a few questions...

Discussion in 'Space & Aeronautics' started by uglyguy9, Mar 24, 2008.

  1. uglyguy9

    uglyguy9 Member

    hi everyone,
    i have a few questions that i have posted on the nasa website.....but people here seem to know as much so i thought i would ask here as well.

    1. about 5 seconds before launch, there seems to be "sparks" coming from the base of the rocket (shuttle booster).
    is this to ignite the rockets?
    2. what is the difference is size between the friendship re-entry capsule and the apollo capsule?
    3. are the "strap-on" retro rockets from the friendship capsule "ejected before re-entry or do the just burn off in the atmosphere?

    try google but with mixed results ("ah the googles, they do nothing")
  2. Dyna-Soar

    Dyna-Soar Member

    1. The shuttle ignites its main engines ~6 seconds before launch, that way ground controllers can perform a mini-test of the shuttles engines or abort if needed, which is known as an RSLS YouTube - Space Shuttle Columbia Launch is Aborted at T-0:07

    2. The Mercury Capsule had a six foot diameter and was 9 feet long. The Apollo Capsule was 12 feet wideand was 11 feet tall.

    3. The Mercury Retropacks were designed to be jettisoned before reentry. However, on Friendship 7, a warning light came on indicating that the landing bag had deployed. Worried that this could mean losing the heatshield, Mercury Control deciding to have Glenn leave the retropack on during reentry. The landing bag light was a false alarm.
  3. uglyguy9

    uglyguy9 Member

    thanks Dyna-Soar
    that youtube vid was good....explained all
    thanks again :thumb:
  4. umtutsut

    umtutsut Member

  5. dhanners

    dhanners Member

    The "sparks" come from the SSME Hydrogen Burnoff System, and they do perform a function. During the SSME start-up sequence (but prior to ignition) hydrogen vapors are exhausted into the SSME nozzles. The concern is that a cloud of hydrogen could build up on the pad and explode below the Orbiter when the SSMEs ignite, and that could damage the engine bells. Also, combustion could be rough if there's a gas cloud there. So the HBS, which consists of six "hydrogen burnoff pre-ignitors," burns off the excess gas by spitting out all those neat little hot and luminescent balls.

    The SSMEs themselves are ignited by spark plugs, but they're not really the kind you find in your car. They fire for about 3 seconds to ignite the fuel and oxydizer, and once that gets going, the combustion is pretty much self-sustaining.
  6. A lot of people are un aware of the "Landing bag" on the Mercury capsule". It's an airbag cushion that deploys pushing the heat shield away from the capsule forming a large cushion for splashdown. In the Dyna-Soars previous explanation of Friendship 7's false light, keeping the retro pack on would hold the airbag back from fully inflating thus keeping the heat shield in place. Shepard was not told of the reason for keeping it attached until he landed. Though he did question it when told not to jetison it as they had not tested it in this configuration and no doubt he wondered if the airbag would properly deploy if the retro pac didn't burn up properly in the atmosphere. I have a picture somewhere of the Mercury capsule being lifted out of the water and you can see the heat shield hanging about 4' from the capsule. I never knew about the airbag until I inquired about that strange thing hanging from the capsule.
  7. Oops, errr madcow........... what can I say?
  8. Dyna-Soar

    Dyna-Soar Member

    Mea Culpa, It was late at night when I typed that.
  9. uglyguy9

    uglyguy9 Member

    as usual you guys are a wealth of information......and faster than nasa!
    thanks again
  10. Dyna-Soar

    Dyna-Soar Member

    I got that for Christmas last year along w/ From the Earth to the Moon.

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