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Thread: More reasons Solids might be better for Ares.

  1. #1
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    More reasons Solids might be better for Ares.

    here


    but a metal guide pin that jammed while engineers attempted to route a liquid hydrogen fuel line between the shuttle and its external fuel tank set the process back a few days
    .

    And

    engineers are also hunting for the source of an odd sound heard when another shuttle fuel tank, reserved for the Endeavour orbiter, was hoisted into a vertical position.
    Iím not sure I would want to fly next to that tank. But it does show some of the things that wonít cause delays on an Ares. I still think NASA is on the right track.



    As a side note from the same link:

    NASA plans to perch Endeavour atop a second shuttle launch pad and ready it to fly within 25 days of an emergency, if required, Atlantis astronauts have said.

    I didnít think a shuttle could last that long in orbit? What is there absolute maximum time in orbit, including safety margins?

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    Quote Originally Posted by samkent View Post
    I didnít think a shuttle could last that long in orbit? What is there absolute maximum time in orbit, including safety margins?
    I've never heard one way or another, but, my guess is that it has a lot to do with consumables which could be increased for this mission only.
    Plus; in an emergency situation, there can be conservation of resources, and maneuvering is probably not an issue (fuel usage).

    The only things that I can think of is if the fuel storage itself has a lifespan itself (built in loss or something like that), or if there are other capacity items that can't be re-filled, or backed up.

    In other words... I'd like to know too.

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    The Shuttles get their electrical power from fuel cells. These cells consume hydrogen and oxygen to produce electricity and water. In the event of an emergency, they can reduce their electrical consumption somewhat to extend the mission. However, I can't find out how long they could go if they had to. If I had to guess, I'd put the upper limit at perhaps 4 weeks.

    Part of the determination is based on when the problem occurred. If the problem occurred on the first day of the mission and they reduced electrical consumption immediately, they'd be in better shape than if it happened later in the mission when a great deal of the LH/LOX had already been consumed.

    How long can they store hydrogen before it boils off? I don't know. How low can they go with water production and still have enough to meet the crew needs? I don't know.

    The only things that I can think of is if the fuel storage itself has a lifespan itself (built in loss or something like that), or if there are other capacity items that can't be re-filled, or backed up

    The propellants used for OMS and attitude control are hypergolics. While nasty, toxic, and corrosive, hypergolic propellants can be stored for very long times. Satellites routinely use hypergolic propellants for their propulsion for many years after launch.
    Last edited by Larry Jacks; 2008-Aug-28 at 07:26 PM. Reason: Added discussion about fuel

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    Since they lost the last one, they are also trying to put all of the remaining Shuttle flights in orbits that can rendezvous with the ISS (or go directly to the ISS, not counting the Hubble servicing mission in October) so they can dock and ride out any problems there. At the ISS they also have the option of riding down in a Soyuz return capsule.

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    Quote Originally Posted by Larry Jacks View Post
    The Shuttles get their electrical power from fuel cells. These cells consume hydrogen and oxygen to produce electricity and water. In the event of an emergency, they can reduce their electrical consumption somewhat to extend the mission. However, I can't find out how long they could go if they had to. If I had to guess, I'd put the upper limit at perhaps 4 weeks.
    I believe I've read that not all fuel cells are required to run, but NASA is reluctant to shut any down, because of a non-trivial risk that it can't be started again. I don't know how that works with fuel cells, so don't take my word for it, but if it's correct maybe they could stretch the mission by shutting one or more off.

    I know that I've seen a comprehensive article on all the rescue implications but of course I neglected to bookmark it
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    Do they have onboard batteries? I assume they must have one or two for specific systems. Radios? Emergency lighting?

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    Maybe they could use a hand or foot crank dynamo.
    Et tu BAUT? Quantum mutatus ab illo.

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    The shuttle orbiter can be equipped with additional LH2-LO2 aux tanks via cargo-bay pallets for long duration missions to power the fuel cells and as breathing O2. The longest mission to date is STS-80 at seventeen days, with the next two longest at sixteen days.

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    Quote Originally Posted by samkent View Post
    Do they have onboard batteries? I assume they must have one or two for specific systems. Radios? Emergency lighting?
    No batteries

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    Quote Originally Posted by samkent View Post
    here

    Iím not sure I would want to fly next to that tank. But it does show some of the things that wonít cause delays on an Ares. I still think NASA is on the right track.

    Wrong again. Flawed logic.

    NASA is not making an all solid vehicle.
    The same things can happen on the Ares I upperstage. So your point is null.

    NASA is not using solids because they are safer, they are using Shuttle solids because of demonstrated flight record. NASA would not be using solids if it was a brand new design because it would not be safer.

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    Quote Originally Posted by The Jim View Post
    Wrong again. Flawed logic.

    NASA is not making an all solid vehicle.
    The same things can happen on the Ares I upperstage. So your point is null.

