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Thread: My opinion (only my opinion, now) is that the 5-segments SRB can't work >>>

  1. #301
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    Ah ... I see ... so you don't know what the inserted mass was.

  2. #302
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    Quote Originally Posted by Bob B. View Post
    Ah ... I see ... so you don't know what the inserted mass was.
    in the sources I have there is not the data you want, but (if you remember) we are talking of the max weight the Shuttles' engines/motors can lift (for a comparison with the Ares-I) and that mass is 122.5 mT in real flights and 126.5 mT theoric (before the Challenger's accident mass' cut)

  3. #303
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    Quote Originally Posted by gaetanomarano View Post
    in the sources I have there is not the data you want, but (if you remember) we are talking of the max weight the Shuttles' engines/motors can lift (for a comparison with the Ares-I) and that mass is 122.5 mT in real flights and 126.5 mT theoric (before the Challenger's accident mass' cut)
    The problem of what a rocket "can lift" is not as easy as you want it to be. The engines are not only lifting the payload, but also the propellant, the tanks, and their own dead weight. And the mass it constantly changing as propellant is burned and components are jettisoned. You therefore have to define what "can lift" means. One way to define performance is by how much payload the launch system can deliver, such as to LEO, GTO, the Moon, etc. How much the payload weighs on the ground is not a meaningful way to define performance. In the case of the Space Shuttle, not all the mass at liftoff is useful payload. The Shuttle's OMS engines are often burned during ascent, and the OMS propellant is included in the orbiter's liftoff mass. That propellant cannot be considered payload because it is consumed during launch.

  4. #304
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    Quote Originally Posted by Bob B. View Post
    ...engines are not only lifting the payload, but also the propellant, the tanks, and their own dead weight...
    never had doubt of that
    ...how much payload the launch system can deliver, such as to LEO, GTO, the Moon, etc....
    for (both) Shuttle and Ares-I we talk of LEO, of course
    ...Shuttle's OMS engines are often burned during ascent, and the OMS propellant is included in the orbiter's liftoff mass...
    I know that, but, also without a few kg. of OMS propellant burned, the max Orbiter+payload mass sent to LEO still is up to 122 mT (or 126 mT theoric) not 109 mT

  5. #305
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    Quote Originally Posted by gaetanomarano View Post
    I know that, but, also without a few kg. of OMS propellant burned, the max Orbiter+payload mass sent to LEO still is up to 122 mT (or 126 mT theoric) not 109 mT
    109 mT is the maximum permissible landing weight on abort. I don't know what the maximum mass ever inserted into orbit is, though I've heard around 115 mT. Of course that mass includes the engines, piping, etc. that is really part of the launch system. When deducting the launch system components of the orbiter, I think we are left with around 100 mT.

  6. #306
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    Quote Originally Posted by Bob B. View Post
    I think we are left with around 100 mT.
    real flights contradicts your thinking
    piping doesn't weigh tons (and I don't believe it's included with the Orbiter weight since it is on the ET)
    probably, the Shuttle can launch up to 122 mT taking some risks in case of a flight-abort

  7. #307
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    Quote Originally Posted by gaetanomarano View Post
    real flights contradicts your thinking
    piping doesn't weigh tons (and I don't believe it's included with the Orbiter weight since it is on the ET)
    I'm talking about the piping that is internal to the orbiter. I don't know what it weighs but it was weighs something. The three SSME alone have a mass of 9.5 mT. You also have to deduct the propellant for the orbit circularization burn, which is about 1 or 2 mT.

    EDIT: We also have to deduct the weight of the thrust structure, which is probably several mT.

    Quote Originally Posted by gaetanomarano View Post
    probably, the Shuttle can launch up to 122 mT taking some risks in case of a flight-abort
    I doubt it. It stands to reason that the heavier the launch mass the more the OMS is burned during launch to augment the main engines. The OMS burn about 1 mT of propellant per minute. If they burn from SRB separation to MECO, that's about 6.5 minutes.

    I vote we end this discussion. We are merely splitting hairs and it is not really applicable to the point of the thread, which is the 5-segment SRB. Whether the Space Shuttle can deliver 110, 115, 120 or whatever mT to orbit is largely irrelevant.

  8. #308
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    Quote Originally Posted by Bob B. View Post
    I vote we end this discussion. We are merely splitting hairs and it is not really applicable to the point of the thread, which is the 5-segment SRB. Whether the Space Shuttle can deliver 110, 115, 120 or whatever mT to orbit is largely irrelevant.
    you've read, this discussion (like the similar discussion on an old thread) is shifted to how much payload can lift a rocket with the same tank/engines configuration of the Shuttle
    however, I give your same vote to end this discussion

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