Author Topic: Shuttle Q&A Part 5  (Read 521574 times)

Online anik

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Re: Shuttle Q&A Part 5
« Reply #675 on: 09/27/2009 10:40 AM »
what made Raffaello get chosen for PLM?

It appears that PLM will be Leonardo, not Raffaello.

http://www.collectspace.com/ubb/Forum30/HTML/000371.html (September 4, 2009)

"According to ISS Program Manager Mike Suffredini just two days ago, the MPLM to be adapted as the PLM is Leonardo (currently on-orbit with STS-128), not Raffaello. Suffredini did say the plan could change, but currently, Leonardo is it."

Offline psloss

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Re: Shuttle Q&A Part 5
« Reply #676 on: 09/27/2009 12:37 PM »
what made Raffaello get chosen for PLM?

It appears that PLM will be Leonardo, not Raffaello.

http://www.collectspace.com/ubb/Forum30/HTML/000371.html (September 4, 2009)

"According to ISS Program Manager Mike Suffredini just two days ago, the MPLM to be adapted as the PLM is Leonardo (currently on-orbit with STS-128), not Raffaello. Suffredini did say the plan could change, but currently, Leonardo is it."
Interesting post.  It was Suffredini that publicly identified Raffaello (FM-2) as the flight module to become the PLM earlier this year. (Edit: corrected by anik).

« Last Edit: 09/27/2009 02:41 PM by psloss »

Offline arkaska

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Re: Shuttle Q&A Part 5
« Reply #677 on: 09/27/2009 12:53 PM »
1) Why was MPLM Donatello never flight certified
2) and what made Raffaello get chosen for PLM?

3) One more MPLM question. Why has Leonardo been flying so much recently rather than Raffaello?

Thanks :)

Your third question is answered by your second question. They need time to refit the MMOD panels on Raffaello and do whatever else needs to be done to convert the MPLM into the PLM.

The answer to the first question is: $$$. By forgoing flight certification for Donatello, they save money that can then be spent elsewhere. Donatello was only going to have one flight anyway (was going to be 128 I believe). 

Donatello was planned to be used to transport "active" payloads to and from orbit. A good example of this is the MELFI freezer, they have 3 freezers that originally was planned to rotated on orbit. Since the Colombia disaster changed that they didn't have the need for Donatellos extra capability to keep continuous power.

Online anik

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Re: Shuttle Q&A Part 5
« Reply #678 on: 09/27/2009 02:20 PM »
Interesting post. It was Suffredini that publicly identified Raffaello (FM-2) as the flight module to become the PLM earlier this year

I doubt it was Michael Suffredini. It was Daniel Hartman, manager of Integration and Operations in ISS Program.

http://www.collectspace.com/ubb/Forum30/HTML/000371.html

"Dan Hartman, NASA's manager for the integration and operations of the International Space Station, addressed this topic today (May 6) during a press conference: "The study is back on the table so we're looking at adding what we call a 'PLM', a permanent logistics module to the International Space Station. And I believe it is 'Unit 2' and I'm not quite sure what that one [MPLM] is specifically called"

Offline psloss

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Re: Shuttle Q&A Part 5
« Reply #679 on: 09/27/2009 02:39 PM »
Interesting post. It was Suffredini that publicly identified Raffaello (FM-2) as the flight module to become the PLM earlier this year

I doubt it was Michael Suffredini. It was Daniel Hartman, manager of Integration and Operations in ISS Program.

http://www.collectspace.com/ubb/Forum30/HTML/000371.html

"Dan Hartman, NASA's manager for the integration and operations of the International Space Station, addressed this topic today (May 6) during a press conference: "The study is back on the table so we're looking at adding what we call a 'PLM', a permanent logistics module to the International Space Station. And I believe it is 'Unit 2' and I'm not quite sure what that one [MPLM] is specifically called"
You're right -- my mistake.

Offline kneecaps

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Re: Shuttle Q&A Part 5
« Reply #680 on: 09/28/2009 08:00 PM »

I think part of the reason you might be getting confused is because the PASS TRAJ displays were recently modified (in OI-32, STS-120 I believe) the picture I posted reflects my understanding of what the current displays look like for nominal ascent. 


Thanks, that explains why i've never even seen those displays! The old PASS TRAJ was very RTLS orientated. I'll try and find some docs detailing the new displays.

Thanks.
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Offline Lawntonlookirs

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Re: Shuttle Q&A Part 5
« Reply #681 on: 10/01/2009 04:39 PM »
Probably a dumb question and has been answered before although I wasn't able to find it on a search.  With the SSME having LO2 and LH as fuel, when the engines are first started, is it with the Liquid or gaseous O2 and H.  I was just wondering how it is vaporized before the engines are started or is it liquid when it ignites and during the flight?
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Online Danny Dot

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Re: Shuttle Q&A Part 5
« Reply #682 on: 10/01/2009 07:06 PM »
Probably a dumb question and has been answered before although I wasn't able to find it on a search.  With the SSME having LO2 and LH as fuel, when the engines are first started, is it with the Liquid or gaseous O2 and H.  I was just wondering how it is vaporized before the engines are started or is it liquid when it ignites and during the flight?

Only liquid is fed to the engines.  The start sequency is complex and I never understood it completely.  For example in a running engine the hydrogen runs in tubes in the nozzle to cool it.  This vaporizes the hydrogen.  When I taught an MPS class, I crossed my fingers no one whould ask how the darn thing starts.  I would admit I didn't have a clue, but had the name and number of a booster flight control they could bug. 

I found saying "I don't know" was better than making up stuff.

