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Homework Help: Need help finding the thrust and exit diameter of a rocket

  1. Oct 11, 2012 #1
    A small rocket powered by high-pressure nitrogen (R = 1776 ft-lb/slug/R, gamma=1.4) is used as an attitude control device. In space, the thrust of a rocket is given by T =mVe
    in lbf. Find the thrust and exit diameter of this rocket with a throat diameter of 1.0 inch if it
    operates at PT = 120 psi and TT = 510R with M = 3.0 at the exit. Then compare the
    thrust and exit diameters when the exit Mach number is 5.0 and 7.0.

    *I know I need to use the equation A/A*=(1/M^2)((2/gamma+1)(1+(gamma-1/2)M^2))^(gamma+1/gamma-1) but i'm having trouble finding the appropriate values.

    ps sorry if this post is in the wrong area, i'm pretty new to this site!!
  2. jcsd
  3. Oct 12, 2012 #2
    You've got everything you need, except for this part. The thrust equation is:

    F = m dot * Ve + (pe - p0) * Ae

    Calculate the exit area from the equation you listed. You've been given everything else. Or just look up the old tables.
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