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ISS Orbit-Raising Attempt Fails
hpulley writes "ITAR-TASS reports that the Progress cargo ship currently docked at the ISS attempted an orbit raising burn this morning but the engine failed three minutes into the firing. Further burns are cancelled until they figure out the problem and meanwhile, the station continues to lose approximately a kilometer of altitude every week, with the rate increasing as the orbit decays. At present, the schedule says the next Progress, 20P, will be launched on December 21st, nearly 9 weeks from now. Normally the shuttle would also raise the orbit of ISS but it is not scheduled to launch until May 3rd at the earliest. Nominally the ISS orbits at 358km but if it drops to 300km, it may decay in a matter of days. It was down to 340km already on October 13th."
Nine months might sound like a long while. But consider the lead times for rockets. Can an unscheduled mission be planned, built, prepped, tested, rubberstamped and shot into orbit inside nine months?
These Russians have years of experience in the field. Heck, they had MIR for 15 years. That is, 3 times the time it was intendd to last. Sad that we as Americans can only sit and observe at least for now. Even aftr pumping billions into our space program, I will not be suuprised if things just do not work for us.
Will the same thing happen to ISS that happened to Skylab? A series of incidents (generally involving funding) that results in the space station sinking below a level that it could be lifted out.
Of course there are people in ISS, so it's perhaps a bit too early to wonder if funding would be delayed long enough for ISS to fall to Earth.
“Common sense is not so common.” — Voltaire
So why haven't they put that tether experiment on the ISS that the shuttle ran a number of years ago. Basically it was able to turn orbital motion into electricity or electicity to motion. Next trip take them up a tether and a bunch of solar cell and Fagetaboutit.
I couldn't fail to disagree with you any less.
Here's a dumb idea: Hook a long coaxial cable with a sizable mass (how about a dead satellite?) onto the ISS. Then feed electrical power through the cable (up the center, down the outer jacket) so that the vector crossproduct of the current and the earth's magnetic field act to accelerate the ISS. How much power is required to keep the orbit from decaying, i.e. can this power be reasonably supplied by the existing or an additional solar array? A scheme like this would reduce or eliminate the dependence on periodic orbit boosts by cranky Russian rockets or once-in-whenever Space Shuttle flights.
Less is more.
IANARocketScientist, and for those other readers who aren't can someone please explain:
Why don't they have ISS in a higher orbit that won't decay as fast/often? And again, pardon my ignorance, but my (un)common sense tells me if they are at a high enough orbit, it shouldn't decay as readily - too high and you have the opposite problem of drifting farther away from Earth.
In other words, rather than having to make orbit adjustments so often, isn't it possible to push it to a high enough orbit that won't require a tweak for a longer period of time?
TIA for n00b-enlightenment.
Being 'overrated' lets add more fuel to the fire :)
Those applets are nice but they both rely on constants, as if gravity never changes. There are lots of things that can change the orbit of an object, different areas of the Earth have greater pull then others (oceans don't have as much 'pull' as say continents and the Moon is a huge variable.
Atmospheric drag is another that can not be calculated as well as other variables.
Simply put, there are too many things that 'could' happen for someone to expect long term stability in an orbit. These 'orbital correction' burns are very common in any orbiting body and the closer they are to the planet the more often they are needed.
Troll: Last I heard was the the Moon is in a decaying orbit and is expected to crash into the Earth within the next 1 billion years or so =P
"Some things have to be believed to be seen." - Ralph Hodgson
However, for low mass objects this effect is very small, so we can effectivel rule it out in this case. Someone had correctly pointed out that the moon is slowly getting closer. This is due to the affect described above.
It occurs to me that station-keeping engines would be an excellent application for ion engines. They don't have the power to push the thing into orbit, but certainly they could be built with enough thrust to counter the atmospheric drag at those altitudes. While it would take a bit of effort to bring the engines up on the rockets, it would probably be more than compensated by being able to shuttle up a small load of xenon every now and then instead of all of the fuel necessary to boost it back into its original orbit.
Maybe it's just convenient to have it ride lower every now and again, but I can't imagine that the fuel saved by the lower orbit compensates for having to push it back up there again. I haven't done the math, but it's possible that ion engines would allow it to stay at a lower altitude indefinitely, since there's no danger of decay.
And while we're at it, maybe we could design these things with just a tad bit of aerodynamic considerations. Ok, I'm truly talking out my backside right now, but it's fun to think about how to avoid this kind of thing.
Wake up - the future is arriving faster than you think.
Frankly the station is a great candidate for the addition of ion thruster engines to help maintain altitude.
Not only ion thrusters, but perhaps also 3 or 4 small conventional oxygen/hydrogen rocket engines strategically placed in case the station ever needs some higher amounts of thrust or steering manuvering capability for unforseen emergencies. The extra oxygen and hydrogen stored on board for those engines could also be diverted to fuel cells for emergency power needs and the oxygen for life support. (Scotty!!! we've got a breech of the outer hull from a meteor strike and shields have failed! Divert auxilary power from the thrusters to life support now!!!). The continuous low-level ion thrust could counter the additional drag from the extra weight to maintain orbital altitude, and the other engines would be there for "just-in-case", hoping you'd never really need them.
Of course, we'd need a ship big and reliable enough to get those engines, supplies and installation crew up there to install the stuff... but I digress...
Thanks for the great explanation Moofie. ;)
The problem is that the tethers get damaged by micrometeors. A small comparison graph of the degradation rate of single and interlinked tethers can be seen near the bottom of http://www.tethers.com/Hoytether.html. IMHO, this means that other (non-tethered) means of magnetic propulsion may be worth investigating, as there is nothing unique about the tethered geometry which makes it advantageous for magnetic propusion.
Also, having a space station down as close to the Earth as is practical allows them to do lots of things that would be harder from much further out. Rememeber, we're talking 200 miles vs. 22,000 miles. Also, the ISS travels over much of the Earth each orbit, which allows it to do things over much of the Earth's surface if needed.
A geosychronous or geostationary satellite is always in approximately the same place above the Earth all the time, so if you want to do an experiment that needs to be done over Texas ... too bad. A geosynchronous or geostationary satellite is always approximately (geosynchronous satellites do move around a little bit) above the same place -- which is always on the equator. It's also a bit crowded up there already ...
I wonder if the ISS gets signifigantly more benefits of shielding from radiation up there by the Earth's magnetic field than it would if it were at 22,000 miles? It may be that going up to 22,000 miles would increase the overall radiation so much that humans couldn't live up there for an extended period of time without lots of very heavy and expensive shielding? (I don't know, it's just a guess.)
And at a mere 200 miles up, I can even whip out my 5 watt ham band handi-talkie radio and can reach the amateur repeater on the ISS. Were it 22,000 miles up, I'd need more power and bigger antennas.
There is no impending catastrophe here. There was a problem, yes, but the ISS is still many months from crashing into the Earth -- there's lots of time to get these problems fixed.