Spaceflight Insider

NASA discusses SLS and Orion progress at ‘Day of Mars’ event

Artist's concept of Orion docked with a nuclear thermal engined Mars Transfer Vehicle.

An artist’s concept of Orion docked with a nuclear thermal-engined Mars Transfer Vehicle. Image Credit: NASA

NEW ORLEANS — Before wowing onlookers with the sights and sounds related to testing an RS-25 engine, NASA sought to educate members of traditional and social media outlets about agency and industry efforts related to the Journey to Mars.

However, before the agency can begin sending ships and crew beyond Earth’s neighborhood, they must first complete the rocket and spacecraft that will enable that journey. A televised panel discussion with NASA personnel started the day with a status update of the Space Launch System (SLS), accompanied by a discussion of the challenges the agency must consider in reaching the Red Planet with a crewed mission and the efforts underway to overcome them.

Structural test article for the Orion crew access tunnel on display at Michoud.

The structural test article for the Orion crew access tunnel on display at Michoud. Photo Credit: Curt Godwin / SpaceFlight Insider

Bill Hill, NASA’s deputy associate administrator for Exploration Systems Development, outlined the progress the agency is making with SLS.

Exploration Mission 1 (EM-1), the maiden launch of the SLS, is still on-track for a late 2018 liftoff and will send the Orion spacecraft on a distant retrograde orbit around the Moon. It will be the only mission to use the Interim Cryogenic Propulsion Stage (ICPS). The pressure vessel for that Orion craft has already been delivered to Kennedy Space Center (KSC) in Florida.

“I would have preferred for [the mission] to have been called EFT-2,” Hill said, in an apparent nod to the experimental nature of Orion’s previous mission on Exploration Flight Test 1 (EFT-1).

Notably, though not related, Hill also mentioned it is NASA’s ultimate goal to turn over the International Space Station to commercial entities at the end of the agency’s commitment in the mid-2020s.

Lara Kearney was also on-hand to explain some of the changes in the Orion spacecraft following its maiden flight in December 2014 atop a Delta IV Heavy.

Kearney, NASA’s Orion Crew and Service Modules manager, noted the spacecraft has evolved from 31 separate structural pieces for the EFT-1 mission to seven for the EM-1 flight. Not only has the number of structural components been significantly reduced, but nearly 1,000 pounds (453 kilograms) of mass has been removed from the spacecraft.

Prior to visiting the Vertical Assembly Center, where the world’s largest spacecraft welding tool is nearing completion of the flight article for the mammoth liquid hydrogen tank for the SLS core stage, SLS Stages Element Manager Steve Doering allowed for a small detour to see the completed structural test article for the tank.

NASA's Steve Doering discusses the process of making the SLS core stage liquid hydrogen tank.

NASA’s Steve Doering discusses the process of making the SLS core stage liquid hydrogen tank. Photo Credit: Curt Godwin / SpaceFlight Insider

Currently undergoing installation of sensors, the 130+ feet (∼40 meters) long tank will eventually be shipped to NASA’s Marshall Space Flight Center (MSFC) in Huntsville, AL, where it will be subjected to simulated flight loads in a recently-constructed test stand so that the design can be validated.

Beyond simply discussing the progress of SLS and Orion toward EM-1, NASA also provided access to propulsion experts.

To date, all human-rated spacecraft have relied on chemical propulsion, whether it be solid fuel, cryogenic, semi-cryogenic, or hypergolic. However, there is a theoretical limit to the efficiency one can expect out of those more traditional methods: approximately 450 seconds of specific impulse (Isp). Isp measures the change in momentum delivered per unit of propellant consumed by the engine. One can roughly equate this to the fuel economy rating of an automobile.

Due to the inherently more efficient nature of a nuclear thermal rocket engine – originally tested more than fifty years ago as part of the NERVA (Nuclear Engine for Rocket Vehicle Application) program – there is renewed interest in the practical use of the technology for deep space missions. The NERVA tests showed an efficiency level of 850 seconds Isp – nearly twice that of the RS-25.

