14.07.2021

NASA, Northrop Grumman designing new BOLE SRB for SLS Block 2 vehicle

NASA’s Space Launch System (SLS) program and booster element prime contractor Northrop Grumman are developing an upgrade to the current Solid Rocket Boosters (SRBs). The SLS Booster Obsolescence and Life Extension (BOLE) program is in the detailed design phase prior to firing its first ground-test development motor in 2024, followed by a preliminary design review for the boosters that will inaugurate the SLS Block 2 vehicle.

The new solid rocket motor design retains the form and fit of the current motor, but incorporates modern production technology, composite cases, and a new solid propellant formula. NASA SLS and Northrop Grumman are working to integrate the new design with the SLS vehicle and increase performance to Congressionally-mandated levels while minimizing impacts to the design and operations of other flight hardware and launch processing infrastructure.

BOLE upgrade replaces current booster originally designed for Ares I

The BOLE program is a joint effort between NASA and Northrop Grumman to develop a new solid rocket booster design with modern production and manufacturing processes. The new design is intended to replace the current SLS boosters that are based on a five-segment solid rocket motor (RSRMV).

The RSRMV is an evolution of the Space Shuttle Redesigned/Reusable Solid Rocket Motor (RSRM) and was originally designed to be the first-stage of the Constellation Program’s Ares I Crew Launch Vehicle. After Constellation was cancelled, the motor was adapted from its single-stick, first stage application for Ares I to the dual boosters that flank the large Core Stage for SLS.

The current booster uses Shuttle flight hardware and technologies that are becoming obsolete. SLS is an expendable launch vehicle, so in addition to the technology obsolescence, launches will also consume the remaining inventory of Shuttle SRB flight hardware. “When the Shuttle program came to an end, it was decided as the SLS program was starting to ramp up that the project would save enough hardware to give us eight flight sets of the large, structural hardware, the case segments and that sort of thing,” Dave Reynolds, NASA’s Deputy Program Manager for the SLS Booster Element Office, said in a June 25 interview with NASASpaceflight.

Credit: Northrop Grumman.

(Photo Caption: An overview of changes in the new BOLE SRB design when compared to the current design. The new design retains the form and fit of the current boosters, but makes the extensive changes summarized in this Northrop Grumman presentation slide.)

“[We also knew] that at the end of those eight flights we would need a follow-on program that would give us a booster with a minimum of the same capability, but [we] may as well take advantage of the technological advances that have taken place in rocketry over the last 30 years [to] be able to give us a safer, more robust, and more capable booster.”

NASA is developing two major upgrades to the initial operating capability provided by the Block 1 configuration. The Block 1 vehicle combines two RSRMV-based SRBs and a liquid hydrogen, liquid oxygen Core Stage with United Launch Alliance’s Delta IV Heavy second stage as an essentially off-the-shelf, in-space stage called the Interim Cryogenic Propulsion Stage (ICPS). 

The first upgrade that would be phased in is Block 1B, which replaces the ICPS with an in-house Exploration Upper Stage (EUS) that is, like BOLE, tailored to SLS. EUS is currently planned to begin flying on the fourth SLS launch. Adding the BOLE boosters to the Block 1B vehicle is now viewed as the Block 2 configuration. 

An Advanced Boosters competition was part of the initial development roadmap during the first few years of the SLS Program, but was set aside in part due to the budget constraints during that time. The new BOLE motor is being designed to better integrate with SLS Block 1B and at the same time to increase the overall vehicle performance.

Edit: NG later e-mailed noting the mention of the “Advanced Booster competition” should no longer be referenced and to “define Block 2 simply as the incorporation of BOLE”.

“By focusing on ballistics and changing the propellant to something more modern and higher performing, that necessitates that you have a different nozzle because you have different ballistics, different materials that are coming through. So you need an upgrade on your nozzle material,” Reynolds explained.

“By upgrading your nozzle material and your ballistics you need a different and more robust case and of course they’ve made tremendous strides in composite, carbon-fiber wound filament cases over the past 30, 40 years. And so you are taking advantage of the strengths of the composites. Once you take those three components you also need a new way to attach to the booster structures because it’s a different load path that the booster will set up at that point.”

“If you’re going to redesign that, you may as well optimize it for what the SLS mission is, so you change your attach points and then [when you] put all that together you’re going to have a different TVC [thrust vector control] system and avionics system to be able to drive that,” he added. “So basically the whole booster is an upgrade to a more modern set of technologies, taking advantage of everything.”

In addition to changing the connections from the BOLE boosters to the SLS Core Stage, the new design also moves away from the Shuttle-style connections to the launch platform. “The current booster has a heavy footprint at the point where it attaches to the Mobile Launcher, and that’s because it’s Shuttle heritage,” Reynolds said.

