2 A rocket for use in deep space is to be capable of boosting a total
3 load (payload plus rocket frame and engine) of $M_f = 3.00\U{metric
4 tons}$ to a speed of $v_f = 10.0\U{km/s}$.
5 \Part{a} It has an engine and fuel designed to produce an exhaust
6 speed of $v_{ea} = 2.000\U{km/s}$. How much fule plus oxidizer is
8 \Part{b} If a different fuel and engine design could give an exhaust
9 speed of $v_{eb} = 5.000\U{km/s}$, what amount of fuel and oxidizer
10 would be required for the same task?
15 Starting with equation 8.43 from page 248, and letting $M_e = M_i -
16 M_f$ be the mass of the fuel and oxidizer
18 v_f - v_i &= v_e \ln \left(\frac{M_i}{M_f}\right) \\
19 M_i &= M_f \exp^{\frac{v_f - v_i}{v_e}} \\
20 M_e &= M_f \left(\exp^{\frac{v_f - v_i}{v_e}} - 1 \right) \label{43.M_e} \\
21 &= 3.00\U{metric tons} \left(\exp^{\frac{10}{2}} - 1\right)
22 = \ans{ 442\U{metric tons}}
26 Using eqn. \ref{43.M_e} with our new exhaust velocity,
28 M_e &= 3.00\U{metric tons} \left(\exp^{\frac{10}{5}} - 1\right)
29 = \ans{ 19.2\U{metric tons}}