@S1-A.ARPA,@MIT-MC:king@Kestrel (05/02/85)
From: king@Kestrel.ARPA
_________________________________
>Date: Wed, 1 May 85 08:00:19 pdt
To: space-network-source@mit-mc.ARPA
From: pbear!peterb
Subject: Re: Paper planes in orbit
Gateway: mordor
Eugene,
Another idea is the feasibility of a paper airplane making it through
reentry. I wonder if anybody has given thought to this as a
recreation idea.
I think it would since it would have such a large surface area to weight
ratio, and that as a mechanical system is massively overdamped in terms of
stability.
So next time some one is out there on an EVA, cluth one of the paper
airplanes in a glove before leaving and let it fly.
Peter Barada
ima!pbear!peterb
ihnp4!inmet!pbear!peterb
------------------------------
It would not have a larger surface-to-weight ratio than the typical
grain of sand or dust that makes the typical meteor shower. Also, why
would it reenter?
I doubt NASA would approve an EVA after reentry burn!
Dickpeterb@pbear.UUCP (05/08/85)
Dick, I'm sorry, I should have stated that when someone was on an EVA, take the paper airplane and THROW it toward the ground and against the orbit. I think (don't have a simulator handy) that this would cause the paper airplane to leave orbit and start a reentry. As the density of the air increases, the paper airplane would(should) stabilze itself and slow down at a fast enough rate (since it's drag/weight is quite high) to prevent it from burning up when it hits the heavier atmosphere. The only problem I can see is how longit would take to reach a stabilized position. Peter Barada ima!pbear!peterb ihnp4!inmet!pbear!peterb
eugene@ames.UUCP (Eugene Miya) (05/08/85)
At the Ames Research Center, we have about two dozen wind tunnels used to
test a variety of conditions. They range in different air velocities,
pressures, and other conditions. Recently in Science, the editor made a
some what bogus statement that computers have replaced wind tunnels.
You may have seen in recent postings that there is debate about where
money is spent in NASA [say: not on the Space Shuttle or not on the Space
Station]. My immediate supervisor calls Ames "part of the little A in
NASA" meaning "Aeronautics." We are poorly funded by comparison to the
Shuttle or Space Station although the tiles were developed here [not the
glue!] and we sometimes live off the perpheral edges of the Shuttle and
Station. This situation tends to worry some people here. What does this
have to do with airplanes?
Many months ago, the Associate Director of NASA, Hans Mark, stopped by here.
He noted the above concern and he pointed out that we use wind tunnels
as test beds to reentry design. He suggested that we start to consider
the Space Station as the next platform (testbed) from which to start
scale models reentering the earth's atmosphere (rather than a wind tunnel).
Our 'arm" will be the space station, and while the planes won't be made of
paper, this idea is under consideration.
Second note: Re: stuck in space. There are films from the Skylab days
showing swimming motions in the air without the benefit of pushing off
walls or objects. It's slow, but you get there.
--eugene miya
NASA Ames Research Center
{hplabs,ihnp4,dual,hao,decwrl,allegra}!ames!aurora!eugene
@ames-vmsb.ARPA:emiya@jup.DECNET@S1-A.ARPA:host.MIT-MC.ARPA (05/10/85)
From: Ross Finlayson <rsf@Pescadero> It seems to me that you would have to throw the paper airplane awfully hard in order for the resulting velocity (vector) to produce a trajectory that reenters the Earth's atmosphere. Otherwise even the mildest burst of the shuttle's attitude jets might cause reentry! Don't forget how large an orbiting shuttle's velocity vector is relative to the Earth. Ross.
fred@mnetor.UUCP (Fred Williams) (05/13/85)
In article <3000002@pbear.UUCP> peterb@pbear.UUCP writes: > > > >Dick, > >I'm sorry, I should have stated that when someone was on an EVA, take >the paper airplane and THROW it toward the ground and against the orbit. >I think (don't have a simulator handy) that this would cause the paper >airplane to leave orbit and start a reentry. As the density of the air >increases, the paper airplane would(should) stabilze itself and slow down >at a fast enough rate (since it's drag/weight is quite high) to prevent it >from burning up when it hits the heavier atmosphere. The only problem >I can see is how longit would take to reach a stabilized position. > >Peter Barada >ima!pbear!peterb >ihnp4!inmet!pbear!peterb From a practical standpoint, the astronaut would have to have an awefully good arm. Depending on the orbit, the paper plane would need a velocity of several thousand miles per hour with respect to the spacecraft. I can't see the plane being thrown faster than 20 or 30 mph. considering that the thrower would be in a space suit. Even if you postulate a mechanical throwing device, it would probably destroy a paper plane, ( I think certainly, but I won't go overboard). So what would have to be done is go into re-entry orbit and eject the paper plane by some means. NOW! *Just how do you intend to observe what happens?* Cheers, Fred Williams
peterb@pbear.UUCP (05/13/85)
Ross,
Remember the mass of the orbiter also. the mildest burst would barely change
the velocity vector of the orbiter. On the other hand a peper airplane's
weight is measured in grams, and it would be quite easy to impart a velocity
of tens of meters per second to a paper airplane by using a slingshot. even
throwing one by a good pitcher would imaprt about 20 m/s to the airplane.