Tony Kim, project manager for nuclear propulsion at NASA’s Marshall Space Flight Center, is in the early conceptual design phase for a restart of the program and is confident that efficiencies can be increased to 1,000 seconds Isp.

Kim, an emphatic supporter of nuclear thermal engines, posits that such an engine would be safe to launch and would be much safer for astronauts as it would reduce total flight time on a Mars mission by 3 to 4 months, directly reducing the amount of time the crew would be exposed to potentially harmful radiation, both from the sun and from interstellar sources. Such an engine would only use 5.5 pounds (2.5 kilograms) of low-enriched uranium on a round-trip mission to the Red Planet, in addition to its liquid hydrogen propellant.

Though nominally a topic of public derision, Kim asserts now is the time to resume work on a nuclear thermal engine and he feels the public is ready.

“We understand nuclear power,” Kim said when asked about his rationale.


Curt Godwin has been a fan of space exploration for as long as he can remember, keeping his eyes to the skies from an early age. Initially majoring in Nuclear Engineering, Curt later decided that computers would be a more interesting - and safer - career field. He's worked in education technology for more than 20 years, and has been published in industry and peer journals, and is a respected authority on wireless network engineering. Throughout this period of his life, he maintained his love for all things space and has written about his experiences at a variety of NASA events, both on his personal blog and as a freelance media representative.

Reader Comments

Franklin Miller

I recently revisited the U boat at the Chicago museum. The submarine veterans might be a good source of advice and experience on long duration isolated confined missions.

True, but of course they remained on Earth the entire time. If something went really wrong, they had the option to surface and be rescued within hours at most. A mission halfway to Mars will not be so fortunate. But I know, fortune favors the bold. Let’s just hope they remain mentally intact once they get there. I have read more than enough about arctic and antarctic explorers who tried to John Wayne there way through enduring the isolation, cold, etc. and ended up dying at their own hands, not the elements. And again, this is on Earth.

I’m really happy to see that there is interest and efforts ongoing to make nuclear thermal engines feasible. We cannot and should not rely on eletric propulsion. This is not what we need. Let it for the robotic exploration. Crewed missions need faster propulsion to avoid the issues related to the radiation.

My main concern with focusing on nuclear power for manned deep space missions is that their development will cause even further delays to NASA’s manned Mars plans, which are already well into the 2030s. Plus there are still plenty of folks who have issues with anything nuclear in general, even when used for peaceful space exploration. Just ask Cassini.

Yeah, it would cause delays for the manned missions, but I think its a step we should take. There is no need to hurry when the outcome overcomes the time spent. I dont remember where but i once read that the way plutonium is enriched and prepared make it useless for weapons, so if it’s true, people should be educated and nuclear power should be demystified.

We are in agreement. The reason I am suggesting we do things sooner rather than later are not technical issues but political ones.

There is no guarantee that some President down the road won’t show even less interest in space than most of them usually have and kill the manned Mars project. Look what Obama did to the Constellation program for a proposed lunar colony in the 2020s:

Reviving the NERVA program is a no-brainer, but the application should be for deep space missions, and not the Mars program. It would become just another stumbling block slowing down the already lagging NASA manned mission. The Mars program has already had too many “but first we must…” NASA should shell over some cash to SpaceX and be supportive of their drive and determination to get us moving in an outward direction again. NASA simply has too many divergent and effort-diluting projects. We also need to build a transportable nuclear reactor for powering the propellant production based on Mars’ surface. We need a 100KW transportable to do the job, and that’s a small reactor. Similar reactors could be incorporated into future deep space probes to power instrumentation as well as increasing data return through higher signal strengths and data return rates facilitated by transmitter power. I know there are many anti-nuclear activists, but they simply need to “get over it.” If they don’t want to use weapons grade isotopes, use a Thorium-based system.

Rodger Raubach

Just a few words clarifying my deep space mission comment above; that refers to missions beyond the orbit of Mars, including the asteroids as well as gas giant planets. Chemical propulsion is adequate for travel to the Moon and Mars.

Actually, it might very well be quite the opposite. Since beyond Mars, water is even more accessible at shallow gravity wells, on-site refueling is a no-brainer and the tankage is *vastly* smaller for the same delta V capability on the vehicle.

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