Second Hot Fire Test NET 21 Feb, As Artemis-1 Booster Stacking Continues

Stacking of the dual five-segment Strong Rocket Boosters (SRBs) continues within the Car Meeting Constructing (VAB), as NASA zeroes-in on late February for its second Sizzling Hearth Take a look at. Photograph Credit score: Jeff Seibert/AmericaSpace

Following last month’s brief ignition of four shuttle-era RS-25 engines at the base of the Core Stage for the first Space Launch System (SLS), NASA has introduced that it’s going to execute a second Sizzling Hearth Take a look at as quickly because the week commencing Sunday, 21 February. The 212-foot-tall (64.6-meter) Core Stage has for greater than a 12 months resided within the B-2 Take a look at Stand at NASA’s Stennis Area Heart (SSC) in Bay St. Louis, Miss., where it is being put through an extensive, eight-step “Green Run” campaign to make sure its purposeful and operational readiness for launch.

Within the meantime, contained in the cavernous expanse of the Car Meeting Constructing (VAB) on the Kennedy Area Heart (KSC) in Florida, stacking of the twin five-segment Solid Rocket Boosters (SRBs) is nearing completion.

Video Credit score: AmericaSpace

Following its arrival within the B-2 Take a look at Stand early final 12 months, the Core Stage was put via a punishing regime of 5 purposeful checks between January and September. These have been completed with exceptional velocity in view of the worldwide march of the COVID-19 coronavirus pandemic and a number of pure predators within the type of Hurricanes Marco, Laura and Sally final summer time and Hurricane Zeta last fall.

This work validated fashions to function the large rocket’s Steerage, Navigation and Management (GNC) techniques, checked out its avionics, examined its security techniques, evaluated command management operations for its Most important Propulsion System (MPS) and operated its Thrust Vector Management (TVC) and hydraulics.

Like a bathe of sparklers, the hydrogen burn-off igniters served to clear unburned hydrogen from beneath the RS-25 engines. Photograph Credit score: NASA

Following the completion of the purposeful checks, three operational checks got underway in October, simulating a full SLS countdown, loading greater than 733,000 gallons (3.Three million liters) of liquid oxygen and hydrogen propellants into the Core Stage—referred to as the Moist Gown Rehearsal (WDR)—and test-firing the 4 RS-25 engines for a full mission period of over eight minutes. This “Sizzling Hearth Take a look at” lastly obtained underway on 16 January, but was cut short and the engines commanded to shut down after only 67.2 seconds.

It was later revealed by NASA that the untimely shutdown was triggered when one engine exceeded its extremely conservative check parameters. Unique plans known as for the quartet of engines—all of that are refurbished Area Shuttle Most important Engines (SSMEs), with over 1.1 million seconds’ value of “burn-time” and a complete of 25 shuttle missions to their credit score—to be fired for as much as 485 seconds, approximating as carefully as attainable the situations that they may encounter throughout the SLS rocket’s raging climb to orbit.  

Billowing clouds of steam pour from the B-2 Take a look at Stand at NASA’s Stennis Area Heart (SSC) in Bay St. Louis, Miss., throughout 16 January’s first Sizzling Hearth Take a look at. Photograph Credit score: NASA

A minute into the Sizzling Hearth Take a look at, the pre-planned gimbaling of the engines beneath TVC management obtained underway. “We started to undergo an aggressive gimbal profile of all 4 engines,” defined SLS Program Supervisor John Honeycutt of NASA’s Marshall Area Flight Heart (MSFC) in Huntsville, Ala. Duty for gimbaling the engines fell to the TVC actuators, every of which is powered by a Core Stage Auxiliary Energy Unit (CAPU).

At about 61 seconds into the Sizzling Hearth Take a look at, CAPU-2—which serves the Core Phases’ No. 2 engine—detected low hydraulic fluid ranges and after a sequence of verification checks over the following two or three milliseconds to validate the studying, correctly shut itself down. The opposite three CAPUs momentarily elevated their hydraulic pressures to 105 % to compensate for the evolving state of affairs, earlier than CAPU-2 commanded the Core Stage flight laptop to close down the opposite engines. This was executed safely and satisfactorily.

All 4 RS-25 engines had shut down safely by 67.2 seconds into the Sizzling Hearth Take a look at. Photograph Credit score: NASA

In summing up the habits of Core Stage techniques throughout the check, NASA famous that on a “actual” launch the CAPU margins would have been loosened and CAPU-2 would have continued to perform usually. It was careworn by Mr. Honeycutt that parameters have been deliberately set at extremely conservative ranges to greatest defend the Core Stage, which is, in fact, not merely a check article, however precise flight {hardware}.

The Sizzling Hearth Take a look at was meant to amass check knowledge in help of 23 detailed verification goals, with the 16 January firing having “met the objectives for a quantity” of those necessities, “comparable to these associated to actions previous to engine ignition”, and having “partially met the objectives for a number of extra” goals. 5 important successes included transitioning to the automated launch sequence (operated by the Core Stage flight laptop and Inexperienced Run software program), finishing the terminal countdown sequence, pressurizing the propellant tanks, firing the 4 RS-25 engines at a 109-percent energy stage and working the TVC system for efficient steering functionality.

