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SLS RS-25 Engine Test Aborted After Engine Bursts Into Flame
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Photo: NASA

SLS RS-25 Engine Test Aborted After Engine Bursts Into Flame

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MISSISSIPPI – December 14, 2018

On Wednesday, the test RS-25 engine for the superheavy launch SLS designed for manned missions to Mars ended in failure: Approximately 35 seconds after switching on, the base of the engine burst into flame and was shut down. The engine was shaking violently shortly before the shutdown.

The RS-25 engine test was being conducted on the A-1 Test Stand at Stennis Space Center near Bay St. Louis, Mississippi, where the agency is testing engines to help power its new Space Launch System (SLS) rocket.

Typical tests run 8 minutes and 20 seconds, the amount of time the engine must fire to power the rocket from launch into space. Three RS-25 engines would have to fire for 10 minutes and 50 seconds to burn up propellant and power the rocket into orbit, if the fourth shut down early during an SLS launch. The longer time also allows operators to schedule and meet more performance objectives during a test.

NASA reported regarding the accident: “On December 12 at 3:24 pm. (CST), a scheduled RS-25 engine test at NASA’s Stennis Space Center experienced an early shutdown. Post-test securing and processing are in progress.”

The hot fire was also the seventh on this engine in a current series of acceptance tests for RS-25 engine controllers that will be used on future SLS flights. The new controller is a key component of recent engine modifications. It operates as the brain of the engine, helping it to communicate with the rocket and controlling engine operation and internal health diagnostics. The hot fire also featured continued testing of two innovative engine components – a 3D-printed pogo accumulator to dampen pressure oscillations that can cause flight instability and a main combustion chamber (MCC) fabricated using a new hot isostatic pressing (HIP) bonding technique that saves considerable time and money by over 50% from the amounts for the heritage Space Shuttle Main Engine (SSME).

The MCCs for production restart engines use HIP bonding to form the jacket around the liner. “You’ve got the liner and you’ve got the jacket separately, you put that into the furnace and that hot, high-pressure allows you to make that bond between the liner and jacket and that’s what we’re utilizing now on the MCC,” Dan Adamski, RS-25 Program Director for Aerojet Rocketdyne said in a recent interview.

On Nov. 15, operators fired development engine No. 0525 to a 113% thrust level for 60 seconds during the full-duration 650-second test, marking only the second time they have achieved the highest RS-25 power level. Engineers first fired development engine No. 0528 to that level during a February test at Stennis.

Four RS-25 engines will help power SLS at launch, supplying a combined 2 million pounds of thrust and working in conjunction with a pair of solid rocket boosters to provide more than 8 million pounds of thrust. Originally designed more than 40 years ago to provide a specific power level categorized as 100% thrust, the RS-25 version of the space shuttle main engine has been upgraded to operate at 111% of its original power, with the 113% hot fires at Stennis allowing operators to test a margin of safety. NASA has been testing RS-25 modifications and flight engines at Stennis since January 2015 in preparation for the Exploration Mission-1 (EM-1) and Exploration Mission-2 (EM-2) flights of SLS. EM-1 will test the capabilities of the new rocket and will carry an uncrewed Orion spacecraft into space beyond the moon. EM-2 will be the first flight to carry humans aboard the Orion spacecraft, returning astronauts to deep space for the first time in more than 40 years. This missile should be the most load-lifting in the last 40 years as well.

The failed test was supposed to mark the fourth time an RS-25 engine has been fired for the longer duration. RS-25 tests continue NASA’s progress toward Exploration Mission-1, where the new rocket will send an Orion spacecraft around the Moon and back to test critical capabilities needed to carry astronauts farther in space than ever before, and eventually to Mars. On Exploration Mission-2, SLS will carry astronauts aboard Orion on a return to deep space. Prior to those flights, NASA will test the SLS core stage on the B-2 Test Stand at Stennis. RS-25 tests at Stennis are conducted by a combined team of NASA, Aerojet Rocketdyne and Syncom Space Services operators. Aerojet Rocketdyne is the RS-25 prime contractor. Syncom Space Services is the prime contractor for Stennis facilities and operations.

A fault in the engine, the details of which are not disclosed, may affect the timing of the first launch. While the first unmanned flight is planned for mid-2020, manned – 2023.

Unfortunately, this is not the first time an RS-25 engine test has experienced an early shutdown.

On August 14, the test of the Development Engine 0525 (E5025) aborted early due to what is understood to be a “facility issue”, although all the test objectives were achieved, NASASpaceFlight.com reported. Information acquired later in the day noted they did get to 111% RPL before the abort and that the objectives were achieved.

“Early cut issued at 319 seconds by test conductor due to LH transfer initiation issue,” noted L2 information into the abort. Further inquiries pointed to this being related to a facility issue – as was the case with a previous test abort in 2016.

Aerojet Rocketdyne was awarded a contract by NASA in late 2015 to restart production of the RS-25, formerly known as the Space Shuttle Main Engine (SSME). The SLS Program has sixteen engines left over from the Space Shuttle era, which will be expended on the first four launches.

Author: USA Really