We spoke to the chief engineer on NASA’s new heavy-lift rocket about how development is progressing
What is your role as chief engineer?
My job is to manage the design of SLS from a technical point of view, so day-to-day I make decisions on any design changes that need to be made to the launch vehicle. At the end of July we’ll hold a review board and basically make a decision as to whether we’re ready to proceed on to Critical Design Review in about 18 months or so.
Is everything on track for the first scheduled flight in December 2017?
Yes, as a matter of fact we do still hold a little schedule margin, and we expect to fly towards the end of 2017. There’s nothing right now in the design or what we’ve seen in the reviews that’s [been a problem]. Everything is on track, and the design is falling together really well so far.
What are the major difficulties in building a rocket of this size?
Most rocket designers would probably tell you the biggest problem is propulsion, as the most complex part of a rocket in general are the engines and boosters. In our case, since we have heritage engines and boosters, the most complicated part is integrating those parts together to make a vehicle that will fly.
Why are heavy-lift rockets so important?
The further away [from Earth] you want to go, the bigger the rocket has to be. That’s primarily because you have to carry large amounts of propellant for the portion of the mission in space. One mission we’re looking at now is capturing an asteroid and bringing it back to lunar orbit. The Moon is 1,000 times further than the ISS, so it takes quite a bit of additional propellant to get there. And if we want to go even further, to rendezvous with an asteroid or go to Mars, for example, you need a lot of propellant. The more propellant you need, the bigger the launch vehicle has to be.
Is SLS imperative for manned deep space missions?
Since SLS is human rated, one of its primary missions is human spaceflight beyond LEO. Humans are needy things; they require lots of room, environmental control, radiation protection, water and all these things. So crewed missions need [a lot of cargo] and, plus, you want to get them [to their destination] as quickly as possible. To get them there quickly you need a large stage and you will carry a lot of propellant with you to burn and get the crew there as fast as you can.
How long will the SLS be in service?
As long as we need it to be. The one thing that we have planned into this vehicle is an evolution of capability. So, while in 2017 we’ll fly a vehicle [Orion] with 70 tons of payload capability, we have multiple options that can evolve that vehicle into 105 tons, and finally to greater than 130 tons.
Is this the biggest rocket currently needed?
I think with the capability that we have the Space Launch System is the biggest rocket that you would want to build. Eventually, though, we have plans that go well beyond 130 tons. Things like liquid boosters, which would provide some of the same kind of capability that the Saturn V had except strapped on to the side of the SLS, may provide as much as 150 tons of capability. I think it will be what we need for a very long time.