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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."
Since I submitted the article, another report has said this morning's emergency is not a problem, and they may attempt another orbit raising burn today. There is lots of time to make a correction and the orbit is OK for now.
$#!^ happens, but why does it always have to happen to me???
This isn't a good situation, but barring future disasters I'm confident that they'll get a ship up there to boost the ISS to a level where it can be saved for many more decades.
If you want to see the graphical representation of the ISS's altitude, there's a nice chart at Heavens-above.com It's a free sign-up, and the bonus is you can find out when ISS flies over your house so you can see it or even take pictures like I do sometimes.
I had noticed just a few days ago that the orbit was at its lowest point, and was getting concerned about what they were going to do about it.
Saskboy's blog is good. 9 out of 10 dentists agree.
The first burn will be performed at 5:09pm for 705 seconds, the second at 6:33pm for 700 sec, both with 2.94 m/s delta-V each. Main purpose of the reboost is to set up proper orbit phasing for Progress 20 launch. [The burns will be performed by eight DPO-BT thrusters of Progress 19, from the #1 manifold and will be controlled in attitude by Service Module MNFD thrusters from both manifolds. The 19P burns are steered by the SM motion control & navigation system (SUDN) via the US-21 matching unit (installed in 19P on 9/13). The propulsion systems were tested successfully on 9/15.]
They got 170 seconds out of 1405 seconds or about 12% of a burn. MOSCOW, October 19 (Itar-Tass) --A cargo ship docked at the International Space Station (ISS) fired its engine Wednesday to raise the space research platform into a higher orbit but in about three minutes the engine failed and the operation was canceled.
The correction was to boost the space station more than 10 kilometers further from Earth into an orbit that was to reach 356.8 kilometers on the average.
Normally, ISS goes down by 100-150 meters daily. That's about 3-5KM a month.
Also, there are no Shuttles ready that could boost the orbit either, so the Russians are the ONLY method right now. I'm not sure how fast the Russians can send up another Progess if the one currently docked can't get the job done. This IS a serious risk to the station and crew, but it's not panic time.
That sucks, but I think someone is being a bit sensational. They have almost a year to correct this. They have a mission planned in two months, by that time it will still be at least 330km up. They have been that low before. Also, by your own link, it takes at least three weeks for the orbit to decay from 300km, I have seen others that say up to 3 months. Neither of those are "a matter of days".
Actually, the Earth's atmosphere extends out to roughly 2000 kilometers or so. Spacecraft orbiting within 2000 kilometers are slowly spiraling in, due to the the tiny amount of air resistance.
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~ |rip/\/\aster /\/\onkey
They are in LEO, Low Earth Orbit, with emphasis on Low. So yes, there is some drag from the "atmosphere".
The mistake you're making is to think there's some sort of sharp dividing line between "atmosphere" and "space". NASA defines "space" as beginning about 50 miles above the earth, but traces of atmosphere extend well above that.
Well, they have the Soyuz capsules, which were first designed in the 1960s and are currently supplying the ISS because our own shuttles keep blowing up. There was also the Mir, which was falling apart toward the end but still lasted far beyond when its original specs said it would die.
The Russians have had a lot of stuff blow up, but so have the Americans. They have also built a lot of really great technology that is in active use right now.
A better way to think about it is in terms of forces, not velocities. In order for an object to travel in a circle, there must be an inward-directed force, a centripetal force. Imagine you're swinging a ball on a string around your head. The ball travels in a circle because the string is continually applying an inward-directed force to it. For an object in orbit, this inward-directed force is gravity.
The image of the craft continually "missing" the Earth is not as useful, because the size of the Earth really isn't relevant to the question of orbit -- only its mass is. An object can orbit whenever its speed is less than the escape velocity. It's just that some orbits, unfortunately, intersect with the surface of the Earth.
Because then it would be in a higher orbit :-) Harder to reach, takes more fuel to carry heavy stuff up there, more interaction with the moon, etc. You typically want a human-occupied space station to be closer to the planet.
ISS orbit is at a compromise altitude and angle that barely allows both the Shuttle and the Soyuz to arrive with cargo. In addition the maximum altitude is limited to about 500 km due to thats the lower limit of the Van Allen radiation belts. Loss of altitude is due to the drag effects of atomic oxygen at the that altitude.
Frankly the station is a great candidate for the addition of ion thruster engines to help maintain altitude.
Every additional item of structure added to the station ( solar panels, etc) causes extra drag. At this time if the station were to case orbital adjustment it would burn up in about 1 year.
not entirely due to gravity though gravity is certainly involved.
an orbiting object has its lateral velocity balanced with gravity in such a way that its state stays steady, but atnospheric resistance takes away energy from the object causing it to spiral into lower and lower orbits (and as the orbit gets lower the resistance gets greater accelerating the process).
note: i'm known as plugwash most places but i screwd up registering that here somehow in the past and now can't register