Spaceflight Insider

NASA’s SLS Program Manager talks Block 1B and beyond – Part Three

NASA Space Launch System Block 1 NASA image posted on SpaceFlight Insider

SpaceFlight Insider's exclusive interview with NASA"s Space Launch System Program Manager Todd May concludes with this third installment. In it, May details efforts to use SLS to carry out missions to the outer Solar System as well as the differences between the Block I and II versions of the booster. Image Credit: SLS

SpaceFlight Insider brings you the next segment of our exclusive interview with NASA’s Space Launch System (SLS) Program Manager Todd May. In this segment, May discusses how the new rocket can be used to carry out missions to the outer Solar System, the differences between the Block 1 and Block 2 – and much more.

SpaceFlight Insider: Can you provide our readers with an example of how SLS could improve deep space exploration efforts?

May: “A good example can be found with New Horizons – that spacecraft only weighed 950 lbs. If you look at a cutaway of the spacecraft atop its Atlas V 551, it looks like a little angel dancing on the head of a pin – it’s a tiny little thing up there.

“Now imagine that you wanted to get there fast [it took New Horizons nine years to get to Pluto] and if you were to throw a stage on there, so that the spacecraft was actually able to slow down, it would be able to go into orbit around Pluto – instead of just getting 48 hours worth of science.

A Block 1 Space Launch System booster takes off from Launch Complex 39A  at Kennedy Space Center in Florida image credit NASA posted on SpaceFlight Insider

NASA hopes to launch the first flight of SLS in 2018. Image Credit: NASA

“SLS opens up the outer Solar System in a manner that the scientists are starting to get now. Voyager [1] passed the heliopause a year or so ago. That took over thirty years to get there. We’ve estimated that SLS could get an interplanetary probe to the heliopause in 10 years.

“So, the further you go out, the more the trade is in terms of direct insertion and if you’re a scientist – imagine that you’re a 60-year-old scientist and this thing launches. Think about it, 30 years from now, you can pretty much bet that you have a less than even chance of even being alive when the science comes back. If it’s just ten years? That increases the likelihood that you are going to be able to get it. So, SLS does kind of change the game for these principal investigators out there.”

SpaceFlight Insider: So, from what we’ve just heard you say, it sounds like using SLS for the Europa mission is still in the offing. Is that correct?

May: “I think we have captured the excitement of the science community – I’ll say that much. Any kind of mission like this is going to be what we would call a flagship mission.

“To create the funding wedge for a mission like that is something that does not happen overnight. It is something that the community has to advocate and ultimately it gets written into law. But, I will tell you that the Europa mission, for the last several years now, has gotten steady funding. So I think that it has gotten serious advocacy now in the scientific community, and I think certain members of Congress are very interested in this mission.

“To be fair, these missions are achieved by appropriated funding and there’s a process that it goes through.

“I think some of what we’re seeing is that the capabilities of the rocket is starting to speak for itself now. They’re coming to us. So, the Europa guys, Tom Gavin, when he was the pre-project manager, and Barry Goldstein, who’s the project manager now, they came to us and they asked, ‘Can you guys do a direct insertion? – We don’t like having to do the flybys and taking seven years to get out there.’

“We can also save operations costs by not having the team waiting for seven years before we get there. So, we showed them the trajectories and, sure enough, we’re showing under two-and-a-half years – even at a full five metric tons.”

Space Launch System 70 mt 130 mt metric ton NASA image posted on SpaceFlight Insider

May detailed how SLS will progress from the Block I to the Block II version. (Click to enlarge) Image Credit: NASA

SpaceFlight Insider: You mentioned how members of the scientific community came to you for the Europa mission. We’ve also noted that the folks over at Inspiration Mars, Dennis Tito, and Taber MacCallum, they also came to you to use SLS and Orion to conduct a crewed flyby of Mars… 

May: “They actually flew down here, and we had dinner and they convinced us that we could uniquely give them what they were after. We were authorized to engage in discussions with them and provide them with all of the data that they needed to put their story together. That type of mission has to have the same kind of support. There’s a lot of advocacy that has to happen to pull that type of mission off. But, I think again, that someone like Dennis Tito – who is as big a commercial spaceflight fan as anybody because he is the first tourist ever in space –  he came to us and said, ‘We think your rocket is the solution to what we are trying to do.’”

Video courtesy of NASA’s Jet Propulsion Laboratory

SpaceFlight Insider: The commercial space community has not always sung NASA’s praises, do you think the fact that key members of that group come to you  do you think that shows the need for SLS?

May: “There are different types of commercial spaceflight people. There are people who are selling a rocket, or a launch capability, who would view us competitively, and then there are people who have payloads that they want to get somewhere, like a Dennis Tito. Those types of people are coming to us.

“I’ll give you another one – Bigelow. [Robert] Bigelow came to us two years ago and said, look, I can take an Atlas V 551 and launch my 3100 into space empty – but then I got to conduct another launch to place the stuff in there and then another launch to put the water up there. He asked us, ‘Can you launch a fully outfitted 3100?’ And the answer is yes, and he says, ‘I’ve also got this idea for one called a 4500, and it’s twice the volume of the International Space Station and it’s designed to have 16 astronauts, here’s the dimensions and here’s the mass – can you launch this?’ And the answer is yes.

