space

Hi,
 I have this friend who conned me into finding out how her
friend can name a star after her boyfriend.  I TOLD YOU I
was embarrassed.  Anyway, I read somewhere that one can do
this but I no longer know how.  Could someone please send me
a message on how its done?   If you want to flame me I have
no defense expect to plead mercy.

Sorry,
 Brian

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^ Brian D. Schieber                     ^
^ [e-mail]            ^
^---------------------------------------^
^ UNIX SEAPAK Project                   ^
^ NASA/Goddard Space Flight Center      ^
^ Laboratory for Hydrospheric Processes ^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

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

Date: Sat, 20 Feb 1993 23:34:31 GMT
From: Henry Spencer <[e-mail]>
Subject: Mars Rescue Mission, what if!
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Pat) writes:
>Tha astronauts attempt a precision landing at factory 1.
>If they make it. great  put the other one  somewhere within 400
>miles of their current base...
>If they miss by a large amount,  they land the second factory
>at their location.

Actually, the way Zubrin put it was (roughly) "if they land nowhere near
the first return vehicle, we land the second one near them -- and since
it lands automatically, it should land where we *want* it to land!".
--
C++ is the best example of second-system| Henry Spencer @ U of Toronto Zoology
effect since OS/360.                    |  [e-mail]  utzoo!henry

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

Date: 22 Feb 93 20:59:28 -0600
From: Bill Higgins-- Beam Jockey <[e-mail]>
Subject: Medicine/EMS/SAR in Space.
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] writes:
> Question how do you do an IV (Interveneous) in space? What about other gravity

"Intravenous."

> related procedures?
> Im an EMT (Emergency Medical Technician for those who don't know the
> abbreviations). And I would love to practice my sills in space..

"Skills."

> EMS (Emergency Medical Service), Search and Rescue (SAR) in Space what an
> interesting thought.
> Im sure those who are there will create their own procedures and protocols.

"I'm."

I'm glad to know you're not in some critical profession where
attention to detail is important, Michael.  Such as secretary.

Bill Higgins
Sometime Technical Writer and Editor of Procedures and Protocols
Fermi National Accelerator Laboratory
[e-mail]

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

Date: Mon, 22 Feb 93 19:15:12 PST
From: Brian Stuart Thorn <[e-mail]>
Subject: Nobody cares about Fred?
Newsgroups: sci.space

>In article <[e-mail]> [e-mail] (Brian Stuart Thorn) w
r
>ites:
>
>>    I'm confused again, Allen. Why do you say that "the Hare" (the US)
>>    thinks that refueling is too dangerous?
>
>Because when I asked an engineer working logistics at the Freedom program
>office why Freedom stationkeeping thrusters wouldn't be refueled in space
>he told me it was considered too dangerous.
>
>>    refuel. The Freedom design, at least until Billary killed it, called
>>    for either refuelling or complete changeout of propulsion modules.
>
>The plan was to bring the whole mdoule back. This is far more expensive
>then refueling.
>

      Only if you assume something other that Shuttle will do the
      refueling. I'd have liked to seen a backup fueling system in
      case of Shuttle unavailability. However, since Freedom servicing
      is (was) entirely Shuttleborne, there is no difference in cost
      between a Shuttle refueling Freedom or a Shuttle replacing Freedom
      thruster modules.

      Replacement is safer, too. And since 1986, NASA has been under
      de facto orders to do things the safest way possible. If an
      astronaut were killed refueling Freedom, there'd be noises on
      Earth about why NASA didn't do a safer module swap-out. If the
      Shuttle is grounded and Freedom forced into free-drift for lack
      of fuel, there'd be noises about why NASA didn't provide for
      non-Shuttle refueling. In this no-win situation, I would opt for
      the safest method too.

-------------------------------------------------------------------------
                                     "Who knows... all this might just be
Brian S. Thorn                     an elaborate simulation running inside
[e-mail]        a little device sitting on someone's table."
                                      -Captain Picard, 'Ship in a Bottle'
-------------------------------------------------------------------------

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

Date: Mon, 22 Feb 93 19:21:38 PST
From: Brian Stuart Thorn <[e-mail]>
Subject: Nobody cares about Fred?
Newsgroups: sci.space

>This is at least the fifth time I've seen you accuse someone of accusing
>you of being a liar this week; the fact that someone doesn't believe you
>doesn't necessarily mean they think you are lying, they may just think you
>are plain incorrect.  Your persecution complex is showing.

    You have a good point about alternatives to intentional falsehoods,
    but I think there is no mistake what "less than truthful" means.

