2. (10 pts.) A vertically launched sounding rocket has a payload of 150 kg and an empty weight of 1500 kg (excluding the payload). The rocket employs twin liquid engines with a storable propellant which provides an Isp of 280 s. The payload contains sensitive instruments that cannot withstand acceleration levels in excess of 4 g's.

a) Assuming negligible drag and that the engines are not throttleable, determine the propellant load, engine burn time, and engine thrust level that will maximize the performance (V) of this vehicle. What is the V achieved under these conditions?

b) It is suggested that the rocket may have additional performance by shutting down one engine down at some appropriate point in the flight. Determine in this case the burning times, propellant consumption, thrust level,