NASASpaceFlight.com Forum

NASA Shuttle Specific Sections => Atlantis (Post STS-135, T&R) => Topic started by: John2375 on 08/22/2007 02:19 pm

Title: Beta Angle for STS-122
Post by: John2375 on 08/22/2007 02:19 pm

On the 120 thread, it's mentioned there's a beta angle cutout from Dec. 13-30th.. even if 122 launches by 12/6 won't that limit their time at the ISS?? or does it somehow not apply to this flight??

Title: Re: Beta Angle for STS-122
Post by: rdale on 08/22/2007 02:39 pm

Beta angle cutouts are based on launch date, those aren't the actual beta-problem days.

Title: Re: Beta Angle for STS-122
Post by: John2375 on 08/22/2007 03:11 pm

Oh ok - understood - thanks!!

Title: Re: Beta Angle for STS-122
Post by: USFJoseph on 08/22/2007 04:54 pm

So for a non-rocket scientist can someone explain what the beta angle is?

Title: Re: Beta Angle for STS-122
Post by: Jim on 08/22/2007 05:23 pm

Do a seach.  It been explained many times

Title: Re: Beta Angle for STS-122
Post by: USFJoseph on 08/23/2007 12:34 am

Thanks -- got a PM defining it.  Didn't see it in the acronym list (yeah I know it's not an acronym) so I posted. ;)

Title: Re: Beta Angle for STS-122
Post by: Lee Jay on 08/23/2007 02:05 am

I'm a bit confused.  If P6 gets relocated on STS-120, and then redeployed, will this not give ISS some extra power and thermal margin to help relax the Beta angle restriction?

Title: Re: Beta Angle for STS-122
Post by: Jorge on 08/23/2007 02:37 am

Quote

Lee Jay - 22/8/2007  9:05 PM

I'm a bit confused.  If P6 gets relocated on STS-120, and then redeployed, will this not give ISS some extra power and thermal margin to help relax the Beta angle restriction?

It is a thermal certification limit. The situation will likely improve but analysis must be done to establish a new limit. There is work in progress to relax the limit from 60 to 65 degrees. Relaxing the limit to 75 degrees would effectively eliminate it because ISS beta angle never exceeds 75 (51.6 inclination plus 23.4 obliquity of the ecliptic) but I don't think they'll be able to go that far.

Title: Re: Beta Angle for STS-122
Post by: Lee Jay on 08/23/2007 02:45 am

Is is a hot limit or a cold one?  I guess I would think cold and therefore I don't really understand why having the Shuttle there would hurt the situation.

Title: Re: Beta Angle for STS-122
Post by: Jorge on 08/23/2007 03:44 am

Quote

Lee Jay - 22/8/2007  9:45 PM

Is is a hot limit or a cold one?  I guess I would think cold and therefore I don't really understand why having the Shuttle there would hurt the situation.

It's a hot limit. At high beta angles, you get more orbital day and less orbital night. At beta of 70 degrees or above night time goes to zero. Any shuttle/ISS stack attitude is a bit of a thermal compromise for the radiators of both vehicles, but you can get away with it at low beta because there's enough night time for everything to cool down. It gets harder to find a good compromise at high beta. Not impossible, but not a trivial analysis either.

Title: Re: Beta Angle for STS-122
Post by: Lee Jay on 08/23/2007 01:00 pm

I see.  Thanks, Jorge.

I'd still think deployment of the P6 radiators would help the issue.

Title: RE: Beta Angle for STS-122
Post by: Analyst on 08/23/2007 01:58 pm

P6 only has one PVR needed for its own IEA. The other two radiators won't be useful/can not be connected to the cooling system/are not needed.

Analyst

Title: RE: Beta Angle for STS-122
Post by: Lee Jay on 08/23/2007 07:19 pm

Quote

Analyst - 23/8/2007  7:58 AM

P6 only has one PVR needed for its own IEA. The other two radiators won't be useful/can not be connected to the cooling system/are not needed.

Analyst

Ah...that explains it.  I though the SARJ had rotary couplings to hook up to the ammonia loops.  Now it makes sense.  Thanks.