NASA’s Orion spacecraft successfully achieved a contingency landing scenario on Wednesday, returning under just two of its three parachutes. The test – conducted at the U.S. Army’s Yuma Proving Ground in the Arizona desert – was the latest in a series of drops ahead of Orion’s return “for real” during the Exploration Flight Test -1 (EFT-1) mission next year.
Orion Parachute System:
Testing for Orion’s parachutes has been ongoing for many years, initially under the guidance of the Constellation Program (CxP).
The program was achieving notable successes during a period of uncertainty for CxP, before the Orion PTV (first generation) suffered a failure back in 2008, resulting in the vehicle crashing into the ground.
The tests have always involved a boilerplate Orion mock up vehicle and PTV system that consists of numerous additional parachutes, required to drag the test vehicle out of the C-17 aircraft via a sledge or pallet system at 25,000 feet, providing the correct orientation, altitude and speed, whilst also allowing for the pallet to land safely on the ground under its own dedicated parachutes.
During the 2008 failure, the programmer chute failed to inflate after deployment, critically removing the requirement for the vehicle’s descent rate to be slowed down and to be correctly orientated for drogue chute deployment – resulting in the vehicle falling upside down at high speed.
With the increased velocity, when the two drogue chutes deployed, they were ripped off almost immediately due to the higher loads. The three main parachutes then deployed – again subjected to the higher loads – ripping two of them away from the vehicle.
The one remaining parachute valiantly remained attached, but was obviously unable to stop the vehicle crashing to Earth at high speed on its own, resulting in the destruction of most of the test hardware.
Another failure in 2010 was believed to be the fault of the pallet system itself, which allows the test vehicle to slide out of the back of the C-17.
The pallet apparently remained attached to the test vehicle, causing the duo to crash into the ground, again destroying most of the hardware.
However, this test was not officially recorded as a CPAS-related exercise, with the 2008 failure shown as the last CPAS PTV test.
The 2010 parachute test failure occurred during the period Orion was being cancelled by President Obama’s FY2011 budget proposal, prior to being fully reinstated, primarily as a Beyond Earth Orbit (BEO) vehicle, by the 2010 Authorization Act.
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Orion PTV Mark II:
With Orion back into full test operations, teams returned to evaluating the parachute system, this time with a second generation CPAS (L2 Link to CPAS Gen II Hi Res Images).
These changes (L2 Link to Document) included the volume and shape of Main Deployment Bags – which are trapezoidal in design and have a new gusset system.
The improvements were based upon data collected during the failed July, 2008 drop test, along with numerous analytical/computer models relating to what was an ever-changing Orion capsule.
Orion’s design changes were mainly caused by Ares I’s insistence that the capsule should lose mass, a request sent numerous times during the days of the Constellation Program, resulting in fallout on the CPAS team, who noted in the aforementioned presentation that one of the Orion designs they had to work did not even contain the “volume” necessary for the main parachute system.
It is also likely the pallet system will have been modified based on the previous issues.
Numerous tests with the new system have all resulted in successes for the parachute team, with objectives ranging from drop tests that examine how Orion’s wake – the disturbance of the air flow behind the vehicle – impacts the performance of the parachute system, through to examining the effects of one main parachute skipping the first reefing stage.
The latest test was by far the most ambitious, testing how Orion would cope during a return with only two of its three main parachutes.
Dropped from a C-17 aircraft at its highest altitude yet, 35,000 feet above the Arizona desert, one of three massive main parachutes was cut away early on purpose.
Although NASA’s webcast of the event suffered from major technical issues, the patchy coverage did clearly show Orion slowly returning to Earth under just the two chutes.
While engineers had always designed Orion to be able to return a crew back safely under two chutes, this was the first opportunity to study how one parachute pulling away in mid-flight might affect the remaining two.
“We wanted to know what would happen if a cable got hooked around a sharp edge and snapped off when the parachutes deployed,” said Stu McClung, Orion’s landing and recovery system manager at Johnson. “We don’t think that would ever happen, but if it did, would it cause other failures? We want to know everything that could possibly go wrong, so that we can fix it before it does.”
While the tests are ultimately designed to complete the safe conclusion of the first crewed mission during Exploration Mission -2 (EM-2) in 2021, the first return from space for Orion is just a year away.
EFT-1 will mimic Orion’s return from a Beyond Earth Orbit (BEO) mission, proving a critical test for both the Thermal Protection System (TPS) and the parachutes. Orion will splashdown in the Pacific Ocean.
“The closer we can get to actual flight conditions, the more confidence we gain in the system,” said Chris Johnson, project manager for the Orion capsule parachute assembly system at NASA’s Johnson Space Center in Houston.
“What we saw today – other than the failures we put in on purpose – is very similar to what Orion will look like coming back during Exploration Flight Test-1’s Earth entry next year.”
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