Peter Barada
{ihnp4!inmet | harvard!ima}!pbear!peterbbrent@phoenix.UUCP (Brent P. Callaghan) (05/13/85)
I can imagine a couple of problems with paper airplane
reentry via an EVA hand launch:
1) Surely an encumbered astronaut couldn't impart nearly
enough delta V to the airplane to cause it to reenter.
Wouldn't it just fall into an orbit a few hundred
feet lower ? Perhaps a rubber slingshot would be more
effective.
2) Observing yon reentering paper airplane would be next
to impossible. An embedded thin wire along the keel
could be used as a dipole transponder perhaps, but
measuring its attitude etc would be out of the question.
We're really not up to avionics for paper airplanes yet.
I have a great idea for a skydiver/stuntman: do an EVA
in all the NASA garb. Use the mobility unit to provide
deorbit delta V then discard. At entry interface, before the
heat becomes too much for the suit, deploy a drogue chute and
make a prolonged, low temperature reentry. It may take a full
orbit to keep temps within limits. Skydive down to a few
thousand feet and deploy a ram air parachute.
Pretty good stunt huh ????
--
Made in New Zealand --> Brent Callaghan
AT&T Information Systems, Lincroft, NJ
{ihnp4|mtuxo|pegasus}!phoenix!brent
(201) 576-3475peterb@pbear.UUCP (05/14/85)
Fred,
If you want to observe it, make it out of steel and use ground radar.
As for needing thousands of MPH difference to inject it into reentry,
look at skylab. It came down on drag alone. I am not implying a shuttle
rentry orbit, just a reentry. A meter per second against the orbit would
cause the airplane to drop into a lower orbit. If you applied about 10G
using a slingshot, I think you could easily acheive reentry insertion,
but the reentry would take quite a number of orbits until drag from the
atmosphere would pull it in for good.
Anybody out there have the equations handy (I don't have my physics book
at work) I would like to run up a simulation of this. Mail it and comments
to me
Peter Barada
{ihnp4!inmet | harvard!ima}!pbear!peterblwall@sdcrdcf.UUCP (Larry Wall) (05/15/85)
In article <581@mnetor.UUCP> fred@mnetor.UUCP (Fred Williams) writes: > So what would have to be done is go into re-entry orbit and eject >the paper plane by some means. > NOW! *Just how do you intend to observe what happens?* Write your address on it, and attach a postage stamp. And hope it doesn't land in someone's swimming pool. Larry Wall {allegra,burdvax,cbosgd,hplabs,ihnp4,sdcsvax}!sdcrdcf!lwall
eder@ssc-vax.UUCP (Dani Eder) (05/15/85)
> > > >I'm sorry, I should have stated that when someone was on an EVA, take > >the paper airplane and THROW it toward the ground and against the orbit. > >Peter Barada > From a practical standpoint, the astronaut would have to have an > awefully good arm. Depending on the orbit, the paper plane would > need a velocity of several thousand miles per hour with respect > to the spacecraft. I can't see the plane being thrown faster than > 20 or 30 mph. considering that the thrower would be in a space suit. > Even if you postulate a mechanical throwing device, it would probably > destroy a paper plane, ( I think certainly, but I won't go overboard). Let us assume the Orbiter is at 150 Mautical Miles. Your astronaut throws the airplane at 20 mph or 10 meters/second aft. Aft is defined as opposite your orbital motion. The airplane will now have a perigee of 140 Nautical Miles and an apogee of 150 Nautical Miles. A piece of 20-lb bond 8.5x11 inches weighs .01 lb. When folded into a paper airplane and flying stably it has a cross section of 0.5 inches square. This gives it a ballistic coefficient (weight/area) of 3 lbs/ft^2. It will decay from orbit in about 40 days. If the paper airplane has a blunt nose (0.1 foot radius), then the peak heating on re-entry will be 70 BTU/ft^2/sec (795 kW/m^2). This means the peak temperature, assuming the paper is black, will be 1900 Kelvin (2973 F). Dani Eder / ssc-vax!eder / Boeing Company
@S1-A.ARPA,@MIT-MC:dsmith%hp-mars.csnet@csnet-relay.arpa (05/17/85)
From: David Smith <dsmith%hplabs.csnet@csnet-relay.arpa> Deorbit delta-V is not very great for low earth orbit. The shuttle takes off and gets into an orbit that would reenter over the Indian ocean. Then it drops its tank and fires the OMS engines to put it into a stable orbit. This OMS burn is worth about 300 feet per second, or 200 mph.
