The Orion Program has successfully conducted another parachute drop test over the U.S. Army’s Yuma Proving Ground in the Arizona desert, testing failure scenarios with the Drogue and Main parachute system. Wednesday’s test comes after a recent safety briefing warned of crew health concerns relating to a pendulum effect when the Orion spacecraft is under her parachutes.
Orion Drop Test:
Orion is back into training as she prepares for her second trip into space as part of the Exploration Mission -1 (EM-1) flight in 2018.
The spacecraft conducted her first mission in space during last year’s Exploration Flight Test -1 (EFT-1) mission, lofted uphill by a Delta IV-H. In 2018, Orion will be launched by her long-term partner, SLS.
For the test series in Arizona, a boilerplate Orion spacecraft is dropped out of the back of a plane, following a test process that has been conducted since the early days of the Constellation Program (CxP).
The tests use a Parachute Test Vehicle (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 altitudes ranging from 25,000 to 35,000 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.
The test series has not been without its failures.
The Orion PTV (Parachute Test Vehicle – first generation) suffered a failure back in 2008, when 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.
This failure resulted 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 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 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.
Testing since then has proceeded with numerous successes, as Orion found her new role as an exploration vehicle, 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.
Tests on how Orion would cope during a return with only two of her three main parachutes deployed was again the subject of Wednesday’s test. However, this test was the most ambitious to date.
With the C-17 aircraft 35,000 feet above the drop zone, the test included a scenario in which one of Orion’s two drogue parachutes, used to stabilize her in the air, does not deploy, and one of her three main parachutes, used to slow the capsule during the final stage of descent, also does not deploy.
The “riskiest test ever conducted by Orion” was deemed a success and will now provide data to engineers that they will use to qualify Orion’s parachutes for missions with astronauts.
Notably, the system is designed to provide the End Of Mission (EOM) success to a crew’s trip into space, requiring a large amount of evaluation to ensure that goal – of bringing the crew to safe landing in the ocean – is accomplished.
The recent Aerospace Safety Advisory Panel (ASAP) meeting was provided a program status update that included an issue called ‘pendulum risk’.
Notably, that issue relates to a scenario that was tested on Wednesday, where one of the three Orion parachutes fails. The ASAP members were told there can be a pendulum effect where there is oscillation of the suspended Orion spacecraft under the parachutes.
It is believed that under certain situations, the landing loads could present a hazard in terms of crew health. However, the Orion team noted they have a good understanding of the issue via extensive analysis and has found that the way to mitigate this risk is reduce the deploy altitude for the main chutes from 8,000 feet to 6,800 feet.
The ASAP expects to be updated on the analysis in future meetings, including information to understand “how that was decided, what the margins were, and why 8,000 feet was the deploy altitude for the parachutes to begin with if 6800 feet is thought to be acceptable now,” per the meeting’s minutes.
Orion will continue to enjoy drop tests in Arizona in the run up to EM-1.
(Images: Via L2 and NASA). (To join L2, click here:http://www.nasaspaceflight.com/l2/)