“When Shuttle fired off it’s engines a few seconds before the boosters fired, the whole Shuttle ‘twanged.’ It moved off of center and then it kind of sprung back. Well, that doesn’t happen on SLS.”

“That heavy footprint that bolted the Shuttle down to the pad is no longer necessary,” Reynolds noted. “If you don’t need that heavy footprint attached to the Mobile Launcher any more, then you have a lot more ability to lighten up your aft skirt so that you leave some of that mass on the ground and give yourself some more payload capability for the rocket.”

The new TVC system in the BOLE design is an electric, battery-powered system, which will replace the current Shuttle heritage system that is powered by toxic hydrazine fuel. “Similarly to the motor case structures, we saved several of the Shuttle hydrazine-driven TVC systems for the first eight flight sets, but after that we were going to have to go back to the assembly line, many of which have been closed down for 20 years or more,” Reynolds noted.

“[We could] fire them back up, or we could move to a more state-of-the-art, modern design. And since the OmegA program had already done the pathfinding for us on the eTVC (electric TVC) system, we were able to easily take advantage of that. That has the additional benefits of giving us the possibility of eliminating a hazardous material from the booster: the hydrazine.”

Credit: NASA.

(Photo Caption: Graphic comparing the different versions of SLS in development. The SLS Block 1 Crew configuration will fly three Orion lunar missions before being superseded by the Block 1B Crew vehicle. Both Block 1B and Block 2 still have Cargo configurations in design/development, but work on a Block 1 Cargo vehicle was discontinued after the Europa Clipper spacecraft was finally taken off the SLS manifest due to compatibility and availability issues.)

“Nobody likes working with hydrazine if they can avoid it, and so by switching over to an electric, battery-driven design you get to eliminate some of those challenges with the con-ops [concept of operations] that we’ve had to deal with all throughout the Shuttle days and these early days of SLS,” he added.

The new design also uses a different propellant mix from the Shuttle solid motors, which allows more of the higher-impulse propellant to be stored. “The booster itself is heavier, but it’s primarily heavier because it has more propellant in it,” Mark Tobias, Northrop Grumman’s Deputy Chief Engineer for the SLS Booster Element, said.

“We were able to pack more propellant [in, because] the propellant that we’re using is a higher density than the current propellant. Composite cases are obviously much lighter than steel cases for a constant set of design requirements, so we were able to go increase the internal chamber pressure of the motor to provide more thrust for the same weight.”

“We allowed ourselves to go [up] to about a two, three hundred psi (pounds per square inch) increase in [chamber] pressure with no mass penalty because we went to composite cases,” Tobias explained. “So the boosters actually weigh more but it’s because they’re carrying more propellant than the current ones.”

The thrust trace for the BOLE motor is also tailored to the SLS vehicle compared to the Constellation/Ares I-designed RSRMV. Solid rocket motors may not have the fine throttling control of some liquid engines, but their thrust is designed to change for different phases of flight.

The thrust trace is a plot of thrust versus time showing how the motor performance is designed to vary during the action time from ignition to burnout. Tailoring the the extra impulse with the BOLE motor to the SLS vehicle and ascent trajectory generated a lot of discussion.

Credit: Northrop Grumman.

(Photo Caption: A NASA slide comparing the thrust trace of the SLS Block 1B and Block 2 and exergy performance analysis of the two vehicle configurations. The BOLE motor thrust trace is tailored to the SLS flight profile, both improving payload performance and reducing operational constraints.)

“When we were designing the thrust trace, max dynamic pressure and actually the time at which max dynamic pressure occurs was a topic of intense discussion,” Tobias said. “There was a tremendous amount of design iteration around the various different Mach number and dynamic pressure regimes, and ultimately the Booster [element] working with the [SLS Program] vehicle design team settled on a design constraint where we actually constrain the dynamic pressure as a function of Mach number.”

“Essentially, what that constraint is, is it tells the booster you can only put so much impulse in the transonic portion of vehicle flight. So we essentially detuned the booster in that transonic portion of flight ,and then we tuned it back up in the later portions of flight in order to get performance back,” he added. “So dynamic pressure was a primary driver in the thrust trace design. It took us quite a bit of effort, several months of design iteration to get that right.”

For SLS Block 1 launches, the four Aerojet Rocketdyne RS-25 engines in the Core Stage could have a busier throttle profile during the first stage of flight than they did as a trio during Space Shuttle launches. During the first stage of Shuttle launches while the SRBs were firing, the three Space Shuttle Main Engines (their original name) would throttle down for several seconds in the transonic, maximum dynamic pressure (Max-Q) portion of ascent.

