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#160
by
MKremer
on 30 Jun, 2006 23:47
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Speaking of the SRBs...
The booster separation motors in the attached image look to have some pretty large environmental seals/covers on them. Are they removed before launch, and if so, when?
If they're left on, how much mass does each have, and how are they discarded when separation occurs (ie- whereabouts do they travel when they pop off as the motors fire?)
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#161
by
Jamie Young
on 01 Jul, 2006 03:01
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Don't the bolts fire, booster comes off, then it fires the motors a second later? By then the orbiters out of the way?
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#162
by
Jim
on 01 Jul, 2006 13:38
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Jamie Young - 30/6/2006 10:48 PM
Don't the bolts fire, booster comes off, then it fires the motors a second later? By then the orbiters out of the way?
Same time
Those covers have hinges and swing way, like barn doors
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#163
by
Rocket Guy
on 01 Jul, 2006 15:46
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The bolts release 1/1000th second before they ignite.
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#164
by
Jonesy STS
on 01 Jul, 2006 19:24
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Ben - 1/7/2006 10:33 AM
The bolts release 1/1000th second before they ignite.
Isn't that the hold down bolts, not the bolts that cover the top end nose cone trusters?
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#165
by
Rocket Guy
on 01 Jul, 2006 19:31
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Oh I misread, thought you meant the holddowns. Sorry.
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#166
by
Launch Fan
on 01 Jul, 2006 23:04
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I saw that there was venting out of the top of the tank, Liquid Oxygen, but why was there venting out of the bottom of Discovery near her SSMEs? I thought only Liquid Oxygen had boil off, or am I totally wrong?
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#167
by
Jim
on 02 Jul, 2006 02:33
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Launch Fan - 1/7/2006 6:51 PM
I saw that there was venting out of the top of the tank, Liquid Oxygen, but why was there venting out of the bottom of Discovery near her SSMEs? I thought only Liquid Oxygen had boil off, or am I totally wrong?
they are purging and conditioning the engines to cool them down so that there is not cryogenic shock
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#168
by
Chris Bergin
on 02 Jul, 2006 17:13
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Welcome to the site - and thanks for the kind words, plus your battles against the "it looks like an alien washing machine on Mars" types.
As I like to say, "No, it's damn rock!"
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#169
by
Chris Bergin
on 03 Jul, 2006 08:27
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Thanks Robert -
I'll contact you by e-mail or PM.
Robert A.M. Stephens - 3/7/2006 2:10 AM
(Trivia: What was the first words John Young said on air, publicly, to the world after he raced down off the orbiter, right after landing and safing of the bird to a point him and Crippen could egress, at the end of STS-1?)
Robert
Damn, this has got me, as I can only recall the "Would you like me to park her in the Hanger" "I think we'll dust her down first" comments, on rollout down the runway." plus the "She's the world's greatest electric flying machine".
I bet Ben E knows
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#170
by
astrobrian
on 03 Jul, 2006 12:20
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I was looking at some of the older mission patches and realized they don't put the orbiters name on them hardly at all anymore. why not?
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#171
by
Jim
on 03 Jul, 2006 13:21
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astrobrian - 3/7/2006 8:07 AM
I was looking at some of the older mission patches and realized they don't put the orbiters name on them hardly at all anymore. why not?
There weren't that many orbiters at the time, now a mission might switch orbiters
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#172
by
EVA
on 03 Jul, 2006 14:15
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Chris Bergin - 3/7/2006 3:14 AM
Thanks Robert -
I'll contact you by e-mail or PM.
Robert A.M. Stephens - 3/7/2006 2:10 AM
(Trivia: What was the first words John Young said on air, publicly, to the world after he raced down off the orbiter, right after landing and safing of the bird to a point him and Crippen could egress, at the end of STS-1?)
Robert
Damn, this has got me, as I can only recall the "Would you like me to park her in the Hanger" "I think we'll dust her down first" comments, on rollout down the runway." plus the "She's the world's greatest electric flying machine".
I bet Ben E knows
When I first read the question, the traditional aviation phrase said after the first flight of an airplane, first said after the the first flight of the B-17, "We've got a winner!", came to mind, but after reading Chris' reply, I think he's on the right track, wasn't it something like "Dust her off and put her in the hangar."?......I dunno.
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#173
by
Duff
on 03 Jul, 2006 16:50
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Hello everyone
I would first of all like to thank the moderators and the people who post here for such a great site.
Ok,
The Crawler Transporter ( CT ), carrying the Mobile Launch Platform (MLP) and the shuttle stack has just made its long walk from the Vehicle Assembly Building (VAB) to the launch pad.
Once there:
1) how long does it take to get the MLP in the right spot?
2) is there a area marked where it must go, or is it lined up using lasers?
3) how accurate must it be or is there a allowance for it be so far out of square or in line?
4) if the MLP is out of square, can the CT spin with the tracks in opposite directions to square it self up or does it have to walk back a bit and line up better?
5) are the hard stands there already in place or they put under MLP with a forklift?
6) is the MLP bolted and torqued to the hard stands ( and the hard stands to the pad ) or is it just free standing and will not move due to the weight of the whole structure?
7) how long does it take to have the MLP ready for launch ( on the hard stands, hydrogen and oxygen lines connected, noise suppression water lines connected, electrical harnesses connected and everything else that I have not included)?
Much appreciated for any answers
Duff
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#174
by
selden
on 03 Jul, 2006 17:01
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wasn't it something like "Dust her off and put her in the hangar."?
According to SpaceMad on this Forum's own Quotes page, it was
"Do you want me to park her in the hanger?" - "I think we'll dust her down first!" Young and Houston talking after landing Columbia on STS-1
note: this is in response to EVA, not the trivia question.