    However, I expected Allen to have a thicker skin than that, after
    all this time.

-------------------------------------------------------------------------
                                     "Who knows... all this might just be
Brian S. Thorn                     an elaborate simulation running inside
[e-mail]        a little device sitting on someone's table."
                                      -Captain Picard, 'Ship in a Bottle'
-------------------------------------------------------------------------

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

Date: Tue, 23 Feb 1993 04:16:47 GMT
From: tomas o munoz 283-4072 <[e-mail]>
Subject: Nobody cares about Fred?
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Allen W. Sherzer) writes:

|> >Ok, but what did he *mean* by that? Too dangerous to Freedom to leave
|> >years old valving and thrusters uninspected in orbit perhaps?
|>
|> No, he was very clear. He ment the risk to an astronaut re-fueling. This
|> is one byproduct of the lack of EVA we have been doing.

Again, it's not the lack of EVA, it's the fact that you don't want
hydrazine all over the EVA crew.


|> The thrusters in question are very reliable and don't need constant
|> inspection to last years.

Thrusters will stay in orbit for years at a time.  They will be inspected
and/or refurbished every time they are returned to earth.


|> >>The plan was to bring the whole mdoule back. This is far more expensive
|> >>then refueling.
|>
|> >Is it?
|>
|> Well at over $10,000 a pound for launch costs I wold say yes.

There's alot more to it than launching it - that's the easy part.


|> >Seems to me that since Shuttle is coming
|> >down anyway, it might as well return the thruster modules for easier on
|> >ground inspection, repair, and refilling.
|>
|> They rarely need this.

Rarely need what?  At ~1 prop delivery per 1 - 2 years, 2 modules per delivery, 8 modules total, each module will need to be refilled
every ~3-4 years.


|> >refueling tankage in any event.
|>
|> Maybe we don't need tankage. Maybe we use fuel from the OMS.

I don't think the OMS are big enough to fuel both orbiter and SSF.


--
========================================================================
Tom Munoz     |   [e-mail]

Thought for the day [plagiarized from someone else]:

Engineers think equations are an approximation of reality.
Physicists think reality is an approximation of the equations.
Mathematicians never make the connection.
========================================================================

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

Date: Mon, 22 Feb 93 19:14:26 PST
From: Brian Stuart Thorn <[e-mail]>
Subject: Refueling in orbit
Newsgroups: sci.space

>But what is the point if those some technologies are never used.
>I am glad ORS was done, and safer  and the MMU is refueled.
>But look at NASA's own planning.  The Now dead SSF was going to
>have no on-orbit refueling.  How is that useful?

   Why take the technology risk when you have the capability
   to do a comparatively simple "swap out" of thruster modules?

>The Centaur which could have benefitted from on-orbit refueling
>never had a test program to achieve this mission.
>What kind of bargain is it, when ORS is done, quite well from your
>description, and then not placed into the technology bed for the
>largest program in NASA history.

    Centaur is an application, but how many payloads would require
    this application? Just one: Galileo. Galileo was already way
    over budget and behind schedule without attempting a new
    technology to get the job done. Sure, a Centaur launch would
    have eliminated the antenna problem. Hindsight is 20/20.

>IT would be like Gemini testing Orbital rendevous and docking
>and Apollo saying no docking is too risky and dangerous.
>We'll use giant NOVA rockets instead.  at 100 billion dollars.

    Gemini and Agena demonstrated Earth Orbit Rendezvous as well.
    Two missions were boosted to higher orbit after docking with
    Agenas. There was consideration for this approach to get Apollo
    to the Moon. Even though Gemini showed it could be done, Apollo
    didn't do it.

>If you prove a technology and technique, use it.  if not, it's as
>bad as never having done the test.
>
>|The most expensive technology is forgotten or shelved technology. One
>|can say that the shuttle is now expensive to run and made of outdated
>|technology. Uhh,,,,yea, I guess thats right. In the same light I can
>|scoff at my neighbor and his four year old antique home computer, while
>|I hold out for more power and lower cost. But you and I should think
>|carefully about how much benefit was obtained and is still coming from
>|that old bucket while snipers sit on the sidelines with only inaccurate
>|criticism in hand. Unlike the computer case though, as Gary C. pointed
>|out, "The Shuttle is a marvelous workshop *solely* because it is the
>|*only* heavy lift workshop *flying* regularly to various orbits..."..
>
>Isn't this last statement the damnest criticism of NASA i can think of.
>20 years after apollo,  and where are we?  8 flights/year ina workshop
>whose owners are afraid of gassing your car.
>
>
>|*Someone else* may buy those computers to drive up capabilities and
>|drive down costs for you, but in the space biz, we're it. You wait, you
>|lose.
>
>  Kinda the way galileo waited?  or HST waited . or Skylab waited?
>  lots of missions wait for shuttle.