On early SLS launches, the engines may be asked to nominally throttle down around Max-Q in addition to a mandatory throttle-down around the time of SRB separation to reduce loading on the forward Core Stage-Booster attach points as the solid motor thrust tails off.

In addition to the heritage RSRMV thrust trace, the heritage Shuttle SRB case structures were designed for the Shuttle-scale forces. The heritage structures for the forward and aft assemblies of the current SLS boosters were reinforced, but throttling the RS-25 engines is still necessary in places during first-stage ascent to keep the loads within limits.

The new BOLE motor structures and thrust trace are designed to reduce the liquid-engine throttling demands. “One of the goals of the BOLE program was to get rid of some of those operational constraints. So with the BOLE booster, the RS-25s don’t have to throttle at all during first stage portion of ascent,” Tobias noted.

“Some of the structural reasons that the current Block 1 vehicle throttles are eliminated by the BOLE because those structures that carry the primary load path have all been redesigned. They are designed to this specific load, so there’s no reason to require the engines to throttle any more. And of course that’s a performance gain as well.”

The liquid engines will still have to throttle late in the ascent, well after the boosters separate, to maintain acceleration limits prior to their shutdown.

Borrowing from OmegA technology development, but tailoring for SLS

Some basic aspects of the new BOLE motor design draw on technology development that Northrop Grumman was working on as a part of the OmegA launch vehicle program. Northrop Grumman received an Air Force Research, Development, Test and Evaluation (RDT&E) award in October 2018 to develop the OmegA rocket concept as a part of the U.S. government’s National Security Space Launch (NSSL) program.

Production of the first development units for the multi-stage, solid-propellant vehicle occurred at the company’s Promontory facility in northern Utah, using some of the same infrastructure as the SLS boosters, along with more modern manufacturing technologies. Although the OmegA Common Booster Segment (CBS) concept was not selected in 2020 to continue development, the SLS BOLE motor draws on some of the OmegA technology development and testing.

“The BOLE booster takes advantage of a couple of things,” Tobias said. “One, a lot of qualification work that was done at the hardware and design level.”

“For example, we’re using the same carbon-fiber and resin system for the cases as OmegA did. We’re using the same electric TVC system that CBS and OmegA did, except we’re upgrading it to be single-fault tolerant where the CBS/OmegA system was zero-fault tolerant.”

Credit: Northrop Grumman.

(Photo Caption: The aft skirt for a ground test of the OmegA first stage motor is seen in April 2019 during assembly activities at Northrop Grumman’s Promontory facilities in northern Utah. The BOLE design is taking the electric TVC equipment shown, such as the nozzle gimbaling actuators seen prominently at the two o’clock and four o’clock positions here, and adding the additional fault-tolerance redundancy required in a human-rated launch vehicle.)

“We’re using essentially the same propellant formulation,” Tobias added. “It’s slightly modified for different reference burn rate because the requirements for our booster are different than theirs, [because OmegA was to fly] significantly different kinds of payload missions. But by and large the TVC system is being ported over. So a lot of the major elements of the booster are very, very similar to CBS/OmegA program.”

“The second way we leverage that program is through infrastructure,” Tobias continued. “So the case winding machines, the case machining centers, the ovens that cure the case, the machinery that winds the insulation into the case, the facilities associated with that, these are all infrastructure that were invested in by Northrop Grumman for CBS/OmegA, and they’re directly utilized by the BOLE program.”

As Tobias noted, SLS requires at least single-fault tolerance because it is a human-rated launch vehicle. The electric TVC system adds a third command and control “string” to power the rock and tilt actuators for the BOLE booster nozzle.

“There’s three independent avionics and command and power strings for this system,” Tobias said. “The best way to illustrate this is the [OmegA] CBS actuator has two motor pump assemblies that provide the hydraulic power to drive the actuator. We’re adding a third so we have those three complete, independent strings, both from a command standpoint at the avionics end and at the end-effector end of the architecture at the actuator level.”

The BOLE booster is also being designed as an upgrade to the existing SLS Block 1 vehicle, as opposed to the clean-sheet concept of operations for OmegA. During design, Northrop Grumman and NASA have prioritized integration with SLS launch operations and flight operations.

An example of this is the nose cones for the boosters. Studies were conducted on different shapes than the current vehicle, but the program made the choice to retain the existing style. “We looked at that very early on and traded around some different concepts. 

Ultimately we brought the different concepts to the vehicle, particularly the Chief Engineer for the vehicle,” Reynolds noted. “His desire was to minimize any perturbations to the system for future integration, and so currently the design that we’re holding right now is to maintain a conical nose design.”

