Question Hubble repair mission

[fresh squid]

I was watching a Canadian news program about space junk and related hazards. A gentleman who I respect as a space and science authority, made a comment that I just couldn't believe. He stated that the space shuttle
would manouver to an attitude that would position the heat shield in a forward facing position. He said this would protect the hubble telescope and astronauts from space debris. I cant imagine that being true. If it is, how would that help? I'd like your thoughts on this. Thanks.

 

[insane_alien]

i would actually want that bit facing backwards as the heat shield is fragile. not to mention space junk is more likely to come in from the side.

 

[simonpro]

I'm not overly familiar (or interested) in shuttle operations, but I'd imagine that this is true. The risk of a catastrophic debris collision is substantially higher in the Hubble orbital altitude than in that occupied by the ISS, partiuclarly after the Cosmos/Iridium incident.

I was, however, under the impression that the safest way for the shuttle to fly w.r.t debris hazard mitigation was with the engines facing along the velocity vector.

 

[RisingFury]

I would rather protect the crew and Hubble, because there's an extra space shuttle standing by to save them.

 

[Andy44]

Sounds to me like it's about protecting the astronauts during the EVA. A ding in the heatshield isn't quite as big an emergency as taking a projectile through the suit (and the pink meaty stuff inside the suit).

 

[fresh squid]

I'm not overly familiar (or interested) in shuttle operations, but I'd imagine that this is true. The risk of a catastrophic debris collision is substantially higher in the Hubble orbital altitude than in that occupied by the ISS, partiuclarly after the Cosmos/Iridium incident.

I was, however, under the impression that the safest way for the shuttle to fly w.r.t debris hazard mitigation was with the engines facing along the velocity vector.

I understand what your saying. I just dont see how the shuttles attitude could make a difference in safety. Isnt the shuttle at risk from debris in every direction? Does Nasa believe its a good way to increase safety margins?

 

[Andy44]

You're at more risk from debris in the direction in which you're moving. That's where the stuff with the highest relative velocity will come from.

 

[fresh squid]

O.k. I found this "Furthermore, the STS-125 mission profile will see Atlantis fly in an RCC protection attitude. ‘The Orbiter preferred attitude of -ZLV will be maintained throughout the on orbit mission phase,’ notes the SIB presentation. ‘This attitude minimizes the risk of MMOD impact to vehicle RCC.’"

Anybody know what a -zlv attitude looks like?

---------- Post added at 01:25 PM ---------- Previous post was at 12:53 PM ----------

Found more stuff. ""So you'll see with our attitude that we'll typically put the shuttle main engines toward the velocity vector (in the direction of travel). It protects the windows and the payload bay and the Freon loops and the RCC (nose cap and wing leading edge panels). So they have optimized the attitude timeline as much as they can for this mission. And we'll do our inspections, so we will know by the end of the mission if anything is required to go repair or not."

That makes more sense to me. Bloody canadian news and their so call science/space correspondant. Bob Mcdonalds gunna get an earfull. If I can get a hold of his e-mail.

Tjhanks for your help guys.

 

[simonpro]

I understand what your saying. I just dont see how the shuttles attitude could make a difference in safety. Isnt the shuttle at risk from debris in every direction? Does Nasa believe its a good way to increase safety margins?

As Andy says, the worst threat comes from things moving in the opposite direction to you, so it's best to point whatever is strongest/most expendable in that direction.

O.k. I found this "Furthermore, the STS-125 mission profile will see Atlantis fly in an RCC protection attitude. ‘The Orbiter preferred attitude of -ZLV will be maintained throughout the on orbit mission phase,’ notes the SIB presentation. ‘This attitude minimizes the risk of MMOD impact to vehicle RCC.’"

Anybody know what a -zlv attitude looks like?

It is the attitude I talked about earlier: The engines face along the velocity vector. Normally the payload bay would be oriented downwards (which is called either -xvv or +xvv I forget), but that might not be the case with hubble, it's a delicate thing when it comes to thermal control.


(edit) According to the microgravity experiment handbook, it's -zlv -xvv. Makes sense now I think about it, you'd want the positive x-axis pointing towards the cockpit.

 

[garyw]

Where is daves when you need him?

I believe that -xvv is payload bay down.

 

[Urwumpe]

I believe that -xvv is payload bay down.

No. -X in direction of the Velocity Vector means, the Shuttle flies backwards.

The payload bay is pointed downward by having -Z in the direction of the Local Vertical. Both vectors together are enough to orient the shuttle in the local velocity/local horizon coordinate system.

 

[fresh squid]

No. -X in direction of the Velocity Vector means, the Shuttle flies backwards.

The payload bay is pointed downward by having -Z in the direction of the Local Vertical. Both vectors together are enough to orient the shuttle in the local velocity/local horizon coordinate system.

So that would mean saying the shuttles attitude is -zlv would be kind of meaning less without the other vector? I'm getting a little lost here. Sorry.