Author Topic: What's up with the pressure suit visor rules?  (Read 4628 times)

Offline spacemuppet

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What's up with the pressure suit visor rules?
« on: 02/13/2007 01:49 AM »
Why are the astronauts allowed to raise their visors and thus "depressurize" their suits so early into the ascent?  What is the point of the pressure suit if this is done?  

(on an unrelated note, I had a thread about "life aboard Orion" deleted yesterday, why would this be deleted for no reason?)

Offline Jim

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Re: What's up with the pressure suit visor rules?
« Reply #1 on: 02/13/2007 01:56 AM »
The suit are not pressurized, they only have O2 flowing through the helmet.   The suit is an escape suit that provides pressure in case of  an emergency.  

As for them raising them, they do it after the  SRB's are jettisoned.  A real sign of the astronaut office's feelings about the SRB's.  

Funny, they are still going to use these supposedly "safe" SRB's for the Ares I

Offline James Lowe1

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RE: What's up with the pressure suit visor rules?
« Reply #2 on: 02/13/2007 01:58 AM »
Threads are never deleted without a reason. The usual case is they are merged into existing threads - like this one really is a Shuttle Q&A post.

I believe your Orion thread was a question, which was answered, and you acknowledged = dead thread.

We have to keep this place tidy, so that users don't have to trawl through thousands of threads to find what they are looking through.

Offline simonbp

Re: What's up with the pressure suit visor rules?
« Reply #3 on: 02/13/2007 02:36 AM »
Quote
Jim - 12/2/2007  8:56 PM

A real sign of the astronaut office's feelings about the SRB's.  

Funny, they are still going to use these supposedly "safe" SRB's for the Ares I

Indeed; didn't the idea for using a shuttle SRB to launch a capsule come out of the astronaut office after Columbia? ;)

Simon ;)

Offline spacemuppet

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Re: What's up with the pressure suit visor rules?
« Reply #4 on: 02/13/2007 03:18 AM »
I like the idea of the butyl fuel with throttle-able "LOXidizer".  "Hybrid SRB" is what they call it I think.

Offline spaceflight101

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Re: What's up with the pressure suit visor rules?
« Reply #5 on: 02/14/2007 12:07 AM »
Quote
Jim - 12/2/2007  9:56 PM

The suit are not pressurized, they only have O2 flowing through the helmet.   The suit is an escape suit that provides pressure in case of  an emergency.  

As for them raising them, they do it after the  SRB's are jettisoned.  A real sign of the astronaut office's feelings about the SRB's.  

Funny, they are still going to use these supposedly "safe" SRB's for the Ares I

Yeah, but...since the architecture is more like Apollo's, the crew will be sitting atop the stack, not beside it as they are now, and so the risk factor decreases.

I suppose going back to LOX and kerosene isn't an option. Water-white kerosene for heaters went up to $2.70 per gallon last week!

Offline C5C6

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Re: What's up with the pressure suit visor rules?
« Reply #6 on: 02/14/2007 12:55 AM »
Quote
Jim - 12/2/2007  11:56 PM

The suit is an escape suit that provides pressure in case of  an emergency.  
in what type of emergency would the suit be useful??

Offline HailColumbia

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Re: What's up with the pressure suit visor rules?
« Reply #7 on: 02/14/2007 01:07 AM »
Quote
C5C6 - 13/2/2007  8:55 PM

Quote
Jim - 12/2/2007  11:56 PM

The suit is an escape suit that provides pressure in case of  an emergency.  
in what type of emergency would the suit be useful??

during Challenger, the crew was alive until impact with the ocean.  They were not wearing suits and loss of atmosphere rendered them unconscious. in a similar situation, if they were alert, MAYBE they could have bailed out. (they added an escape rail to the middeck for this)
I don’t think that many people believe that even with suits this scenario would be survivable.  There are a hundred other ways the shuttle can kill you, and most of the time the suit won't do much, but it at least gives you a fighting chance.    
-Steve

Offline Jim

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Re: What's up with the pressure suit visor rules?
« Reply #8 on: 02/14/2007 01:28 AM »
Quote
C5C6 - 13/2/2007  8:55 PM

Quote
Jim - 12/2/2007  11:56 PM

The suit is an escape suit that provides pressure in case of  an emergency.  
in what type of emergency would the suit be useful??

The orbiter has bailout capability while in a stable glide.  The orbiter will not survive a ditching and bail out is the only option

Offline missinglink

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Re: What's up with the pressure suit visor rules?
« Reply #9 on: 02/16/2007 08:20 PM »
Speaking of visors... why do space suits still feature a GLASS visor? It's breakable! Why not a solid metal sphere surrounding the head, and lots of tiny high-resolution cameras to give panoramic vision, or close-up magnification for detail work, or extreme telephoto for long-distance observation. If astronauts bump their heads during an EVA, they no longer risk breaking the glass!

Offline Jim

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Re: What's up with the pressure suit visor rules?
« Reply #10 on: 02/16/2007 11:40 PM »
Quote
missinglink - 16/2/2007  4:20 PM

Speaking of visors... why do space suits still feature a GLASS visor? It's breakable! Why not a solid metal sphere surrounding the head, and lots of tiny high-resolution cameras to give panoramic vision, or close-up magnification for detail work, or extreme telephoto for long-distance observation. If astronauts bump their heads during an EVA, they no longer risk breaking the glass!