Credit: ESA/Arianespace

(Photo Caption: A potential design change to the BOLE SRBs considered but ultimately decided against would have seen the SRB nose cone assemblies altered to more closely resemble those used on the Ariane 5. In the end, NASA and Northrop Grumman decided to keep the conical shaped nose assembly design that currently flies with SLS.)

The BOLE motor is, like OmegA, a segmented design with the same diameter as the Space Shuttle RSRM cases; however, the BOLE motor retains the same five segments and dimensions as the SLS RSRMV, so the composite cases are shorter than the OmegA design.

“The CBS segments were actually longer than the BOLE segments,” Tobias said. “The OmegA rocket was four segments instead of five, and the reason ours are a different length is because we want to minimize the integration impact to the existing SLS Core Stage and launch vehicle to the greatest extent possible. So we’re constraining ourselves to some of the major interfaces so that the rest of the vehicle doesn’t have to redesign around us.”

“For example, the platforms in the VAB. They have some [capability] to move platforms to different heights and different locations. But say [theoretically] we went to six segments, that would be a significant impact to the VAB beyond what they could accommodate.”

“So we’ve tried to go maintain those major interfaces both with the vehicle and with the ground,” Tobias added. “One of the beauties of composite cases is you’re not tied to a certain piece of tooling or a certain forging or that type of stuff. You can change the dimensions however you like. Geometry is much more flexible when you’re dealing with composite cases.”

“Now for the ground we have changed where the booster actually mates to the Mobile Launcher, and we did that because the Block 2 vehicle will be launching from a different Mobile Launcher than the Block 1 vehicle and so we had the design space to go change things without any negative impacts.”

While the new boosters will retain a similar outer mold-line (OML) to the current boosters, the separation system is another area that changes. “The separation dynamics of the Block 2 vehicle are different due to the higher performing boosters, the RS-25s running at two-percent higher power level, and the overall mass and aero (aerodynamics) of the vehicle is different because obviously it’s a larger vehicle than we have,” Tobias explained.

(Photo Caption: A composite of computer-aided design (CAD) graphics showing the design and layout of the aft BOLE attachment to the Core Stage. The graphics also depict the different aft Booster Separation Motor arrangement on the BOLE booster’s aft skirt.)

“So those changes in aerodynamics, those changes in the axial force that the vehicle is experiencing takes you to a different design point for the separation algorithm, which results in changes to the number and location of the BSMs.”

As during Shuttle, and carried over to SLS, groups of smaller solid rockets called Booster Separation Motors (BSM) fire to push the empty SRB cases away from the Core Stage when the bolts connecting them are pyrotechnically severed. In the current separation system, groups of four BSMs are located in the nose cone at the forward end and the aft skirt on the aft end.

The new system of BSMs was designed for the different way the boosters will be attached to the Core Stage and different conditions at SRB separation.

“We were able to optimize with the new attach schema with the vehicle and we were able to optimize the separation algorithm, so we actually have fewer BSMs than the current configuration,” Tobias said. “We just finished that trade study and have now baselined a new architecture. So we actually have three BSMs in the forward end and two in the aft end, and they’re oriented differently. Their net force vectors are pointing in a different direction than the current booster.”

The attachments between the Core Stage and the new boosters are also changing from the old design. “One of the integration changes we’ve made [is to] the aft attach,” Tobias said. “We’ve actually borrowed that design from the Titan program. It provides us increased clearance during separation because it eliminates, in particular, the diagonal strut that is on the Block 1 configurations, and so it gives you a more robust design space for separating the boosters from the Core Stage.”

“Also it’s a simpler design,” Tobias added. “The hardware is not as complex, so we kind of borrowed from our historical design practices in other programs and it’s a fairly minimal change to the Core Stage as well. So we did those things because we’re trying to increase the ease of integration, we’re trying to increase our margins where we can. And if we can make things simpler and more robust things get cheaper in the long run.”

The new SRB design would not be fully needed until the ninth SLS launch, but some elements of the Shuttle SRB inventory have been in storage for over a decade since the final Shuttle flight. As a part of preparing for the obsolescence of some critical elements, the BOLE program is also evaluating possible backup capabilities to support the legacy design.

Between NASA and Northrop Grumman, the SLS Booster element is planning to conduct an experiment on the next full-scale ground test motor for the current RSRMV design, called Flight Support Booster-2. “One secondary objective that we’re targeting, and it looks like we’ll be able to make this happen, is we are actually going to put the OmegA version of the electric TVC system on that booster,” Reynolds said.

“I don’t want to give the wrong impression that that means we’re planning on putting the eTVC system on the first eight flight sets. That’s not the current plan, but like I said, a lot of that hardware that was carried over from Shuttle [and] some of it [has] still not been fully inspected within its storage containers.”