    Lots of missions are currently waiting for Titan IV/Centaur too.
    Not to mention the two payloads GD dumped in the Atlantic
    recently. Someone's waiting for Atlas, too.

>   My point was that no on-orbit cryo fueling has been tested or is
>planned to be tested.  THis is a useful technology  and would make
>lemonade from lemons.  I would suggest that you look into pushing
>this sort of research from within.

    Please note that the frequently touted Russians have now cryo
    upper stages, hence they haven't done cryo refueling in orbit,
    either.

>No doubt money is short in important areas,  but it's also poorly
>allocated in others.  NASA should return to their basic mission of
>testing technologies and advancing research and not driving a bus
>or running a business.  they aren't that good at it.

    Apparently, neither are General Dynamics or Martin-Marietta.
    These firms took over launch of their Atlas and Titan boosters.
    Launch rates and success rates have fallen since they did so.

-------------------------------------------------------------------------
                                     "Who knows... all this might just be
Brian S. Thorn                     an elaborate simulation running inside
[e-mail]        a little device sitting on someone's table."
                                      -Captain Picard, 'Ship in a Bottle'
-------------------------------------------------------------------------

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

Date: 20 Feb 1993 19:37:46 GMT
From: CLAUDIO OLIVEIRA EGALON <[e-mail]>
Subject: Reliable Source says Freedom Dead, Freedom II to be dev
Newsgroups: sci.space

Do they already have a date for deployment of SSF II???

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

Date: 23 Feb 93 05:57:15 GMT
From: Russell Mcmahon <[e-mail]>
Subject: Rocketeer
Newsgroups: sci.space

Question: What exhaust velocoties can you expect for a rocket backpack.

A:  Velocity is given by Isp x g where g is in units you are comfortable
with (m/s f/s etc) and Isp is the specific impuls of the fuel which
is effectively the thrust for one second expended when unit mass of
the fuel is burnt. Working in steam driven units (fps which seems to
still pervade rocketry) g=32 feet per second per second and Isp is usually
expressed in seconds.lbf/lbm   It is common(albeit wrong) to cancel
the lbf and the lbm and to express Isp in seconds.

Some common values are

    LOX and alcohol       about 230
    LOX and hydrocarbon   about 300
    Best solid fules      around 250
    LOX and LH2           400 to 450 (LOX and Liquid Hydrogen)

Actual results depend on chamber pressures and external pressure (and
a few dozen other minor factors). As your rocket man is presumably starting
off at ground level and not flying in space lower values will be normal
(eg 400 ish for LOX/LH2)

You could convert this to a velocity eg 32 x 400 = 12800 feet per second
but Isp gives you a nice (rough) rule of thumb as is.
Say you have a total initial mass of 300 pounds (still steam driven
units). You want to balance this with a 300 pound force so as you are
getting 400 pounds thrust per pound burnt for LOX/LH2 you need 300/400
= 0.75 pounds of fuel per second. As the fuel is consumed your weight
falls but not by too much if the man has a small backpack. For say 30
pounds of fuel he can "fly" FOR 4/3 X 30 = 40 seconds
Using a less energetic fuel (say Isp = 200) gives less time.
The units used in the James Bond movie (can't recall name) used monopropellant
 H2O2 I believe with an Isp of around 100 (or less) and a flight time
of around 20 seconds. No doubt there will be some USA based experts
on this subject.

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

Date: 23 Feb 93 03:04:56 GMT
From: Craig Meyer <[e-mail]>
Subject: Wouldn't an earth to moon shuttle be better than fred?
Newsgroups: sci.space

> Well, why should we have an Earth-moon shuttle if nobody wants to go to the
> moon (or at least, if nobody who has any money wants to go to the moon)?
>
> How do you fuel/refuel the beast?  If you aren't using aerobraking at the
> earthside, you've got on the order of 8 km/sec delta v for a round trip.
> That's on the same order of as much as it took to achieve orbit in the first
> place.  If you are doing aerobraking, the delta v goes down, but you have to
> worry about inspecting/replacing your heat shield after transfer into LEO.

I like the Leo-moon shuttle idea, myself.  The only fundamental problem I see
is that you've got gravity on the moon, which means you CAN'T do a lot of
experiments that a space station would be suited to.

I'd do it like this:

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.

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.

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End of Space Digest Volume 16 : Issue 221
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