Topic: Deorbiting versus reboosting space stations
Beau08 Member
Posts: 159 From: Peoria, AZ United States Registered: Aug 2011
posted 01-15-2012 07:02 PM
I know the Mir and Skylab space stations returned to Earth and burned up in the atmosphere, and even talk about the demise of the International Space Station, but why?
I know gravity eventually decays the orbit but is there no effective way to boost stations back into higher orbits to remain in orbit? Or do the governments choose to let them go due to the costs?
Max Q Member
Posts: 399 From: Whyalla South Australia Registered: Mar 2007
posted 01-16-2012 07:21 PM
Were there any images or video taken of the light show that would have been the Mir reentry?
SpaceAholic Member
Posts: 4437 From: Sierra Vista, Arizona Registered: Nov 1999
posted 01-16-2012 07:35 PM
MIR was re-boosted until obsolescence...
Robert Pearlman Editor
Posts: 42988 From: Houston, TX Registered: Nov 1999
posted 01-16-2012 08:43 PM
quote:Originally posted by Max Q: Were there any images or video taken of the light show that would have been the Mir reentry?
Mir's reentry was filmed and photographed from Fiji and from the air (including a chartered flight that sold seats prior to the well publicized deorbit).
Max Q Member
Posts: 399 From: Whyalla South Australia Registered: Mar 2007
posted 01-18-2012 03:08 AM
Thanks mate was an incredible sight.
garymilgrom Member
Posts: 1966 From: Atlanta, GA Registered: Feb 2007
posted 01-18-2012 06:11 AM
To the original question - the shuttle could and did boost the ISS. Does anyone know if the current automated transfer vehicles or SpaceX's Dragon capsule have similar capabilities?
Or does the ISS have fuel/thrusters to do this itself?
Robert Pearlman Editor
Posts: 42988 From: Houston, TX Registered: Nov 1999
posted 01-18-2012 09:08 AM
The International Space Station can and does reboost itself using the engines on the Zvezda service module.
The ISS did this as recently as Jan. 13 to avoid a conjunction with a piece of debris, but it also covered the need for a planned reboost a week later to put the station at the proper altitude for the arrival of Progress M-14M later this month.
Visiting vehicles, such as Progress, ATV and HTV deliver fuel to replenish the station's supply. The vehicles can and have been used to perform the reboosts, too.
But to the original question, it is not so much an issue of capability as it is one of purpose.
Mir, for example, was in such disarray at the time of its deorbit that its components were at the verge of degrading beyond the point of usefulness. All equipment has a certified on-orbit lifetime; beyond that, their reliability cannot be trusted.
This is why Soyuz can only be docked at the station for six months. Much longer and some of its components (primarily its fuel lines) exceed their certified on-orbit lifetime and cannot be used safely.
There are other factors why parking old spacecraft in high orbits is generally inadvisable but if the vehicle isn't going to be of much use to anyone in the future, then the purpose of doing so becomes questionable.
kr4mula Member
Posts: 642 From: Cinci, OH Registered: Mar 2006
posted 01-18-2012 12:43 PM
And with Skylab, the design precluded any practical means of refueling its propulsion system, thus giving it a finite lifespan.
That's not to say some creative solution couldn't have been devised, like the plans to use the shuttle to boost it. I heard somewhere that MSFC designed it that way purposefully so as to ensure it was a temporary station and would not interfere with future plans for a permanent space station after the shuttle was up and running 100 times a year at $10/pound.
Jay Chladek Member
Posts: 2272 From: Bellevue, NE, USA Registered: Aug 2007
posted 01-18-2012 03:26 PM
Other things that can preclude reboosting involve never really being able to get it up high enough to keep the orbit stable for a really long period and potentially reboosting it too high for future visiting spacecraft to potentially dock with it.
In the case of the Salyuts, Mir and the ISS, they have to work within the limits of how high a Soyuz or Progress craft can orbit to achieve a docking. Reboosting a station higher than those orbits will help lessen the decay, but if a future craft can't dock with it, there isn't much of a point.
In Skylab's case, it was put in a rather high orbit by LEO standards of I believe about 270 miles up. Only thing that had orbited higher at that point had been the Gemini craft that had used the Agena to boost to a 700 mile apogee. But still, when the atmosphere heated up beyond expectations and caused excessive air drag, even Skylab came back to Earth sooner than was expected.
If we are talking about putting something in a parking orbit in a stored state, LEO is not the place to do it, given the junk that is up there these days. A bit of the debris the ISS has to worry about comes from the Chinese ASAT test and it will likely be a number of years yet before that particular debris problem drops. The 500 mile up orbit has debris from two satellites colliding with one another and those will be fouling up that orbit for many years yet. If a piece of debris were to impact a deactivated station, it could increase the problem quite a bit for something else on similar orbits if no active debris avoidance manuevers take place while it is in storage.
So, de-orbiting once a space station gets beyond its certified on orbit life with no real ability to extend it becomes really the only viable option. But, things can be extended. The Russians were able to extend Mir's mission beyond the 10 year certified life of its core (with some problems) and the ISS has a few added pieces of equipment to allow for more extensive on-orbit repair capability than what could be done on Mir. But eventually, solar cells lose their electrical generating capacity, fuel tanks begin to degrade, etc... So the time eventually comes to pull the plug as the cost of continued operations becomes too great compared to starting with a new vehicle.
posted 01-15-2012 07:02 PM
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