First development motor firing planned for 2024

For the new BOLE motor design, the program is moving towards its first full-scale ground test firing. “Our focus is primarily on what we call Development Motor-1 or DM-1, which will be the first static test motor. And the major objective of that static test motor is to get direct measurement of the actual thrust produced by the booster and to make sure that it is behaving as we designed it and as we intended it to,” Tobias said.

“So motor performance is the major objective out of that test; of course there’s also going to be a lot of component objectives as well but that’s the main focus now. We’ve moved from conceptual design, we’re out of that phase. We’ve made all of our major architecture decisions, and now we’re actually in the detailed design phase for the static test motor.”

“And on the heels of the [first] static test motor will be the preliminary design review,” he added.

Credit: NASA.

(Photo Caption: A NASA presentation slide outlining plans for the two major upgrades from the initial operating capability that will fly on the Artemis 1 mission. The initial Block 1B flight would use the fourth and final set of SLS-adapted Space Shuttle Main Engines; thereafter, the intermediate configuration will begin flying new RS-25 production restart engines. Finally, the BOLE “enhanced performance” booster would enter service on the ninth SLS launch.)

A total of three development motors and two qualification motors would be fired during development prior to the new booster’s first flight. “We have three development motors, our DMs, that are planned and that would be followed by our CDR (Critical Design Review),” Reynolds said.

“Then that would be followed by two qualification motors, followed by our DCR, design certification review, and then it would be a qualified system. That’s a pretty typical development plan for a booster.”

“That’s essentially what we did with the RSRMV, so we’re kind of following that same path,” he added. “And as far as timing goes, the schedule lays us out for being able to accomplish that first DM test in summer of ’24.”

In parallel with detailed design of the BOLE motor and booster system, design analysis of the integrated SLS Block 2 vehicle combining the EUS and BOLE upgrades to the Block 1 configuration is also underway. “DAC-1 (Design Analysis Cycle-1) is the current design cycle,” Tobias said. “Northrop Grumman is currently assessing the loads from this cycle.”

Concepts for the Block 2 vehicle have evolved over the 10 years of the SLS program, but the BOLE upgrade could meet the performance requirement written into law by Congress beginning in 2010. 

“I’ll cautiously answer ‘yes,’ Reynolds said. “There’s always the possibility of more block upgrades on any part of the vehicle, so I say ‘cautiously’ because you never know what customer may come along that needs more capability that drives a compelling need for a block upgrade. But to answer your question succinctly, the EUS plus the BOLE integrated onto the block vehicle that we are currently on gives you that two-step process of the Block 1B and BOLE enables you to go to Block 2 and that is the capability that we’ve been asked to provide from the get-go on SLS.”

Quelle: NS

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Update: 17.07.2021

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Upper stage added to SLS stack in Vehicle Assembly Building

The upper stage for the first flight of NASA’s Space Launch System was installed on top of the heavy-lift rocket earlier this month, moving the agency one step closer to liftoff of the Artemis 1 test mission to the moon.

Teams inside the Vehicle Assembly Building at NASA’s Kennedy Space Center lifted the Interim Cryogenic Propulsion Stage on top of the SLS rocket stack July 5. The addition of the upper stage completed stacking of the propulsive elements for the first SLS mission, known as Artemis 1.

Last month, ground crews mounted the SLS core stage between the rocket’s two side-mounted solid-fueled boosters, which were stacked on a mobile launch platform inside the VAB earlier this year. Then teams added the Launch Vehicle Stage Adapter, a conical structure that tapes from the larger diameter of the core stage to the smaller upper stage.

The Interim Cryogenic Propulsion Stage, or ICPS, was built by United Launch Alliance and is based on the upper stage used on the company’s Delta 4-Heavy rocket. The ICPS will provide the boost to send NASA’s Orion crew capsule out of Earth orbit toward the moon on the Artemis 1 test flight.

No astronauts will fly on the Artemis 1 mission, but the test flight will pave the way for future piloted Artemis lunar missions, beginning with Artemis 2 scheduled for launch in 2023.

The five-meter-diameter ICPS contains liquid hydrogen and liquid oxygen propellant tanks to feed the stage’s Aerojet Rocketdyne RL10B-2 engine. The ICPS has a slightly larger liquid hydrogen tank than the Delta 4 upper stage, features a second hydrazine bottle for additional attitude control propellant, and has electrical and mechanical interfaces for attaching the Orion spacecraft, according to ULA.

Before transporting the upper stage to the VAB, teams loaded hydrazine fuel into the ICPS to feed maneuvering jets used to point the rocket in space.

