Fourth launch of SARGE suborbital rocket fails

by Chris Gebhardt

After recovering from an unexpected navigation issue that triggered an in-flight engine shutdown on their last mission, Exos Aerospace was ready to return to flight with the fourth launch of their suborbital SARGE rocket. 

The quick, up-down mission was tasked with carrying experiments from nine universities and research organizations and will launch from Spaceport America in the U.S. state of New Mexico.  However, the vehicle failed after a wobbly ascent and failure to abort properly resulting in the vehicle impacting with the ground without its trademark parachute recovery.

SARGE stands for Suborbital Autonomous Rocket with GuidancE (SARGE) and is a Suborbital Reusable Launch Vehicle (SRLV) from Exos Aerospace.

Built on the STIG B platform, SARGE is a Liquid Oxygen/ethanol bipropellant vehicle using an LE23000FC series engine to produce 24.4 kilonewtons or 5,500 lbf of thrust at liftoff.

Standing 11 m (36 ft) tall and 51 cm (20 inches) in diameter, the sounding rocket (another name for small, suborbital vehicles) is capable of carrying a fleet of small scientific experiments weighing up to 50 kg total up to an altitude of ~80 km (49.7 miles).

Launching from Spaceport America, the Federal Aviation Administration – or FAA – in the United States issued Exos Aerospace a reusable launch vehicle mission launch license on 14 February 2018. 

A successful pathfinder mission proving the SARGE’s reusability and performance as a rocket was accomplished six months later on 25 August 2018.

The intended altitude was 80 km; however, an onboard GPS receiver issue resulted in an early shutdown of the engine and a maximum altitude of 28 km.

Despite the early engine shutdown, SARGE’s recovery equipment worked as expected, and the rocket was recovered from the New Mexico desert – after which it was refurbished and relaunched on 2 March 2019. 

That second mission also targeted 80 km, but high upper level winds resulted in a maximum altitude of just 20 km. 

The second mission was the first SARGE flight to carry science experiments and research payloads. 

Again, SARGE was recovered and refurbished for a third flight which took place just three months later on 29 June 2019.

The third flight was also to reach 80 km and also carried scientific research payloads aboard. 

However, nanoseconds after liftoff, the navigation and directional control system began to malfunction, wiggling the rocket instead of keeping it on a straight and true course. 

At first, this issue was corrected, but within seconds developed again. 

The repetition of the issue caused the onboard systems to shutdown the engine.  The rocket coasted up to 14,000 feet before deploying its parachutes and landing safely back on Earth. 

All payloads were recovered successfully.

Exos quickly traced the problem to an imbalance between the navigation and control systems and has used the data recovered from the intact SARGE landing from its third flight to help perfect and correct the balance.

The main corrective action saw the implementation of a new Inertial Measurement Unit (IMU) system.

As part of the Return To Flight plan, Exos conducted a tethered “rocket hover” test with SARGE and its new IMU on 1 October 2019.

The new guidance system performed as expected and demonstrated “positive stable control throughout the short duration test,” noted an Exos Aerospace release announcing SARGE’s fourth flight

This flight will once again had a goal of seeing SARGE reach an 80 km point above Earth’s surface before descending back down for landing and recovery. This was unsuccessful.

The launch appeared to be going well for the opening seconds before the vehicle started to roll. Once the view was restored, the vehicle was seen to be returning in multiple parts with the main section failing to return under chute resulting in it impacting the ground.

As with the previous two flights, the mission carried scientific payloads and research experiments from nine universities and research organizations, including:

  1. NASA REDDI Program University of Central Florida
  2. Center for Applied Space Technologies
  3. Agronautics, LCC
  4. Sons of Liberty Gun Works,
  5. Jeremiah Pate
  6. Purdue University
  7. Arete
  8. NASA

Despite the failure, this flight marked the third time a suborbital-class rocket stage is reused for a fourth time – with the first two 4th reflights going to Blue Origin’s New Shepard 2 and 3 boosters, respectively.

Exos is – in part – using the SARGE SRLV to test scaled versions of the systems they intend to use in their planned orbital-class rocket.

No timeline has been given for when that orbital rocket might debut.

What is known is that the orbital variant will be capable of lifting 100 kg payloads into Low Earth Orbit.

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