[FPSPACE] praise for Foton/YES2 tether deorbit experiment

[John Locker]

You can watch the launch , live at

http://www.viewontv.com/esa/2007-09_foton-m3/

1100 GMT today ( Friday )


John


----- Original Message ----- 
From: "Jim Oberg" <jeoberg at comcast.net>
To: <fpspace at friends-partners.org>
Sent: Thursday, September 13, 2007 10:04 PM
Subject: [FPSPACE] praise for Foton/YES2 tether deorbit experiment


This tether de-orbit project is really cool,
and NASA should be ashamed of not trying
it themselves.

If used to help deorbit shuttles at the end of
their missions, it could have saved a hundred
tons of fuel this decade, and thus have cut the
number of necessary cargo-carrying launches
by three or four -- saving billions of dollars.

But the chance of embarrassment was just too
great, they probably figured.

So they let the kids give it a shot -- and European kids,
too. Cowardly and closed-minded attitude -- not a good
sign for our future in space.

Jim O

September 13, 2007 // Satellite to test special deliveries from space -

Student-led experiment would use tether system to drop 'Fotino' to Earth

http://www.msnbc.msn.com/id/20759120/

By James Oberg, NBC News space analyst // Special to MSNBC

   Russia's Foton science satellite will include an innovative space 
transportation experiment that is testing a theoretically cheaper method of 
returning small cargo from the international space station - and it's been 
designed and developed by a team of students organized by the European Space 
Agency.

   The approach is to use a space tether as a transportation mechanism, a 
concept so risky and revolutionary that existing space agencies have for 
years been afraid of even trying it out for fear of an embarrassing failure.

   The Young Engineers Satellite 2, or YES2 for short, is piggybacking into 
orbit aboard a Russian science satellite named Foton-M3, due for launch at 7 
a.m. ET Friday. The Foton satellite had two major advantages - some extra 
space for a hitchhiker, and a low orbit around Earth (about 155 miles, or 
250 kilometers). As a result, the ticket was pretty cheap.

   The low orbit is critical because the YES2 objective is to demonstrate 
the ability to fling a small landing capsule down into the atmosphere 
without the use of rockets at all. Instead, the tiny 12-pound (5.5-kilogram) 
heat-shielded sphere, nicknamed "Fotino," will be lowered from the Foton-M3 
to the end of a 19-mile-long (30-kilometer-long) fishline-thin tether (the 
reel is called "Floyd"), and then released.

   It will still be in orbit, of course. It won't just fall straight down to 
the ground.  But it will be headed home, all the same.

   Tethered space objects follow some bizarre rules of thumb: For example, 
suppose you have two masses that are connected by a tether of any given 
length, with one positioned above the other. If the tether is cut, the two 
masses enter new orbital paths. One gets higher, and one gets lower. These 
paths will still share a tangent at the orbital location where the cut 
occurred. But half an orbit after separation, the orbits will be seven times 
as far apart as when they were tethered. That factor of seven is based on 
theory - and it has been observed in reality when space tethers have been 
cut in the past.

   This happens because of physics and the laws of motion. The tether-joined 
system was orbiting as if all the mass were concentrated at some point along 
the tether. Just how far along the tether depends on the relative masses of 
the two objects. Since the velocity required to remain in a circular orbit 
decreases as altitude increases, the higher of the two objects is actually 
going a tad faster than a single object would if it were maintaining that 
same altitude. The lower object, meanwhile, follows its circular path slower 
than a solo payload would speed along to stay at the same altitude. The 
tethered lower object remains at its altitude only due to a small lift force 
from the tug on the tether.

   Cut that tether - and that is exactly what the YES2 experiment intends to 
do - and the lower object slips closer to Earth. How much it slips depends 
on how long the tether was.

   Say the original separation is 30 kilometers, and the tethered system is 
orbiting about 250 kilometers high. This means that after separating, the 
smaller capsule will wind up in an orbit with a low point of 250 minus 7 
times 30, or 40 kilometers (25 miles). That orbit grazes too deeply into the 
upper atmosphere to survive, and the payload will decelerate from air drag 
and then fall to Earth. This is exactly the plan for Foton's hitchhiker.

   The deployment will only take a few hours, and the 0.4-mm-thick nylon 
tether (19 miles of it weighs only 11 pounds) will also hit the atmosphere, 
to burn up. So the odds of ground observers seeing it in the sky are slim. 
It will pass over distant regions of Earth at dawn and dusk, the only 
intervals when it can be seen from the ground.

   In the most famous previous case of a cut tether, on the STS-75 shuttle 
mission in 1995, the tethered object was above the shuttle. When the line 
parted, by accident, it was flung into a higher orbit, in obedience to the 
factor-of-seven rule of thumb. There it remained for weeks, visible to 
ground observers as an eerie thin line marching vertically across the dusk 
skies.

   If all goes well for this experiment, future sighting opportunities may 
occur. If the concept works, it will become routine. Small tethered mail 
from space (failed equipment, medical specimens, high-value crystals, even 
personal letters) will get flung back into the atmosphere. Small science 
satellites will get flung into higher orbits. All the more reason to keep 
your eyes on this bold experiment.

   James Oberg, space analyst for NBC News, spent 22 years at NASA's Johnson 
Space Center as a Mission Control operator and an orbital designer. His 
tasks for NASA included the development of shuttle crew procedures for 
tether deployment and retrieval.

© 2007 MSNBC Interactive

Photo:      The YES2 experiment, which looks like a big red ball with an 
apparatus

      attached to the bottom, is lowered onto the larger Foton-M3 science

      satellite during preparations for launch from Russia's Baikonur 
Cosmodrome

      in Kazakhstan.
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