This doesn't sound like something you'd say after you've left the orbiter.
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#175
by
Jim
on 03 Jul, 2006 19:56
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Duff - 3/7/2006 12:37 PM
Hello everyone
I would first of all like to thank the moderators and the people who post here for such a great site.
Ok,
The Crawler Transporter ( CT ), carrying the Mobile Launch Platform (MLP) and the shuttle stack has just made its long walk from the Vehicle Assembly Building (VAB) to the launch pad.
Once there:
1) how long does it take to get the MLP in the right spot?
2) is there a area marked where it must go, or is it lined up using lasers?
3) how accurate must it be or is there a allowance for it be so far out of square or in line?
4) if the MLP is out of square, can the CT spin with the tracks in opposite directions to square it self up or does it have to walk back a bit and line up better?
5) are the hard stands there already in place or they put under MLP with a forklift?
6) is the MLP bolted and torqued to the hard stands ( and the hard stands to the pad ) or is it just free standing and will not move due to the weight of the whole structure?
7) how long does it take to have the MLP ready for launch ( on the hard stands, hydrogen and oxygen lines connected, noise suppression water lines connected, electrical harnesses connected and everything else that I have not included)?
Much appreciated for any answers
Duff
they use lasers and sights.
there are supports already in place.
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#176
by
Jim
on 04 Jul, 2006 16:18
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Nick L. - 4/7/2006 10:54 AM
What is the purpose of the AstroVan vehicle? Is there some sort of contamination hazard that the AstroVan helps to avoid?
Nick
Just a mode of transportation that has the size for 7 crew members and other support personel and extra cooling for the crew and cooloinghook ups for their suits
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#177
by
zinfab
on 06 Jul, 2006 00:41
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I never asked this question, but the answer was so good, I had to copy it here.
http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=3149&posts=10&start=1nuchem - 5/7/2006 12:13 AM
1. When propellant is pumped out of the tanks the tank pressure will drop. Low pressure could cause cavitations of the propellant and implosion of the tank. How does one avoid this pressure drop? Has it never posed a problem? I can think of numerous ways to solve it I wonder what’s been done in practice.
buckwheat wrote:
The shuttle's ET is pressurized by an "autogenous" pressurization system. This means that the tanks are pressurized by some of the propellant they are carrying, during flight. Here's how this works. As the engines pull in propellant during flight, a small bit is tapped off and run through a heat exchanger. This converts the LOX or LH2 into gas. This gas is then sent up, via the GO2 and GH2 presslines, to its respective tank. The gas enters the upper part of the tank ullage (ullage = gas space in a propellant tank, as opposed to the liquid space) through a diffuser, which evenly spreads the pressurant gas throughout the upper part of each tank.
The flow of these pressurant gases on the Space Shuttle is slightly different between the LH2 and LOX tanks. Initially, both systems used "Active Flow Control Valves" (located just downstream of the SSMEs, inside the Orbiter) which controlled the flow of pressurant gases exiting the SSME heat exchangers. The valves would remain open when the tank pressure went below a certain set point (in the case of LH2, the set point is 32.5 psia) and open when the pressure went above a certain set point (for LH2, this is 33.5 psia). FCV from SSME #1 is tied directly to the pressure of LH2 tank pressure transducer #1, FCV #2 to XDCR #2, and so forth with #3. Incidentally, when the valve is "closed" a low flow of GH2 flows through it, and when it is "open" a high flow passes through it.
Starting with STS-40, the LOX tank has been pressurized with a "Fixed Orifice Pressurization System". Basically, there were so many failure modes associated with these Flow Control Valves (such as valves sticking open - whether due to valve failure or transducer drop-out during flight) that it was decided to try a system that used a fixed flow orifice, and no valves, and after careful analysis and testing (the four flights between STS-35 and STS-39 used "shimmed" valves that zeroed in on the 78% size eventually chosen) the correct size was found, and that is still in use today. This gives the LOX tank pressure profile a very noticeable flight profile, complete with a "slump" initially and an "overshoot" later in flight. The LOX tank pressure transducers read pressure in "psid", which differs from PSIG slightly (since the ducers are located in the ET nosecap compartment, the "d" is the differential pressure between the NC compartment and ambient). The range is from about 13 psid during the "slump" about 10-15 seconds into flight, to about 25 psid around T+250 seconds. The ICD limits on LOX tank ullage pressure are pretty generous, allowing this range - the only bottleneck apparently occurs during Max-Q (65-80 sec or so) when stress requirements on the tank narrow the range considerably.
This system has worked just about flawlessly for the Shuttle ET since STS-1.
Incidentally, because of stress and NPSP requirements with the LH2 tank, a similar Fixed Orifice system could not be implemented there... however, a few years ago (STS-97?) a "shimmed" orifice system was implemented for the LH2 tank, which significantly reduced the number of FCV cycles during flight. This also greatly lessened the risk of a tank overpressurization during flight (GH2 venting during flight is considered, since STS-51L, a CRIT-1 failure) and also helped on the low side, reducing the chances that the "Astronaut Logic" specified in the Shuttle Flight Rules would need to be used (and protecting against NPSP dropout - i.e., cavitation).
Hope this helps. Probably more than you wanted to know, I used to work with one of these systems and still remember it well.
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#178
by
darkenfast
on 06 Jul, 2006 02:59
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Re: the John Young trivia question (just a guess): "I need to pee!"
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#179
by
astrobrian
on 06 Jul, 2006 03:05
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the dust her off line wasnt said once he stepped out, that was said just before wheel stop.