fred@mnetor.UUCP (Fred Williams) (05/17/85)
In article <3000006@pbear.UUCP> peterb@pbear.UUCP writes: >If you want to observe it, make it out of steel and use ground radar. > Well I did think we were talking about a "paper airplane". If you want to make one out of steel, why not put tiles on it too and call I had understood that the question was: "Would the paper burn before the aerodynamic pressures slowed the plane sufficiently to allow a non-desrtructive re-entry?" If we use steel, what would be the point? I would only be interested in finding out whether or not the low cross-sectional density of a paper plane would allow it to be slowed up sufficiently before heating. A steel plane would surely burn unless protected in some way, or unless possibly it were decelerated to zero velocity with respect to the ground and dropped straight down only under its own weight. Then I imagine it would depend on the initial height. it a "space shuttle" or something like that. >As for needing thousands of MPH difference to inject it into reentry, >look at skylab. It came down on drag alone. I am not implying a shuttle >rentry orbit, just a reentry. A meter per second against the orbit would >cause the airplane to drop into a lower orbit. If you applied about 10G >using a slingshot, I think you could easily acheive reentry insertion, >but the reentry would take quite a number of orbits until drag from the >atmosphere would pull it in for good. > Please understand, I don't dispute that an object in orbit would eventually fall to earth. But from a practical standpoint I would hate to have to wait around for a relatively stable orbit to decay. Also, I would not recommend a shuttle "eva" activity in an orbit that was so close to a re-entry that an astronaut could throw an object into re-entry. No, the fact that the reactionary force would "throw" the astronaut into a higher orbit does not alter my opinion! >Anybody out there have the equations handy (I don't have my physics book >at work) I would like to run up a simulation of this. Mail it and comments >to me > >Peter Barada >{ihnp4!inmet | harvard!ima}!pbear!peterb Now, this idea of simulation seems to have merit! I was about to suggest that a computer simulation could give you all the answers and allow you to vary the conditions and run repeated cases to your heart's content at a very small fraction of the cost. Sorry, I used to work on aero-dynamic simulations of artillery shells, but that was years ago, and I don't have any materials from that job. It is quite a complicated procedure. To people in general; I promise to *try* not to post anything further on this topic. I know some of you must be getting tired of it by now. Thanks for your patience and the absence of flames! Cheers, Fred Williams
peterb@pbear.UUCP (05/20/85)
Dani,
Do you have pointers to the equations for orbit decay, and heat-reentry?
I can beleive the 40 day orbit decay, but 1500 deg F reentry heat???
I can beleive it for the shuttle, it has so much FRIGGIN mass. But as
you stated, a paper airplane weighs ~ .01 pound. So I think its
deacceleration would be quite high, so I just can't see it streaking
throught the atmosphere at speeds fast enought to make that much heat.
(If it did, it wouldn't even burn up, it would blow up as the paper
disintegrated into itty bitty bits.)
Peter Barada
{ihnp4!inmet|{harvard|cca}!ima}!pbear!peterbfreeman@spar.UUCP (Jay Freeman) (05/22/85)
/* libation to line-eater */ In article <1975@sdcrdcf.UUCP> lwall@sdcrdcf.UUCP (Larry Wall) writes: >Write your address on it, and attach a postage stamp. And hope it doesn't >land in someone's swimming pool. > With all the fuss about stability augmentation for the shuttle, I doubt that the fact that a paper airplane is airplane-shaped would have much to do with its chances for surviving reentry. But how about just tossing out a bunch of stamped, self-addressed postcards and seeing whether any of them ever came back? -- -- Jay Reynolds Freeman (Schlumberger Palo Alto Research) (canonical disclaimer)