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Offline kneecaps

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Re: Shuttle Q&A Part 5
« Reply #683 on: 10/01/2009 07:31 PM »

Only liquid is fed to the engines.  The start sequency is complex and I never understood it completely.  For example in a running engine the hydrogen runs in tubes in the nozzle to cool it.  This vaporizes the hydrogen.  When I taught an MPS class, I crossed my fingers no one whould ask how the darn thing starts.  I would admit I didn't have a clue, but had the name and number of a booster flight control they could bug. 

I found saying "I don't know" was better than making up stuff.

Danny Deger

I was considering giving my understanding of what happens, but thinking about it i'm not sure of some specific details. Specifically when the ASIs (Spark igniters) actually start sparking.

Apparently only liquid head pressures and the ASIs sparking is actually needed to start, but I'd love to hear an expert explain or illustrate this!
« Last Edit: 10/01/2009 07:31 PM by kneecaps »
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Offline Lawntonlookirs

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Re: Shuttle Q&A Part 5
« Reply #684 on: 10/01/2009 07:48 PM »
Probably a dumb question and has been answered before although I wasn't able to find it on a search.  With the SSME having LO2 and LH as fuel, when the engines are first started, is it with the Liquid or gaseous O2 and H.  I was just wondering how it is vaporized before the engines are started or is it liquid when it ignites and during the flight?

Only liquid is fed to the engines.  The start sequency is complex and I never understood it completely.  For example in a running engine the hydrogen runs in tubes in the nozzle to cool it.  This vaporizes the hydrogen.  When I taught an MPS class, I crossed my fingers no one whould ask how the darn thing starts.  I would admit I didn't have a clue, but had the name and number of a booster flight control they could bug. 

I found saying "I don't know" was better than making up stuff.

Danny Deger

Thanks DD, so I guess it wasn't a dumb question after all.  Maybe a post on L2 would get an answer.  I checked the SSME Bible and it gives a lot of the information, but will take some time to digest for me.  "Download 2"

http://forum.nasaspaceflight.com/index.php?topic=4413.0

 
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Offline kneecaps

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Re: Shuttle Q&A Part 5
« Reply #685 on: 10/01/2009 08:02 PM »

Thanks DD, so I guess it wasn't a dumb question after all.  Maybe a post on L2 would get an answer.  I checked the SSME Bible and it gives a lot of the information, but will take some time to digest for me.  "Download 2"

http://forum.nasaspaceflight.com/index.php?topic=4413.0

 

It doesn't answer the question in a succinct way (if at all).
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Online Danny Dot

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Re: Shuttle Q&A Part 5
« Reply #686 on: 10/01/2009 11:15 PM »
snip

Apparently only liquid head pressures and the ASIs sparking is actually needed to start, but I'd love to hear an expert explain or illustrate this!


God himself spins up the turbopumps and breaths fire into the combustion chamber.  That's my story and I am sticking to it.   ;D

If someone figures out how those pumps go from zero to 100,000 hp in a couple of seconds -- please tell us all.

I think a key must be to get a fire going to blow hot gas through the turbines that drives the main pumps.  I don't think there is any kind of starter that spins the pump up.

Danny Deger

Edit: Ask more shuttle question, please.  The status of Ares I is getting old.
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Offline kneecaps

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Re: Shuttle Q&A Part 5
« Reply #687 on: 10/02/2009 08:01 AM »

I think a key must be to get a fire going to blow hot gas through the turbines that drives the main pumps.  I don't think there is any kind of starter that spins the pump up.



One of the first things that happens is the Main Fuel Valve ramps fully open, this allows LH2 to get to the preburners. Both the Oxidizer preburner and Fuel preburner valves also ramp open (but not fully) in the same time period. I'm thinking that the requirement for head pressure to start simply forces LOX and LH2 into the preburners (and the ASIs (igniters).

Pressure has forced LOX and LH2 into the preburners. This burns which causes a small amount of hot gas, this spins the turbines which in turn causes more LOX and LH2 to reach the preburners (which causes the pumps to spin faster, pumping more to the preburners, and so on).

At some point the igniters will stop since combustion in the preburners will become self sustaining.



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Offline psloss

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Re: Shuttle Q&A Part 5
« Reply #688 on: 10/02/2009 11:59 AM »
This link has been posted here before...the material there is at least historically related:
http://www.enginehistory.org/ssme.htm

Online Danny Dot

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Re: Shuttle Q&A Part 5
« Reply #689 on: 10/02/2009 12:53 PM »

I think a key must be to get a fire going to blow hot gas through the turbines that drives the main pumps.  I don't think there is any kind of starter that spins the pump up.



One of the first things that happens is the Main Fuel Valve ramps fully open, this allows LH2 to get to the preburners. Both the Oxidizer preburner and Fuel preburner valves also ramp open (but not fully) in the same time period. I'm thinking that the requirement for head pressure to start simply forces LOX and LH2 into the preburners (and the ASIs (igniters).

Pressure has forced LOX and LH2 into the preburners. This burns which causes a small amount of hot gas, this spins the turbines which in turn causes more LOX and LH2 to reach the preburners (which causes the pumps to spin faster, pumping more to the preburners, and so on).

At some point the igniters will stop since combustion in the preburners will become self sustaining.


OK.  I just thought of a key in starting the turbo pumps, vs. starting a gas turbine engine.  The preburner is where the fire is on the SSMEs.  There is only one way out -- across the turbine.   In a gas turbine, there is an opening at both ends and the turbine and compressor must be spun up by some means so the fire doesn't just go out the compressor.

I wish I would have thought of this while I still teaching the Main Propulsion System classes.

Danny Deger
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