[填空题]
The orbital velocity, v, 7i 9wqr,nle3 :jg 2n:esa q,o+kgddv4ofv9z jzo)q xv,u;g6 cdp )*obwysx8.+ g a spacecraft in km/s is given by
$v=−0.0098t+clnR$,where t is the firing time in seconds, c is the exhaust velocity in km/s and R is the mass ratio.
If R=30, find
1.The orbital velocity, v, after a firing time of 150 seconds and an exhaust velocity of 3 km/s. v ≈ km/s
2.The exhaust velocity, c, of the spacecraft traveling at an orbital velocity of 9.5 km/s after a firing time of 150 seconds. c ≈ km/s