The ten segments for Artemis-1’s twin five-segment Strong Rocket Boosters (SRBs) arrived by rail on the Kennedy Area Heart (KSC) in June. The long-lasting Car Meeting Constructing (VAB) is clearly seen within the background. Photograph Credit score: NASA

“They’re wanting on the check knowledge to find out if the parameters must be modified,” NASA’s Tracy McMahan advised AmericaSpace. “It’s actually the best way the parameters triggered the shutdown by the flight computer systems that can also be being evaluated. Principally, the flight software program is programmed that if these two parameters transcend these redlines, it shuts down the check. That is the management logic of the software program. It’s pretty simple to regulate this due to the best way the software program is written. They won’t modify the parameters past what they suppose is the correct amount to nonetheless defend the stage and the engine. They realized rather a lot about how the stage operates throughout the first sizzling fireplace that they didn’t know earlier than the primary sizzling fireplace; this knowledge helps them decide learn how to set these parameters, so that they nonetheless defend the core stage.”

It was additionally famous that the Core Stage may be loaded with propellant and pressurized a complete of 22 instances, with two “cryogenic loading cycles” having been accomplished to this point: final fall’s WDR and the primary Sizzling Hearth Take a look at. “Earlier than Inexperienced Run testing started, SLS had allotted 9 cryogenic cycles for testing at NASA’s Stennis Area Heart,” the company defined, “and has used two of these throughout the Sizzling Hearth and Moist Gown Rehearsal, with seven cryogenic cycles remaining for added testing.”

Certainly one of Artemis-1’s aft skirts is moved from a check cell within the Booster Fabrication Facility (BFF) in June 2020. Photograph Credit score: NASA

The remaining 13 cryogenic cycles are being held in reserve for the Core Stage’s position within the bold Artemis-1 mission, to protect in opposition to the potential of a number of fueling campaigns in help of a number of launch makes an attempt, in addition to a pre-launch WDR “and different actions that require propellant loading and tank pressurization”.

Simply final week, NASA and Core Stage prime contractor Boeing announced their intent to conduct a second Hot Fire Test “as early because the fourth week in February”, revealing that doing so “would pose minimal threat” to the {hardware}, while yielding priceless certification knowledge forward of Artemis-1.

The aft skirt and aft section for one among Artemis-1’s twin Strong Rocket Boosters (SRBs) stands tall throughout stacking operations final fall. Photograph Credit score: NASA

“Conducting a second Sizzling Hearth Take a look at will enable the workforce to repeat operations from the primary Sizzling Hearth Take a look at and acquire knowledge on how the Core Stage and the engines carry out over an extended interval that simulates extra actions throughout the rocket’s launch and ascent,” it was defined. Preparations for the second check together with drying and refurbishing the RS-25 engines, tending to minor Thermal Safety System (TPS) repairs and updating conservative management logic parameters on the flight laptop.  

“These RS-25 engines flew on a number of shuttle flights and they’re designed to be fired greater than as soon as,” NASA’s Tracy McMahan advised AmericaSpace. “After each firing, they’re utterly dried with nitrogen. This ensures they’re clear and contaminant-free. There are a number of different issues have must happen, together with minor Thermal Safety System repairs. They’re additionally wanting on the parameters, comparable to those that triggered the early shutdown, and seeing if the info reveals these may be much less conservative for the second check. Then they must replace the Inexperienced Run Utility Software program with the brand new parameters.

The sheer measurement and scale of the five-segment SRBs, which can stand 177 ft tall (53.9 meters) when absolutely stacked, is clear on this view from earlier this 12 months. Photograph Credit score: NASA

“They are going to be working all these actions in preparation for the second sizzling fireplace. They’ll know extra after a Take a look at Readiness Evaluate that ought to happen subsequent week. We are going to attempt to have one other media telecon after that to debate what they’re doing and the trail ahead.”

Within the meantime, the second main element for Artemis-1—a pair of five-segment Strong Rocket Boosters (SRBs), constructed by Northrop Grumman Corp.—were delivered from Promontory, Utah, to KSC, last June for processing. In readiness for stacking, the boosters’ large aft “skirts” were moved from the check cell in KSC’s Booster Fabrication Facility (BFF) to the Rotation, Processing and Surge Facility (RPSF) for momentary storage.

Video Credit score: NASA

Precise stacking preparations obtained underway in comparatively quick order, with the initial “pinning” of the aft skirts onto the boosters’ aft segments. Late final November, the aft-segment hardware was transferred from the RPSF to Excessive Bay Three of the cavernous VAB and in January the center-aft segments were installed atop them. Yesterday, on the anniversary of the lack of shuttle Columbia and her STS-107 crew, NASA introduced that the middle segments had additionally been stacked, as booster meeting handed the midway level.

With the second Sizzling Hearth Take a look at focused for no prior to the week of 21 February, the items of SLS {hardware} for Artemis-1 are anticipated to fall into place later this spring. Assuming that each one goes effectively—and however a month-long delay—NASA anticipates the supply of the Core Stage to KSC in March, nevertheless it stays to be seen what long-term impacts this supply schedule might need on the focused November launch date. “There are various different actions that have an effect on the launch date,” Ms. McMahan defined. “We shall be taking a look at these actions and attempting to realize some efficiencies to guard the launch date.”

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