STS-125 Hubble Space Telescope Servicing Mission 4

[lavalamp]

If anyone wants to watch the Atlantis shuttle launch live, here's a link to do that:
http://www.msnbc.msn.com/id/21134540...86841#22886841

There's not long before left before lift off now, as I write the countdown is holding at -9 mins.

Launch planned for just before 6:02 pm UTC, 2:02 pm EDT.

[lavalamp]

Countdown has resumed with 9 mins to go before launch.

[lavalamp]

Aaaaaand launched and on its way. Showing replays now.

It's gonna catch up with the HST on wednesday, maybe they'll broadcast that too.

[ewmayer]

Hope all works as planned with the upgrades - last chance to give Hubble some more working years.

I'm especially interested to see what the new wide-filed camera WFC3 can do - supposedly its capabilities, especially in the infrared, are vastly greatly than its legendary predecessor, WFPC2.

One of the astronauts on the present servicing mission, Megan something-or-other, is a graduate of one of the local high schools in my area.

[xilman]

Originally Posted by ewmayer

I'm especially interested to see what the new wide-filed camera ...

They didn't grind it down as much as the primary mirror?


Paul

[ewmayer]

Originally Posted by xilman

They didn't grind it down as much as the primary mirror?


Paul

LOL ... I have a peculiar case of finger dyslexia with respect to certain common words - typing "filed" when I intend "field" is the most common of these. No matter how many times I type the word, 80% of the time when I'm not deliberately slowing my typing down, it comes out "filed". Quantum filed theory ... Filed of Dreams ... Strawberry Fileds Forever, that sort of thing.

Problem is, the dyslexic variant doesn't get flagged by most spellcheckers.

[retina]

Originally Posted by lavalamp

If anyone wants to watch the Atlantis shuttle launch live, here's a link to do that:
http://www.msnbc.msn.com/id/21134540...86841#22886841

Evilly speaking, I am only interested to watch a launch if something goes wrong, else all the launches start to look the same. Actually, I am kind of evilly hoping that the long talked about "rescue mission" has to be launched. Presumably everyone will survive but it would be a fabulous spectacle. Books and movies recounting it would be abundant.

Oh boy, I am gonna get in trouble for this post. Some people like to think that talking about doom somehow increases the likelihood of it happening.

[lavalamp]

A rescue attempt might very well happen during this mission, from what I understand NASA is a little uncertain about the aged nitrogen and helium tanks aboard Atlantis, and they were kept at 80% pressure as late as possible before being pumped up to 100% for launch.

[Uncwilly]

Originally Posted by lavalamp

A rescue attempt might very well happen during this mission, from what I understand NASA is a little uncertain about the aged nitrogen and helium tanks aboard Atlantis, and they were kept at 80% pressure as late as possible before being pumped up to 100% for launch.

That would make it more likely a recovery flight. The plan is to have the rescue ship at T-3days and hold. IIRC it is at T-7days now. If it is N2 for cabin pressure alone, there would be issues running the ship down to 5 psi and only O2. Think Apollo 13.

[lavalamp]

It sounds a little more serious than simply running out of Nitrogen to maintain full atmospheric pressure:

Originally Posted by http://www.space.com/news/ft_070604_aging_orbiters.html

Shuttle orbiters are equipped with 24 helium and nitrogen gas tanks that pressurize the shuttle's main propulsion system, orbital maneuvering engines and nose-and-tail steering thrusters.

The spherical tanks provide pressure needed to push rocket propellants into shuttle engines and thrusters at very specific rates required to keep the spaceship on its proper course. Some of the propellants are highly volatile and ignite on contact.

Ranging in diameter from 19 to 40 inches, the tanks have lightweight titanium or steel shells wrapped with the same type of fabric used to make bulletproof vests -- Kevlar -- or carbon graphite. They hold helium and nitrogen gas at extremely high pressures (up to 4,600 pounds per square inch) and are extraordinarily dangerous.

Would nitrogen for cabin pressure even need a tank? I mean it's not like it's being used up. In any case, if all nitrogen were removed, wouldn't the pressure be closer to 3 PSI? Or are you saying they'd pump more O2 in to raise it a little? I think the space suits used in EVAs are only run at 3 PSI and pure O2.

[Uncwilly]

Originally Posted by lavalamp

Would nitrogen for cabin pressure even need a tank? I mean it's not like it's being used up. In any case, if all nitrogen were removed, wouldn't the pressure be closer to 3 PSI? Or are you saying they'd pump more O2 in to raise it a little? I think the space suits used in EVAs are only run at 3 PSI and pure O2.

I know a fellow that programmed a cpu (a hardened 80186) involved in the atmospheric control system for the ISS (back before the I). N2 does infact get leaked out, very slowly on the ISS. But, back to the shuttle. During the EVA's the airlock is cycled, N2 wasted. The air lock is refilled, N2 added. Lather, rinse, repeat 4-5 space walks. Prior to space walk ops, the ~14.7psi cabin atmospheric pressure at launch is vented down to ~10, more N2 wasted.

I'll stick by my pressure assumption for O2 when there is no N2. Your EVA suit pressure is right (in makes the suit softer).

Regarding the thruster pressure tanks. There are tanks in the rear of the craft, back by the OMS and SSME's. These work with the rear thrusters. There are also tanks in forecabin (near the nose). As long as the cabin is not damaged by an explosion, the steering should not be an insurmountable issue.