[填空题]
The orbital velocity, z f6 + a+i8w05 94ghcnzqlvopbv, of wuc *-t nrci 8g rb*,*;gkc.xta 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