From: BrianT@cup.portal.com (Brian Stuart Thorn)
Newsgroups: sci.space.shuttle
Subject: Re: Re : Shuttle as an space tug...
Date: Fri, 22 Jan 93 17:31:09 PST
Organization: The Portal System (TM)

>Two different spacecraft.  Two different objectives.  The Saturn-V had almost
>all fuel as weight.  Shuttle is a payload delivery system to low earth orbit.
>The Saturn-V was dropping off pieces / parts of the system all of the way to
>the moon and back until all it was moving was a small capsule to return men to
>the ocean.  A capsule, I might add, that could VERY easily fit in the shuttle
>bay with room for a real payload...

    At Trans-Lunar Injection (TLI), there was still a very large mass to
    move around, on the power of a single J-2 engine. Could not a
    Shuttle haul itself to the moon and back on the power of 3 SSMEs?
    Apollo CSM and LM weighed, what? 80,000lbs or more, right? Now add
    in the S-IVB...
    
    What came back from the moon is irrelevant, as that mass (Apollo CSM)
    had to be moved on the power of the SPS (Service Propulsion System,
    the big engine in the Apollo Service Module.) The Shuttle would
    still have its three Main Engines and External Tank.

>Where DO you get your info from... APU's are in the aft compartment, along wit
h
>all of the electronics for the APUs, electronics for the SSMEs, electronics fo
r
>the aft OMS / RCS pods, the SSMEs, water spray boilers, APU fuel tanks, misc.
>hydraulic lines, misc. freon cooling lines, lots of wiring.

    Yep, I blew it on the APUs, and you aren't the only one to point
    that out. Still, I could've sworn the APUs are beneath the payload
    bay... (By the way, what are all those vents along the side of the
    orbiter below the bay doors for?)

>>wouldn't be required, either. If we seriously wanted to use old
>>Shuttles as OTV, strip the SSMEs off and pull out the APUs. They
>
>How would we strip out these items?  Once again, these are man intensive items
>to pull during ground servicing, much less in space.  You need the SSMEs to ge
t
>to orbit, so the only place to pull them is in space.  Same with the APU's.

    I was thinking along the lines that they would have PLENTY of time
    to do the work, not just a week on orbit. Base it at Freedom and
    do the work a little at a time.
    
    Regarding the SSMEs, I recall several times that they changed the
    engines on the launch pad. Clearly, the OPF is not mandatory for
    engine change-out, but equally clearly, it wouldn't be easy to do
    on orbit.

>>are already designing a Solar Powered Extended Duration Orbiter
>>(SPEDO) kit, so use that to replace the maintenance-intensive
>>fuel cells. What's left isn't that complicated. OMS and RCS are
>>already designed for multiple flights before heavy maintenance.
>
>How do we fuel these?  They would have to be redesigned for astronaut
>servicing.

    They refuel Mir periodically on orbit...
    And they were about a year away from refueling Landsat, a spacecraft
    not designed for refueling. Aside from the carrier of the fuel, what
    would have to be redesigned to refuel the OMS at Freedom?
    
>>Remember that Apollo was *much* lighter than the shuttle. Besides, in
>>Apollo, parts of the vehicle were jettisoned when they were not needed
>>any more. For example the S-IVB was jettisoned after TLI; something that
>>can't be done to an ET, if it contains the fuel for subsequent burns.
>>The SPS was only used to get on and off lunar orbit and course corrections,
>>both of which requires much less velocity change than TLI.

>>No disputing that, but the previous poster claimed that Trans
>>Lunar Injection (TLI) required x (3 times?) the energy of the
>>boost from Earth to LEO. I was simply saying that is not true,
>
>The original post did not specify from LEO, and I said it took 2 times the
>energy.  See the previous post as I was wrong.  From surface to the moon, it i
s
>about 11 times more energy.

      11 times more energy that WHAT? Did Saturn 5 have 11 times more
      energy than Shuttle. I think I'm hopelessly bogged down by
      numbers on this one. If you say so...

>>load for TEI. Then again, even a single SSME has an order of
>>magnitude more thrust than the Apollo SPS engine.
>
>The Apollo (Saturn V) J2 engine was 230,000 Lbs thrust, the SSME is 512,300 Lb
s
>thrust (Aerospace America, November 1991).  Not even close to an order of
>magnitude.

      Please refer to the previous paragraph. I was talking about TEI,
      or Trans Earth Injection, which was powered by the 20,500 lb.
      thrust SPS engine in the Apollo Service Module. Yes, we are indeed
      talking an order of magnitude.

      Even so: 1 J-2 engine - 230,000lbs thrust.
               3 SSMEs - 1.4 million lbs. thrust.

>You might wish to thoroughly read previous posts before wading in so daringly
>8-}.  As en explained previously, there are MANY black boxes throughout the
>shuttle, including 3 avionics bays in the aft with dozens of electronics boxes
>in each.  Changing these out is a pain even on the ground, and we change one
>out every other mission or so.  You would have to do this in orbit, and withou
t
>special redesign, I doubt that the astronauts could even get through the doors
>or into thru the aft thrust structure in a pressure suit to even GET to these
>boxes much less change them out.  You would also have to redesign the OMS pods
>for on orbit refueling.

      Rushing in where angels fear to tread point taken. I thought all
      OMS electronics and support was in the OMS pods and also thought
      that all electronics (black boxes) in the aft compartment were
      entirely related to the Main Engines.
      
      What *is* the stuff in that area for, anyway? We're building
      black boxes for satellites that last ten years, and Freedom is
      not going to have frequent electronics changeout, is it? Can
      we not replace the more limited lifespan electronics with
      equipment designed for Freedom?

>Once again, you might wish to review the previous posts.  SSMEs are not just
>fill em up & light em.  The Saturn - V J-2 was restarted only after the
>thrusters on the sides were run and some of the boiling off LO2 & LH2 was used
>for thrust.  This settled the LOX & LH2 in the tank.  The thrust chamber of th
e
>J-2 also recirculated LH2 before it was lit.  The SSME requires a few hours of
>chilldown with the LOX being dumped on the ground, and then during final count
>an hour of chilldown minimum.  The LH2 is also required to recirculate, but
>that goes back into the LH2 tank.  Translation, the SSMEs are not easy to get
>set up correctly for launch.

    Fill 'em and light 'em. Maybe you paragraph here goes along way
    toward explaining many trepidations about the DCX, DCY, etc.

    I mentioned the ullage problem in a previous post. If the RCS can't
    handle that duty, I stand corrected. Can it?
    
    The basis of my statements about SSME restart was a previous post
    in which it was said that the SSMEs would not require substantial
    modifications to be restarted in space. Go flame that person, if
    you don't mind... :-)
    
    Please note that in each post I stated that I was *not* advocating
    using the Shuttle to go to the Moon. I just don't like the quick
    "no" answers to that question. I'd like to know why not.

    Also, there was a post here a few weeks ago that a NASA official
    once said that the Shuttle could go anywhere in the solar system
    on a full ET.

    -Brian

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Brian S. Thorn                                    "If ignorance is bliss,
BrianT@cup.portal.com                               this must be heaven."
                                                -Diane Chambers, "Cheers"
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Newsgroups: sci.space.shuttle