QinetiQ supplied the onboard computer that guided the European Space Agency’s IXV spaceplane safely back to Earth after its maiden test flight on February 11. The IXV (Intermediate eXperimental Vehicle) represents ESA’s goal to develop a reusable autonomous vehicle for future space transportation. IXV lifted off from Europe’s Spaceport in Kourou, French Guiana, atop a Vega rocket. It separated from Vega at an altitude of 340 km and continued up to 412 km.
The flight control system provided the spacecraft with the intelligence necessary for a safe return flight, calculating the optimum angle for re-entering the atmosphere and making a controlled landing possible. QinetiQ was commissioned for the ESA project by the IXV's prime contractor, Thales Alenia Space.
“We were selected thanks to our strong track record in the development of similar systems,” said Koen Puimège, Business Development Manager for QinetiQ’s space business. “Guiding a spacecraft through its critical re-entry phase is never a simple task. As it hits the atmosphere at 27,000 km/h, experiencing temperatures of up to 1800°C, the craft must maintain the perfect angle and trajectory or risk breaking into pieces. The parachute and flotation devices must deploy at the right times and valuable data must be collected, communicated, and stored.”
As it descended, the 5-m long, 2-t spacecraft maneuvered to decelerate from hypersonic to supersonic speed. A very high level of reliability was required to ensure the computer operated effectively throughout the mission.
“The mission’s short duration meant there would be no time to reconfigure mid-flight during critical phases, so we developed a computer with a reliability rate of 99.997%,” said Puimège. “It was also essential that the backup systems react quickly, so we ensured a reboot could take place in nine seconds, compared to the 60 seconds typical for the reboot of a satellite control system.”
Because the re-entry of the IXV through the atmosphere did not allow for the use of solar panels to generate power, all power for the 100-min flight had to be provided by a single pre-charged battery.
“To avoid draining the battery, the computer, which is always on throughout the entire mission, must work as efficiently as possible,” said Puimège. “We designed IXV’s [computer] to operate on just 7 W of power. To put this into context, a home computer typically consumes between 65 and 250 W and a standard computer for a big satellite around 30 W.”
Despite its low energy requirements, low mass, and small size, the IXV computer needed to produce enough calculating power to simultaneously coordinate many crucial tasks.
“A typical spacecraft computer processes 10 million instructions per second (10 MIPS), while the IXV computer ran at five times that, delivering 50 MIPS,” said Puimège. “The computer responsible for the early Apollo missions generated around 2 MIPS.”
For the Vega rocket to overcome the Earth’s gravitational pull and set IXV on its suborbital path, the mass of everything on that entailed the craft had to be kept to a minimum. “The IXV computer is based on technology we developed for ESA’s tiny Proba-2 satellite, meaning it weighs in at less than 7 kg,” said Puimège. “In addition, the IXV vehicle was designed, for cost efficiency reasons, to be approximately 10 times smaller than the U.S. Space Shuttle, so everything had to be scaled down to meet that objective.”
IXV could be a suitable alternative to expensive space missions in the future, transporting cargo as well as astronauts into space and back again. Possible future uses include increasing the lifespan of existing satellites, Earth monitoring, testing new technologies, and performing fundamental research in space.
Upon re-entry, the IXV recorded a vast amount of data from more than 300 advanced and conventional sensors. The initial results from the flight are expected to be released sometime in April. It is expected the results will feature large in the Program for Reusable In-Orbit Demonstrator for Europe (PRIDE), which is being studied under funding approved at the Ministerial Conference in December 2014. The reusable PRIDE spaceplane would be launched on Vega, orbit, and land automatically on a runway. Early studies point to it having a winged body, making it guidable through various atmospheric environments.