Question General Spaceflight Q&A

[Mantis]

I noticed something for the first time after watching Endeavour land at the conclusion of STS-134. There appeared to be some sort of flame/hot exhaust gas radiating from the aft fusilage in the area near where the tail fin meets the OMS pods. I am guessing that it's exhaust venting from the APUs but it was the first time that I'd ever actually seen flame there - granted any flame would not likely be visible in daylight but I can't recall ever seeing that before on a night landing either. Am I correct that it was related to the APUs?

You can see it quite clearly in the image on the page below:

http://www.space.com/11839-space-shuttle-endeavour-sts134-final-landing.html

 

[garyw]

Yes, it's the APU exhaust. It's normally invisible but with night landings you can see it. It also really shows up on the Infra red!!

 

[diogom]

Yes, it's the APUs.

 

[Urwumpe]

Yes, that is the APU exhaust.

 

[Mantis]

Yes, it's the APU exhaust. It's normally invisible but with night landings you can see it. It also really shows up on the Infra red!!

I'll say! When I saw that infrared footage, my first throught was that there was a fire back there. I seem to recall that they did indeed once have a fire back there on Columbia.

Edit: It was STS-9, the Spacelab One mission flown by Columbia. Two of the three APUs caught fire just before landing. It was caused by a hydrazine leak.

 

[Wishbone]

It is 3 days (at least) and no updates at NASA on ISS Daily reports. Is it a sign of vacation season for PA folks?

 

[DanM]

What did the astronauts wear under their ACES? It looks like blue Underarmor.

 

[ky]

Their flight suits.

 

[IronRain]

How is the attitude controlled of the station? And I don't mean like hardware but actually who controls it. The astronauts/cosmonauts aboard the station or ground controllers?

 

[Wishbone]

Commands can be issued from onboard the station, and from both MCCs. AFAIR early on (before CMGs were installed) attitude control could be transferred to the Shuttle if docked.

 

[diogom]

Just wondering, how "fast" is the internet connection in the ISS?

 

[ky]

Just wondering, how "fast" is the internet connection in the ISS?

Internet browsing is done through a Citrix Remote Desktop connection to a computer at JSC in Houston, it's not that easy to quantify exactly how fast it'd be if you were up there.

The internet access is provided through the Crew Support LAN on the ISS - this is connected to the ground using the Ku-band service on NASA's Tracking and Data Relay Satellite System. This is capable of 25 megabits upstream (to space) and 300 megabits downstream bandwidth, although the service is shared with other NASA and Department of Defense spacecraft.

Because the TDRSS satellites are in geosynchronous orbit, the round-trip time to and from the ISS is about 500ms

Also,how long could the ISS stay in orbit without a crew?

 

[tblaxland]

Also,how long could the ISS stay in orbit without a crew?

It depends on:

1. How much warning they have to prepare the vehicle before de-crewing; and
2. What consumables are on board; and
3. The nature of the condition that required de-crewing and associated repairs/spares that may be required.

There are no hard answers but there is some interesting reading on the topic here: http://www.spaceref.com/news/viewsr.html?pid=22471

 

[Eagle1Division]

Opening Payload Bay Doors?...

I remember reading somewhere that the shuttle doesn't open it's bay doors soon after MECO, that it waits a good while first. I know it's vague, but if it's true, why? Wouldn't opening the payload bay doors be one of the first things done on-orbit, to get rid of the system heat of the hydraulics, EPS, APU, OMS and MPS from the climb to orbit and OMS burns?

...Maybe, is it because they want to ensure all systems are working before they open the doors?

Shuttle Reference Manual didn't even mention the opening of the Payload bay doors as one of the post-MECO ops.

 

[Turbo]

Pretty sure they open the doors after OMS-2. MECO is a good 30 minutes before OMS-2

I could be wrong but thats how I thought it was.

Edit: This is from the Nasa Space flight website for STS-135


“Main Engine Cutoff (MECO) occurred at 189/15:37:28 GMT (00/00:08:24 MET). The External Tank (ET) separated from the Orbiter at 189/15:37:49 GMT (00/00:08:45 MET). A nominal OMS-2 maneuver was performed at 189/16:06:49.1 GMT (00/00:37:45 MET). The maneuver was 64.8 sec in duration,” added the MER report.
“The payload bay doors were opened at 189/17:03:20 GMT (00/01:34:16 MET). The Ku-Band antenna was deployed and the self-test was completed with satisfactory results.”

 

[Eagle1Division]

Errr are you talking about SSU or real Space Shuttles? :blink:

Definitely the Real space shuttle...

Pretty sure they open the doors after OMS-2. MECO is a good 30 minutes before OMS-2

I could be wrong but thats how I thought it was.

Edit: This is from the Nasa Space flight website for STS-135


“Main Engine Cutoff (MECO) occurred at 189/15:37:28 GMT (00/00:08:24 MET). The External Tank (ET) separated from the Orbiter at 189/15:37:49 GMT (00/00:08:45 MET). A nominal OMS-2 maneuver was performed at 189/16:06:49.1 GMT (00/00:37:45 MET). The maneuver was 64.8 sec in duration,” added the MER report.
“The payload bay doors were opened at 189/17:03:20 GMT (00/01:34:16 MET). The Ku-Band antenna was deployed and the self-test was completed with satisfactory results.”

Okay, thanks so I know what I heard was right. I remember it was from a somewhat reliable source.

About 3 minutes less than a full hour after the OMS-2 burn! So what's the delay for? Seems like opening the doors would be one of the first priorities: to get the radiators working :blink:

 

[agentgonzo]

Definitely the Real space shuttle...



Okay, thanks so I know what I heard was right. I remember it was from a somewhat reliable source.

About 3 minutes less than a full hour after the OMS-2 burn! So what's the delay for? Seems like opening the doors would be one of the first priorities: to get the radiators working :blink:

I'm just guessing here but checklists in spaceflight aren't exactly short. They'll need to verify that the OMS-2 burn was done successfully and get confirmation from the ground that their orbit has sufficiently changed such that they are in an orbital trajectory. The last thing that you want to do is open your PLB doors and then find that you're suborbital and in 45 minutes you'll be hitting the atmosphere again.

 

[Wishbone]

Yup, that's for the AOA (abort once around) option to be viable. Speaking from memory of generic flight rules.

 

[agentgonzo]

Yup, that's for the AOA (abort once around) option to be viable. Speaking from memory of generic flight rules.

As an aside, I remember reading that AOA was massively unlikely to ever happen. The difference in velocity between a TAL (Transatlantic abort) and ATO (abort to orbit) which AOA lives in was something like half a second of main engine thrust.

 

[Mantis]

As an aside, I remember reading that AOA was massively unlikely to ever happen. The difference in velocity between a TAL (Transatlantic abort) and ATO (abort to orbit) which AOA lives in was something like half a second of main engine thrust.

I would assume though that AOA would be used after successfully achieving orbit if they discovered some dire failure of the orbiter during those post-insertion checklists - a failure of multiple fuel cells or some other potentially catestrophic event that would mandate immediate termination of the flight.