The Mk V is a fifth generation Nitrous Oxide/HTPB hybrid rocket engine which is throttleable from 100% to 50%, can burn for more than 60 seconds, and produces 3,000 lbf (13.3 kN) of thrust at sea level. The engine was designed to fly on Starscraper. The Mk 5 configuration for Starscraper had the capability to be throttled back during flight in order to limit vehicle acceleration and extend the burn time so that engine shut off would have occured outside the atmosphere, allowing for full control.
Like the Mk IV motor, the pressurization system on the Mk V allowed the rocket to be run at a higher pressure, resulting in improved specific impulse. This increased pressure difference across the injectors allowed for more stable combustion and the higher pressure results in lower thrust trail off which means the engine can stay at optimal efficiency for a greater period of time.
Rather than relying on fins to stabilize the rocket, the Mk V employed the use of a technique known as liquid injection thrust vector control (LITVC).This technique involves injecting liquid N2O into ports around the nozzle, creating supersonic shockwaves which have the effect of shifting the direction of thrust. Thrust vector control would have been used to keep the rocket stable during its ascent through the atmosphere.
Before re-entry, the roll control thrusters fire and cause the rocket to tumble during atmospheric interface. This would have allowed for increased energy dissipation as the vehicle re-entered Earth’s atmosphere, eliminating the need for a heat shield.
The thrust vector control and long duration burn technologies implemented on the Mk V have been developed and tested on the Mk IIB motor, while the flight control algorithms and electronics have been tested using ASTRo.
starscraper/Mk 5 Technical Overview
Height: 30 ft (9.1 m)
Launch Mass: 1,100 lb (498.95 kg)
Diameter: 12 in (0.3 m)
Engine: Mk V
Burn Time: 60 sec
Payload Capacity: 100 lb (45.35 kg)
Thrust at Sea Level: 3,000 lbf (13.345 kN)
Thrust in Vacuum: 3,300 lbf (14.679 kN)