GPS glitch kept Exos Aerospace’s first launch from reaching planned altitude

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WASHINGTON — The first flight of Exos Aerospace’s suborbital launch vehicle was “very successful” despite a malfunction that kept the vehicle from reaching its planned peak altitude.

The company launched its first Suborbital Autonomous Rocket with GuidancE, or SARGE, reusable sounding rocket Aug. 25 from Spaceport America in New Mexico. At the time of the launch the company said the flight went well, but provided few technical details about the mission’s outcome.

In a mission report provided by the company a week and a half after the launch, Exos said that a GPS receiver on the rocket stopped providing data during the rocket’s ascent. That triggered an automatic shutdown of the rocket’s engine 38 seconds after liftoff, versus a planned duration of 62 to 65 seconds, said John Quinn, chief operating officer of Exos, Sept. 5.

As a result of the early engine shutdown, the rocket reached a peak altitude of 28 kilometers, rather than the planned 80 kilometers. Quinn said an extrapolation of the rocket’s performance during that powered phase indicated the rocket might have been able to reach nearly 90 kilometers had the engine fired for the full duration.

The cause of the GPS unit malfunction in the rocket is still being studied. The unit started providing data again later in the flight, and an inspection turned up no obvious damage to the unit, cabling or antennas. There were separate dropouts of telemetry from the rocket during the flight, according to the mission report.

The report also explains a brief deviation in the rocket’s flight immediately after liftoff. The launch stool that the rocket was sitting on was not bolted to the ground because of the use of scales to weigh the rocket as liquid oxygen was loaded into it. Upon ignition, the stool was pushed to the side and hit the launch rail running alongside the rocket. That induced a torque on the rocket that the vehicle was able to correct within a second.

Despite the technical glitches, the company was pleased with what it called a “very successful” test flight of SARGE. Quinn said that other changes to the vehicle should enable the rocket to reach 100 kilometers — the Karman Line often used as the demarcation of space — on future missions.

SARGE is designed to carry up to 50 kilograms of payload, but Exos did not disclose what payload, if any, flew on this launch. Quinn said the company is looking for payloads weighing up to 25 kilograms to join an unnamed NASA payload on its next launch.