“Here’s what really blows me away, if you look at how many launches it took to put the International Space Station, with shuttles and Soyuz and Progress – it was over 25 shuttle launches, a whole bunch of Soyuz launches and a lot of Progress launches – and you get this idea that you could launch a space station with twice as much volume as the ISS in just one launch; that speaks for itself as well.

“I think that this community sees that. I had a conversation with Firouz Naderi from JPL, and he and his guys, John Baker and Hoppy Price, they presented a paper at the ‘Humans to Mars’ summit that had an entire architecture built around SLS and Orion and were – these are JPL guys – they were making the case that it’s an affordable scenario. Now, I can’t tell you that this is an official NASA policy or anything like that. My point is that JPL is a science center, and they are so excited about it that they went out and put together a presentation that showed that this works.

Martian moons Phobos and Deimos NASA APOD image posted on SpaceFlight Insider

May detailed how he is excited by the potential prospect of sending astronauts to the Martian moons Phobos and Deimos using SLS. (Click to enlarge) Image Credit: NASA

“They got really excited about Phobos and Deimos [the moons of Mars] and I kind of like that too because you can get humans to Phobos or Deimos – which is, essentially, at Mars without having to do the full-up lander, which it is pretty hard to land things on the surface because there’s an atmosphere. But, with about half of the Delta V, you can [go] to Phobos and Deimos and just kind of dock up next to them and so it’s easier to get there and I’ve always been a fan of humans at Phobos and Deimos first. When you have an astronaut standing on Phobos with Mars looming in the background, it’s huge, just over the astronauts head; I think the rest of the program sells itself.

SpaceFlight Insider: We’ve all seen the trailers for Andy Weir’s book, “The Martian”, and they show a spacecraft that is large, larger than the International Space Station. From what we understand, that is what we currently believe will be required for an actual mission to Mars. How many launches do you think a crewed mission to Mars would require?

May: “That’s a hard one for me to answer, because I’m somewhat afraid that I’m going to let your readers down here as I tend to focus on the rocket; I will say that I have spoken with Firouz and I’ll just tell you what I saw in their package and that is that you can get humans to Phobos, Deimos, and back for four launches of SLS. I think that they had six launches if you wanted to get to the surface.

“But, Tito, if you want to just go by Mars and wave at it, you know, his deal is you can do it in just one, or maybe one plus the launch of it and the crew capsule or something like that. Initially, he was thinking that with the Block IB, you would have the hab [habitat] behind it, you could have the family, you know, the husband and wife team go around the backside of Mars and take pictures.

NASA Space Launch System SLS booster Orion spacecraft infographic NASA image posted on SpaceFlight Insider

Image Credit: NASA

“So, in the end, the answer is – it depends. It depends on how sparse that you want to be, as you know there are some people who are considering a one-way trip; that, of course, means less flights. If you want to bring them home safely, I think that four-to-six is a reasonable number.”

SpaceFlight Insider: So, might we be able to see earlier versions of SLS carry out missions suited to their specific capabilities – or will they be phased our in favor of newer versions as they are made available?

May: “Let me explain Block IB and Block II so that your readers can get an idea of the differences between Block I and Block II. There is really only two major things that you’re doing between Block I and Block II; the first, to go from Block I to Block IB, you add to the upper stage and Block IB has both crewed and fairing versions, and then there are 5, 8, and 10 meter versions of that fairing. Now Block II has the advanced boosters, and those are the ones that we have been saying for some time now could be advanced solids or liquids. That’s it. Those two developments get you to the 130 metric ton, to as much [as] a 150 metric tons to LEO [low-Earth orbit], which is, for all practical purposes, Mars capable.”

SpaceFlight Insider: Todd, we know that you’ve got a busy schedule today and we don’t want to take up any more of your time. Thank you so much for chatting with us today.

May: “No problem at all, there’s a lot of exciting things going on these days and we’re happy to share them with your readers.”



Jason Rhian spent several years honing his skills with internships at NASA, the National Space Society and other organizations. He has provided content for outlets such as: Aviation Week & Space Technology,, The Mars Society and Universe Today.

Reader Comments

Great interview, Jason – thanks for posting this. My wife Karen and I had the pleasure of meeting Todd May last March at the QM-1 test. Todd is a great evangelist for NASA and for human space flight.

Matt McClanahan

“Bigelow came to us two years ago and said, look, I can take an Atlas V 551 and launch my 3100 into space empty – but then I got to conduct another launch to place the stuff in there and then another launch to put the water up there. He asked us, ‘Can you launch a fully outfitted 3100?’ And the answer is yes”

And that’s why I have difficulty taking discussions of ISS operating beyond 2024 seriously. It’s a station whose modules are built almost entirely within the Shuttle cargo bay form factor, which is no longer a relevant constraint. The numbers for keeping ISS flying vs launching a modern, spacious station, just don’t add up, IMHO.

Robert Gowitt

This three part series has been interesting from the word go. I’ve learned a nuber of things I knew nothing about. Seeing the goals laid out by Todd May clarifies the what and why of SLS. Excellent work!

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