It's not glass but lexan

Cameras can fail

Offline nathan.moeller

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Re: What's up with the pressure suit visor rules?
« Reply #11 on: 02/16/2007 11:46 PM »
Jim, could you give a few specs on lexan?  I'm curious to know what it is made of.  I've always wondered what would happen if an EVA crewmember were to bump his noggen on something, but it's comforting to know it's not some kind of glass.
www.astro95media.com - Lead Video & Graphics

Offline Stargazin2nite

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RE: What's up with the pressure suit visor rules?
« Reply #12 on: 02/17/2007 12:20 AM »
Lexan is pretty common stuff -- found in everything from waterbottles to aircraft windows, bullet-resistant windows, etc.  There's a good overview at Wikipedia:

http://en.wikipedia.org/wiki/Lexan

Offline dwmzmm

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Re: What's up with the pressure suit visor rules?
« Reply #13 on: 02/17/2007 12:04 PM »
Recall that the crew members of the Blackbird aircrafts (SR-71 and the seldom used fighter version YF-12A) also wore what certainly looks like
astronaut suits (Gemini/Shuttle style).  It's been said that those suits were to protect them in the event of an emergency bailout at high speeds/altitude that the Blackbirds were capable of...
Dave, NAR # 21853 SR.

Offline Rocket Nut

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Re: What's up with the pressure suit visor rules?
« Reply #14 on: 02/18/2007 12:10 PM »
Quote
dwmzmm - 17/2/2007  8:04 AM

Recall that the crew members of the Blackbird aircrafts (SR-71 and the seldom used fighter version YF-12A) also wore what certainly looks like
astronaut suits (Gemini/Shuttle style).  It's been said that those suits were to protect them in the event of an emergency bailout at high speeds/altitude that the Blackbirds were capable of...

We also used them in the RB-57F.  Primary use for us was for rapid depressurization at high altitudes.  They would also have been useful for bailout at high altitudes, although I don't think they were ever successfully used in the RB-57s.

We kept the faceplate down for the entire flight, opening them at 25,000 feet on descent.  Suits were deflated at normal cabin pressure which was around 25,000 feet at altitude.  Suits would inflate when cabin altitude reached 35,000 feet.  By the time we had descended to 25,000 feet at the end of the mission, the cabin altitude was nearer 8,000 feet.

I can still remember that within minutes fo closing that faceplate for pre-breathing, my nose would start itching...couldn't scratch my nose for the next 4-9 hours...torture.

Cheers,

Larry




Offline dwmzmm

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Re: What's up with the pressure suit visor rules?
« Reply #15 on: 02/18/2007 12:20 PM »
Quote
Rocket Nut - 18/2/2007  7:10 AM

Quote
dwmzmm - 17/2/2007  8:04 AM

Recall that the crew members of the Blackbird aircrafts (SR-71 and the seldom used fighter version YF-12A) also wore what certainly looks like
astronaut suits (Gemini/Shuttle style).  It's been said that those suits were to protect them in the event of an emergency bailout at high speeds/altitude that the Blackbirds were capable of...

We also used them in the RB-57F.  Primary use for us was for rapid depressurization at high altitudes.  They would also have been useful for bailout at high altitudes, although I don't think they were ever successfully used in the RB-57s.

We kept the faceplate down for the entire flight, opening them at 25,000 feet on descent.  Suits were deflated at normal cabin pressure which was around 25,000 feet at altitude.  Suits would inflate when cabin altitude reached 35,000 feet.  By the time we had descended to 25,000 feet at the end of the mission, the cabin altitude was nearer 8,000 feet.

I can still remember that within minutes fo closing that faceplate for pre-breathing, my nose would start itching...couldn't scratch my nose for the next 4-9 hours...torture.

Cheers,

Larry




Wow, that must have been very uncomfortable at times, Larry!  Thanks for sharing that!
Dave, NAR # 21853 SR.

Offline mkirk

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Re: What's up with the pressure suit visor rules?
« Reply #16 on: 02/19/2007 04:46 PM »
Quote
Jim - 12/2/2007  8:56 PM

The suit are not pressurized, they only have O2 flowing through the helmet.   The suit is an escape suit that provides pressure in case of  an emergency.  

As for them raising them, they do it after the  SRB's are jettisoned.  A real sign of the astronaut office's feelings about the SRB's.  

Funny, they are still going to use these supposedly "safe" SRB's for the Ares I

The issue is not really related to the SRBs or lack of confidence in them.  It is really a function of risk.  For example debris strikes to the windows are more likely in first stage while still in the lower atmosphere.

Crew preference is to have the visors up as much as possible unless a cabin leak is detected.  Detection of a Cabin Leak becomes much easier in second stage when the differential pressure between the cabin and the ambient environment is greater.

Post SRB SEP, after second stage guidance is checked and the OMS assist is verified just hppens to be a good time to raise the visors and turn off the O2 flow.

The philosophy is pretty much the same for entry and landing.  Visors are checked down prior to rolling out on final (~10,000 feet).  Again that is when the threat to the windscreens is higher (i.e. bird strike).

Mark Kirkman
Mark Kirkman

Offline carmelo

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Re: What's up with the pressure suit visor rules?
« Reply #17 on: 02/19/2007 05:58 PM »
Think at Apollo astronauts and bubble helmet!

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