During the Artemis 1 launch, the solid rocket boosters will fire two minutes, doing most of the work to lift the Space Launch System off pad 39B at the Kennedy Space Center. The core stage’s four hydrogen-fueled RS-25 engines, leftovers from the space shuttle program, will burn more than eight minutes to place the rocket into space with a velocity just shy of that required to reach a stable orbit.

The ICPS main engine will fire two times on the Artemis 1 mission, first for a Perigee Raise Maneuver to place the Orion spacecraft into around Earth, followed by a Trans-Lunar Injection burn lasting nearly 20 minutes to send the capsule toward the moon, ULA said.

The upper stage will then deploy the Orion spacecraft, which has its own service module for course correction burns and maneuvers to enter and exit lunar orbit, then return to Earth for a splashdown in the Pacific Ocean. The ICPS will deploy more than 13 CubeSats to explore the moon, asteroids, and other destinations in deep space.

NASA has ordered three ICPS units from United Launch Alliance to power the first three Artemis missions to the moon. Boeing is developing a more powerful Exploration Upper Stage with four RL10 engines for later Artemis launches.

The stacking of the SLS upper stage sets the stage for lifting of the Orion Stage Adapter, the attachment ring connecting the rocket with the Orion spacecraft.

Then a structure will go on top of the rocket to simulate the weight of the Orion capsule. The mass simulator will be atop the Space Launch System for testing to verify the propellant lines, fluid connections, and other umbilicals running between the mobile launch platform’s tower and the rocket can safely release and retract as they will at liftoff.

Then teams will move into structural resonance testing, or modal testing, of the fully-stacked launch vehicle. Once that is complete, teams will move the real Orion spacecraft — which will already be integrated with its launch abort system — to the VAB for attachment to the top of the Space Launch System, an event that sources say is now expected no sooner than September.

NASA will roll the fully-assembled 322-foot-tall (98-meter) Space Launch System from the VAB to pad 39B for a wet dress rehearsal this fall. The rehearsal is essentially a practice countdown, during which the launch team will load cryogenic propellants into the Space Launch System.

After the practice countdown, the SLS and Orion spacecraft will return to the Vehicle Assembly Building for final closeouts, inspections, and ordnance connections.

NASA Administrator Bill Nelson said Wednesday that the agency is holding to a target launch date for the Artemis 1 mission before the end of this year.

Quelle: SN

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Update: 13.08.2021

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Watch NASA fire up its SLS rocket engines to test far-out mission technologies

While NASA has yet to launch an Artemis mission to the moon, the agency is already doing engine testing for far-future missions.

NASA finished its sixth RS-25 engine hot-fire test on Thursday (Aug. 5), demonstrating advanced capabilities of an engine type that was used for decades during the space shuttle program that ran from 1981 to 2011. 

Engineers fired the  RS-25 engine, made by the California-based aerospace company Aerojet Rocketdyne, at NASA's Stennis Space Center in Mississippi for 500 seconds (more than eight minutes) to duplicate the time it will take four engines to boost the first stage of the massive Space Launch System (SLS) aloft.

"NASA already has tested engines for the rocket's first four Artemis missions to the moon, allowing operators to turn their focus towards collecting data to demonstrate and verify various engine capabilities for future engines," NASA said in a statement, adding the test allowed the team to look at new engine components to save cost, reduce operational risk and "enhance engine production."

The RS-25 test on Thursday also aimed to see how well new manufacturing processes are doing in terms of getting the engines ready for flight, NASA said. 

"NASA verified new manufacturing processes while evaluating the performance of the engine's low-pressure fuel turbopump," the agency said in the same statement. "The pump significantly boosts the pressure of liquid hydrogen delivered to the high-pressure fuel turbopump to help prevent cavitating, the forming of 'bubbles' or 'voids', which can collapse or cause shock waves that may damage machinery."

The uncrewed Artemis 1 mission aboard an SLS — marking the rocket's first space journey — is slated for a round-the-moon trip by the end of 2021. The crewed Artemis II moon-orbiting and Artemis 3 moon-landing missions are planned later in the decade, but when, the Biden administration has not yet confirmed. (NASA previously had set 2024 for the landing.)

Artemis represents NASA's efforts to establish a long-term presence on the moon and to open up exploration to more types of people than during the previous crewed effort in the 1960s and 1970s, called Apollo. 

The agency has pledged to put the first woman and the first person of color on the moon, following the 12 white men who landed on the surface between 1969 and 1972. International astronauts will also participate, unlike Apollo; an as-yet-unnamed Canadian astronaut is expected to join Artemis 2, for example.

Quelle: SC

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Update: 28.08.2021

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SLS cubesats arrive for Artemis 1 launch

 

COLORADO SPRINGS — While most of the cubesats manifested to launch as secondary payloads on the first Space Launch System mission have arrived, at least one of them will miss its flight.