    NASA is not using solids because they are safer, they are using Shuttle solids because of demonstrated flight record. NASA would not be using solids if it was a brand new design because it would not be safer.
    Jim, you put it so well It is so obvious about the 'why' but so many want to argue every little point no matter the relevancy. If only those doing the arguing could/would go back to Day 1 of the decision to use a SRB for Ares, it (the 'why' that is) is spelled out clearly (!). Being so distant though makes it harder to see unfortunately, so the arguments will likely continue until the Sun consumes all its fuel, LOL...

    Alex

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    Everyone knows Ares I uses a solid first stage because of its coolness factor. I mean, the roar of that thing, seriously... :-)

    Without going too much into politics, would the fact that using an SRB makes the Ares first stage reusable have any positive political influence?

    Of course, if on the other hand they would be able to use an LOX/LH2 first stage with a clean plant, that'd be better on the exhaust part of the comparison, so...

  13. 2009-Oct-28, 08:52 PM
    Reason
    Wrong thread.

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    Quote Originally Posted by Nicolas View Post
    would the fact that using an SRB makes the Ares first stage reusable have any positive political influence?
    I doubt it. It's not like you just fill-er-up and go again.

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    Depends on how you communicate the procedure.

    I for one like the idea of some parts being resued. Not that it's the ultimate goal for me, but it's elegant.

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    Quote Originally Posted by Nicolas View Post
    I for one like the idea of some parts being resued.
    Are you a lawyer? Why else would you like to see parts sued? More than once?
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    You nearly got me there. I'm not a lawyer. I make wigs.

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    Quote Originally Posted by Nicolas View Post

    Without going too much into politics, would the fact that using an SRB makes the Ares first stage reusable have any positive political influence?
    Reusable is a misnomer. The booster is rebuilt for each flight. The avionic wiring, hydraulic plumbing, thermal protection, etc has to removed and replaced.

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    I like to think of it as "recoverable" rather than re-usable.
    First step, is to eliminate a booster from being clutter or a danger in orbit or on the ground or sea on returning.
    Once it's recovered, then the meter can be running on the benifits of reusability.

    If it's cheaper to re-build after recovery, then so-be-it. Otherwise, recycle it and build another.

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    Good point. Recoverable is a nice start, a very good EOL philosophy.

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    the shuttle is not what I'd call fully reusable either. it too need a major overhaul between flights.
    Once we start talking about number of flights between overhauls, Then we can claim the reusable title.

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    Or very short overhaul times at least. Something like SS1, which could be launched every week after minor works, is getting quite reusable. In comparison, a space shuttle is more like something that goes up as a space plane and comes back as a parts kit to build another one. (hyperbole). It is reusable, but it requires so much effort that it is more like "recycled for the same purpose as the original".

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    Doesn't looks like this SRB would be reusable ( although I doubt they had plans to anyway ) - it's been heavily dented at some point - possibly during impact with the water

    http://spaceflightnow.com/ares1x/091029dent/

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    although I doubt they had plans to anyway
    I bet they did. They always do. The 5 segment ground test earlier this year used an SRB stage which had already flown on STS-1.

    They'll have to investigate whether the chutes opened correctly, as the dent in itself doesn't prove anything either way. If you've ever handled sea containers, you'll know the kind of dents waves & water can make in steel structures.

    The chutes did open correctly in a plane drop test a few weeks ago. They'll have some research to do to determine the chute status for this flight however, as there is -AFAIK- no video footage of it.

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    Quote Originally Posted by Nicolas View Post
    I bet they did
    I bet they didn't - it was mentioned during the countdown that the pieces of this SRB were going 'spare' as they were past their useful life for the shuttle program.

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    Didn't know that. Thanks for the info.

    Good thing I always bet for nothing.

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    Quote Originally Posted by jamestox View Post
    The shuttle orbiter can be equipped with additional LH2-LO2 aux tanks via cargo-bay pallets for long duration missions to power the fuel cells and as breathing O2. The longest mission to date is STS-80 at seventeen days, with the next two longest at sixteen days.
    The shuttle in stock configuration has a nominal on-orbit duration of about 7 days. There's some contingency reserve beyond this.

    There was an Extended Duration Orbiter Pallet (EDO), which carried extra consumables to boost nominal on-orbit duration to 16 days. However the only EDO pallet was destroyed with Columbia. I think Atlantis had the plumbing for EDO, but was removed to lighten weight since all remaining missions are to ISS.

    Maximum on-orbit duration was investigated during the Columbia accident hearings, with a view to hypothetical rescue missions for a stranded shuttle.

    Since Columbia had the EDO pallet installed, the main limitation was not power, water or oxygen. Rather it was lithium hydroxide cannisters needed to remove CO2 from the cabin atmosphere. Models indicated Columbia's crew could have survived in orbit about 30 days before exhausting the LiOH cannisters. That's roughly a 2:1 stretch over the nominal 16 day ability, and involved power down, minimal crew activity, etc.

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    Quote Originally Posted by joema View Post
    The shuttle in stock configuration has a nominal on-orbit duration of about 7 days. There's some contingency reserve beyond this.
    10 days

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