SpaceX Falcon Heavy with Air Force’s Space Test Program 2 (STP-2) payload will be launched in early 2017. One of the major payload seems to keep the schedule – it is Ball Aerospace research spacecraft BCP-100 with new propulsion onboard.
STP-2 mission was originally scheduled for October 2016 but due the delay with Falcon Heavy caused by changes implemented in rocket construction, it was postponed to early 2017. It appears that in contrast to delays in SpaceX, Ball Aerospace keeps the schedule accurately. In 31 March 2016, NASA confirmed that their spacecraft designed for Green Propellant Infusion Mission (GPIM) has just passed environmental and flight tests.
Mission is important step in changing face of the space industry to more environmental friendly. NASA keeps in mind how dangerous is most popular fuel for satellites, hydrazine. It is extremely flammable and explosive propellant which, in spite of very unstable character, is also extremely toxic. Even tiny amount of this substance is deadly so filling tanks of satellites requires great caution and could be performed only in special facilities. It is also very dangerous in case of failed launch of the satellite, when spacecraft could fall into ground and contaminate large area. Toxic nature of hydrazine is also one of the factors causing problems with the prevalence of Cubesat satellites with propulsion. Most of Companies which are manufacturing or assembling Cubesats could not afford to install expensive devices and build special facilities for storing and tanking hydrazine. It is worth pointing that even in case of big companies, handling with hydrazine is just additional cost. That is why NASA is started program of public-private partnership for developing technologies of green fuel and green propulsion for space industry.
Generally speaking GPIM bases on two parts: fuel and propulsion. Fuel used in this mission is hydroxyl ammonium nitrate based fuel/oxidizer propellant blend, known as AF-M315E. It was developed for military purposes and is less toxic than hydrazine. It was also designed to be less complicated in transportation, refueling and storing; in spite of these features it offers approximately 12% increased specific impulse and due the greater density (1.47 vs. 1.00 g/cc comparing to hydrazine) it could be stored in tanks of the same capacity. Usage of AF-M315E with new thruster system could give mass reduction for spacecraft at 30%, what will naturally affect on increased payload. Second part of GPIM is propulsion – new technology thruster designed by Aerojet Rocketdyne. On BCP-100 there will be 5 thrusters installed. Central with thrust at 22 N and specific impulse at 250 s (GR-22) and four vernier with thrust at 1 N and specific impulse at 235 s (GR-1). They were created especially to meet demands of new propellant. Their construction is resistant for acidic pH of new fuel; new type of valves was designed for higher net reliability and due the low viscous whole fuel system was designed with particular care for reducing potential leaks. Thrusters have also implemented series of technical solutions to be strong enough to manage perform as many starts as possible during 2 months mission. Aerojet Rocketdyne equipped thrusters in their patented LCH-240 catalyst to provide 15 times longer thruster life.
On picture above: visualisation of BCP-100.