NASA selected 13 cubesats several years ago to fly as secondary payloads on the Artemis 1 mission, launching no earlier than November. The cubesats, each six units in size, come from a mix of NASA, international and academic developers.

NASA released an image Aug. 11 showing the Orion stage adapter, the component that links the Orion spacecraft to the SLS second stage and which hosts the cubesats that will be deployed during the mission. The image shows nine cubesats installed on the adapter and the other four slots still unoccupied.

One of those four slots will be filled by BioSentinel, a NASA cubesat that will study the long-term effects of radiation in deep space on organisms, in this case yeast. That spacecraft has arrived at the Kennedy Space Center, NASA spokesperson Shannon Segovia said Aug. 19, but will be installed on the adapter last to preserve the biological samples onboard.

Two of the other three cubesats are part of NASA’s Cube Quest Challenge, a competition held by the agency’s Centennial Challenges prize program. NASA spokesperson Molly Porter said that one of them, CU-3E from the University of Colorado Boulder, is still expected to arrive in time for the Artemis 1 launch, but that the other, Cislunar Explorers from Cornell University, will not be ready for the flight. A third Cube Quest cubesat, Team Miles, has been installed on the stage adapter.

The other cubesat is Lunar Flashlight, being developed at NASA’s Jet Propulsion Laboratory to look for water ice deposits on the moon using lasers. That spacecraft is in danger of missing the Artemis 1 because of delays in the development of its propulsion system, JPL spokesperson Ian O’Neill said Aug. 20.

“Due to significant issues during testing of the originally procured Lunar Flashlight propulsion system, the mission switched to development of an alternative. This change occurred late in the project and delayed mission readiness,” NASA said in a statement about the cubesat. The pandemic then slowed development of the new propulsion system, which uses a “green” nontoxic propellant, by a group led by the Georgia Institute of Technology.

JPL has received the propulsion system, but O’Neill said it wasn’t clear that the system would be fully integrated and tested in time to launch on Artemis 1. “NASA is also exploring several near-term commercial launch opportunities for Lunar Flashlight in case it does not make Artemis 1,” the agency stated.

Exactly how much time CU-3E and Lunar Flashlight have to make Artemis 1 isn’t clear. Segovia said the cubesats must arrive in time to be installed on the Orion stage adapter before that adapter is installed on the SLS. NASA KSC spokesperson Tiffany Fairley said that installation is currently scheduled for early fall.

During a panel discussion at the AIAA Propulsion and Energy Forum Aug. 10, David Reynolds of NASA’s Marshall Space Flight Center said that the pandemic had caused some of the secondary payloads to fall behind schedule. “We’re trying to give them some opportunity to get caught up,” he said.

NASA is doing so by delaying the installation of the Orion stage adapter for as long as possible, using a mass simulator in its place for tests inside the Vehicle Assembly Building at KSC. “That will allow them to load in some of those secondary payloads for another month and a half,” he said.

Reynolds noted that the current planning date for the Artemis 1 launch is Nov. 26. “I wouldn’t book nonrefundable flights just yet,” he added.

Quelle: SN

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Update: 3.09.2021

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NASA’s hopes waning for SLS test flight this year

The earliest NASA’s first Space Launch System moon rocket could roll out from the Vehicle Assembly Building to its seaside launch complex in Florida is in late November, officials told Spaceflight Now, leaving little time to conduct a critical fueling test, roll the rocket back into the VAB for final closeouts, then return to the pad for liftoff before the end of the year.

Stacking and testing of the SLS heavy-lift rocket has taken longer than NASA’s best-case projections earlier this year. But that’s not unexpected for the first time teams have assembled the powerful new launch vehicle inside the VAB at NASA’s Kennedy Space Center.

“It’s gone well, in my opinion, for first-time operations,” said Cliff Lanham, senior vehicle operations manager for NASA’s exploration ground systems program, in a recent interview with Spaceflight Now. “Everything is new for us, but in general, things have gone well.”

Lanham said NASA, supported by ground systems contractor Jacobs, intentionally delayed stacking of some elements of the Space Launch System this summer to complete some “higher-priority” work in the critical path for the first unpiloted SLS test flight, which NASA calls Artemis 1.

The higher-priority tasks included an initial power up of the SLS core stage avionics, and loading of flight software into the rocket’s computer system. The work also involved checkouts of an environmental control system before power-up of the rocket.

NASA engineers have not discovered any major problems during the SLS testing, but key milestones leading up to the Artemis 1 launch have been steadily sliding to the right in NASA’s processing schedule.

