For the planned service mission to the hubble, NASA has a second shuttle readied to launch as a rescue vehicle should the first shuttle be damaged by orbital debris near the hubble.
Why is the shuttle more likely to be damaged by debris near the hubble and not the ISS or on other missions?
Best Answer.
[Note, I have previously asked this question in other forums. A friend of mine thought the contributors here might like the challenge.]
The following is a quote:
"In addition to the usual risks that accompany launch and landing, [in going to the shuttle] the Atlantis crew faces an estimated 1-in-185 chance that a micrometeoroid or a piece of space junk will inflict catastrophic damage to their craft." http://www.redorbit.com/news/space/1562129/nasa_readies_endeavor_as_hubble_mission_backup/index.html
Why would there be a greater chance of micrometeors and space junk near the hubble?
Here is a picture of some damage to the hubble: http://www.treehugger.com/space-junk-damage-hubble.jpg
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4 responses so far ↓
1 SpazzyMcGee // Sep 29, 2008
Could be that the shuttle's are just old and decrepit and NASA wants to be able to get the crew back should another fragment of foam damage the heat shielding again. However that would apply to every mission not just Hubble. Maybe they are on a strict deadline to get all the missions in before the Shuttles' decommissioning and they want another shuttle ready to go should Hubble service mission get botched or run into technical difficulties.
Long story short, I don't really know.
*edit*
OK, "old and decrepit" is an exaggeration, but NASA scientists have said that extending the usage of the space shuttles past 2010 will greatly increase the failure rate. I think its safe to assume time is catching up with them.
2 The Real Clavius // Sep 29, 2008
A Hubble servicing mission does not expose the shuttle to greater risk of damage to its heat shield. In terms of launch and orbital injection, the chances of damage are just as great for that kind of mission as for any other.
The problem is that a suitable post-ascent damage inspection of the orbiter cannot occur until the orbiter is on station. At that point the clock is running on its consumables such as oxygen, water, maneuvering fuel, electrical power, and food. So any damage discovered has to be remedied during that consumables window. The crew has nowhere else to go. They cannot land, and they cannot fly to the ISS (too much fuel required).
But in an ISS rendezvous mission, the crew has the option to remain aboard the ISS essentially indefinitely if a plan to rescue them or repair the damaged orbiter cannot be executed within the orbiter's consumable window. The readiness of a second orbiter is to prepare to fly a rescue mission within the first orbiter's consumables window in case the first orbiter is rendered unable to land by any ascent damage.
So the risk is not of greater damage due to mission destination, but of the hotel contingency plan in ISS missions that mitigates the consequence of any ascent damage.
EDIT 1:
BTW, the shuttles are not "old and decrepit." Each orbiter still has about 75% of its design lifetime (100 missions) left in it. The STS system simply cannot be operated safely and economically based on our evolved parameters for manned space flight. The accidents to Columbia and Challenger occurred not because the orbiters were old, but because they were being operated unsafely.
EDIT 2:
You seem to be stuck on the notion that figures cited for this mission are valid for this mission only. The 185:1 odds are for ANY shuttle mission, not just for the HST servicing mission. It's only being discussed in that context because that's what the next mission is for.
Imagine a game where you flip a coin every time you get to an intersection: if you flip heads you turn right, if you flip tails, you turn left. So you're cruising down Las Vegas Blvd and someone asks what the chances are of going left on Tropicana Avenue are. The answer is 50 percent, not because it has anything to do with Las Vegas or casinos, but because the odds of a particular coin-toss outcome are always 50%. It doesn't matter whether you do the experiment in Las Vegas or Houston, Texas. You might TALK about it in the context of one or the other of those cities, but where you are doesn't matter to the odds of the problem.
3 nuscorpii223 // Sep 29, 2008
The Space Shuttle in order to reach the Hubble has to ascend to nearly the maximum altitude orbit it can reach, and still have enough fuel on-board to return home. That means there is no way for it to reach the International Space Station, and even if they did reach it, there is no way to bring all the crew home at one time. That is why they have a second Space Shuttle on standby to act as a rescue vehicle in case something went wrong with the first. There is a concentration of space junk between 300 and 350 miles above the Earth because there’s a huge number of active and defunct spacecraft there and the rocket stages that brought them there. So there may be a greater risk of a collision in orbit, but any big pieces that could threaten the Shuttle would be detected from the ground and the Shuttle steered around them. Frankly, it would seem to me NASA should have always had another vehicle ready to rescue the crew if something went wrong while in orbit. There will never really be a way to rescue a crew in trouble during ascent or re-entry, but at least if they can get into orbit so a rescue craft can rendezvous with them, lives will be spared and space will become open to more and more people in more and more careers.
4 quantumclaustrophobe // Sep 29, 2008
I think the chance of a meteor strike is about even anywhere you are in space; The shuttle’s been hit at least 3 times that I know of, including one on it’s windshield during a mission in 1999.
The true danger is that on a trip to Hubble, there’s no space station to use as a port in case of a damaged spacecraft. If the shuttle is damaged on launch (like Columbia several years ago), they can remain at the station while a rescue vehicle is prepared. But a trip to Hubble means they’ll need to be rescued before the Shuttle’s supplies run out.
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