Garry Lyles is Chief Engineer for the Space Launch System Program office at NASA’s Marshall Space Flight Center. In 2012, the National Space Club named Lyles the Astronautics Engineer of the Year in honor of his decades of advancing the nation’s human spaceflight systems.

NASA Tech Briefs: What is the Space Launch System?

Garry Lyles: It’s the heavy launch system that is designed to take humans and cargo beyond lower Earth orbit. It is the next big capability with the Orion MPCV (Multi-Purpose Crew Vehicle). The Space Launch System is being designed as an evolvable technology. It’s starting out with capability of [carrying] 70 metric tons to lower Earth orbit, which is kind of a reference point for us. It is a drop-off point that allows us to design against a certain set of requirements. Then we have an evolved capability to greater than 100 metric tons, and then greater than 130 metric tons for the future long-term missions and missions that require capability that we’ve really never had before: the capability to send humans to Mars.

NTB: What kinds of missions will this Space Launch System enable?

Lyles: We’re very flexible, so we can take care of missions like the one we’ve announced recently to rendezvous with an asteroid. We can do any cis-lunar space mission. In the evolved cases, we could actually go rendezvous with an asteroid in its own orbit. We can do robotic missions with this launch vehicle that would allow science missions to make a much faster trip to the outer planets. We can eventually take humans to Mars.

NTB: And what else can this potentially carry to deep space?

Lyles: Block 1 (70 metric tons) is being designed to carry the MPCV Orion and its crew. We have capability being designed for future missions, which would include just carrying cargo or robotic spacecraft. But remember: SLS is being designed as a capability. It’s a national capability that could carry anything outside the capability of current systems, or systems that need additional capabilities for planetary missions and solar-system missions.

NTB: Is this the best system yet technologically?

Lyles: I would say yes, and the reason I say that is because we have been evolving our capability in launch systems for quite awhile now. We have evolved from the Saturn kind of [rocket]systems, through the shuttle program, and shuttle actually gave us a lot of technological advancements. What we’ve done is take those technological advancements as a first capability for SLS and integrated those into a vehicle that is much more capable than shuttle was to go beyond lower-Earth orbit. Then we have the capability with this vehicle to employ future technologies for things like advanced boosters and advanced upper stages that we can integrate with this vehicle, and it will continue to evolve as the technology evolves.

NTB: What are the challenges of building a 321-ft, 5.5-million pound rocket?

Lyles: It is long. With most launch vehicles, the biggest challenge we've had is to integrate heritage systems, or legacy hardware, into an integrated vehicle that works together. And size is one of those challenges. We went through quite a concept analysis phase with this vehicle, and it was determined, based on a lot of analysis, that the most effective way for us to reach a capability for beyond lower-Earth orbit was to utilize a lot of the capability that was developed in-shuttle and capability that was being developed as part of the Constellation and Ares spaceflight program.

From a cost-effective and schedule-effective design, we determined that we could afford to develop one major subsystem of a rocket of this size. We chose that subsystem to be the core stage. Our core stage is a new design, but we were able to utilize existing rocket engines from the shuttle program, the RS-25s, our space shuttle main engines. We had 16 of those engines available to us to utilize for this launch vehicle, which means we didn’t have to start from scratch and develop a rocket engine, which is usually the most difficult part of a rocket’s development. We also had the space shuttle boosters, which had been in an evolution process as part of the Ares project and Constellation, to evolve that booster to a five-segment booster. We were able to utilize that design, which has now had three full-scale development tests, and we’re heading very rapidly towards its first qualification test.

When we looked for an upper stage, to do the in-space part of the mission, we found that we could do a significant number of missions in cis-lunar space with the current Delta IV upper stage, which we are calling the Interim Cryogenic Propulsion Stage, or ICPS. We were able to take existing systems —the boosters, the engines, the ICPS (Interim Cryogenic Propulsion Stage)— and integrate them with a new core stage, which is the backbone of the rocket. It allowed us to move forward very rapidly toward a 2017 launch, at what we believe is a minimum cost for a rocket of this size.

That being the case, it brings us to the job of integrating all that hardware, which was designed for a different purpose and a different system, into a system that will operate together. This vehicle doesn’t fly exactly like a Delta, so the loads on the ICPS are different. The vehicle doesn’t fly like Ares was going to fly, so the loads on the boosters are a little different, and the environments for the space shuttle main engines, the RS25s, are different on this vehicle; we’ve relocated them under the core stage. We’ve had to go through a very iterative process in integrating this vehicle so that it works together, to make sure we don’t have to go back and re-design hardware that is already designed; that would be a very expensive thing to do. The greatest challenge is the integration of heritage hardware into a working vehicle design, while keeping on schedule and budget.

NTB: What is being done with SLS currently? Is it in the design phase? Testing phase?

Lyles: Today we are in the Preliminary Design review and are getting really close to setting the design of this vehicle to the way it will fly and operate. This is a critical part of the design, and at this stage, we have a lot of confidence in this rocket. We do have some challenges going forward, but we have mitigation plans with multiple solutions. The design phase of the core stage is very rapidly approaching critical design review next year, and they are essentially designed. Once that is set as the primary structure, we have very little that we would want to change in primary structure from a vehicle integration point of view.

As for testing, we have done and are planning for several tests in wind tunnels. We started with the 14” tunnel at MSFC, and have moved on to bigger ones, like the one at Langley, to complete transonic tests and booster separation tests. In mid-August we are working towards our fourth big test – the aero-acoustics of the vehicle at Ames Center. These wind tunnel tests are large 11-ft tunnels, using 2.5% to 3% full-scale vehicle models with lots of pressures and aero environments. We are also moving rapidly to a scaled test here at the center to demonstrate acoustics on the pad; this will use a sub-scale rocket with model RS-25 engines.

At this point, we are essentially looking at the environments – acoustics, ignition over pressure, assent acoustic loads, buffet, gust winds, and atmospheric winds. This is all a good set of data that we are working with within any envelope of potential environments that we may encounter.

NTB: Why is SLS so important?

Lyles: SLS is a national asset with an unprecedented mass capability to take humans and payload outside of low earth orbit. The long-term strategy for SLS’s evolvability gives us the capability to get to our end goals – sending humans to cis-lunar space. Mars has long been the focus of future exploration. There are many other places within our reach right now and those missions require a capability to lift heavy payloads. The single thing that differentiates us from [the] Saturn [moon rocket] is our ability to carry large volumes: science payloads, experiments, and habitats. The cargo capability with a 10-meter diameter fairing is significant. The propulsion muscle we have coupled with the large payload capability is unique to SLS and any future beyond low earth orbit.

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