Before NASA raised the Boeing-made SLS core stage onto its mobile launch platform inside High Bay 3 of the VAB in June, managers hoped to connect he Orion spacecraft for the Artemis 1 mission on top of the rocket in August. That’s now expected this fall.

The first rollout of the 322-foot-tall (98-meter) rocket from the VAB to launch pad 39B was scheduled no earlier than September. That’s now expected in late November, at the soonest, according to Lanham.

The schedule slips, while not significant amid the history of SLS program delays, have put a major crunch on NASA’s ambition to launch the Artemis 1 mission this year. The agency is evaluating Artemis 1 launch opportunities in the second half of December, multiple sources said, but that would require NASA to cut in half the time it originally allotted between the SLS fueling test and the actual launch date.

With opportunities eroding to launch the Artemis 1 mission before the end of the year, the SLS test flight is more likely to take off some time in the first half of 2022.

Earlier this month, NASA stacked a test article of the Orion Stage Adapter on top of the SLS in High Bay. The flight adapter will connect the Orion spacecraft with the SLS upper stage, and will also carry around a dozen CubeSats into deep space as rideshare payloads.

Then ground teams lifted a cylinder called the Mass Simulator for Orion on top of the rocket. That structure mimics the weight of the Lockheed Martin-built Orion spacecraft, allowing technicians to complete resonance measurements on the entire rocket stack, a milestone NASA calls modal testing.

With the mass simulator stacked, ground teams began a series of interface verification tests earlier this. Those will be followed by an Umbilical Release and Retract Test, in which engineers will verify the release system for the swing arms routing fluid and support connections between the mobile launch tower and the SLS rocket.

The swing arms will rotate or drop away from the rocket at liftoff.

Then teams will move into modal testing. Stingers, or shakers, will introduce vibrations to the rocket as it stands on its support posts at the base of the mobile launch platform. Sensors across the rocket and along the mobile launch tower, will measure the resonant response to the vibrations.

The rocket’s twin side-mounted solid-fueled boosters each stand on four vehicle support posts, with the vehicle’s weight holding it on the mobile platform — without the support of hold-down bolts — during stacking, rollout, and the countdown before liftoff.

Lanham said NASA’s ground systems team hopes to finish the modal testing in September.

So we would get into, you know, towards the end of August into early September timeframe, we would get into URL T followed by modal, and ideally finish up in the middle of September with modal testing.

That will be followed by removal of the Orion mass simulator and the Orion Stage Adapter test article. Those will be replaced by the flight-ready stage adapter and the real Orion spacecraft, which has been fueled with in-space maneuvering propellant and mated with its launch abort system at Kennedy.

Technicians are completing installation of ogive fairings over the top of the Orion spacecraft, providing the aerodynamic shield that will cover the capsule during launch.

After additional tests to verify the mechanical and electrical connections between the Orion spacecraft and the SLS rocket, NASA will be ready to roll the fully-assembled launcher to pad 39B atop one of the agency’s Apollo-era crawler transporters.

The rocket will spend about a week on the pad before NASA’s launch team runs through a simulated countdown, culminating in the loading of super-hold liquid hydrogen and liquid oxygen aboard the launch vehicle.

Assuming that test, known as a wet dress rehearsal, is a success, teams will drain the propellant, safe the rocket, and return the Space Launch System to the Vehicle Assembly Building for final closeouts.

The time-sensitive work inside the VAB after the wet dress rehearsal will include the installation of pyrotechnic ordnance for the rocket’s separation systems and range safety destruct mechanism, which would terminate the flight if the rocket flew off course after liftoff.

Then the rocket will roll back out to pad 39B for another week of preparations ahead of the first launch attempt.

During launch, the core stage’s Aerojet Rocketdyne RS-25 engines and twin solid rocket boosters will generate 8.8 million pounds of thrust. It can send about 59,500 pounds (27 metric tons) of payload to the moon, according to NASA.

The Artemis 1 mission will propel the Orion spacecraft on a mission to orbit the moon for several weeks, before the capsule returns to Earth for a splashdown in the Pacific Ocean. Artemis 1 will pave the way for the next SLS/Orion mission, Artemis 2, to carry a four-person crew around the moon in 2023.

Artemis missions later in the 2020s will land astronauts near the south pole of the moon using commercially-developed lunar landers. In April, NASA selected a variant of SpaceX’s Starship, a reusable heavy-lift rocket being developed with majority private funding, to land the first Artemis crew on the moon.

But NASA plans to use the government-owned Space Launch System rocket and Orion capsule for the round-trip flight between Earth and the vicinity of the moon, where astronauts will transfer into a lunar lander, such as the Starship, for descent to the surface.

Quelle: SN