Human flight around the Moon: a worthy goal, but using the wrong vehicles
by Gerald Black
|Restarting beyond Earth orbit missions with so much less flight testing than our predecessors dared do on the Apollo program makes me hesitate.|
The idea of moving boldly and swiftly forward with beyond Earth orbit human missions has a lot of merit. We been going in circles (literally) for too long, stuck in low Earth orbit (LEO). Missions beyond LEO would inspire young people to pursue careers in math and science, the same way that the Apollo missions did in the 1960s and 1970s.
But the proposed plan has drawbacks. It would delay, and add to the cost of, EM-1. The second stage of the SLS, the Interim Cryogenic Propulsion Stage (ICPS) would have to be human rated, which would add about $150,000,000 to the cost of the EM-1 mission. NASA had planned to avoid this expense by flying the ICPS only once, then switch to the more powerful human rated Exploration Upper Stage (EUS) for EM-2 and subsequent missions. Other items, including a life support system and an active launch abort system, would also need to be added. A flight test of the launch abort system would also need to be conducted prior to EM-1. These are all things that are not currently planned for the EM-1 mission.
The most serious drawback to the proposed plan, however, is the added risk to the first crew. Flying crew on the first flight of a new launch vehicle is not without precedent. The first flight of the Space Shuttle had a crew. However, the shuttle only orbited the Earth and could quickly return if a problem developed. The Orion capsule, however, would embark on an flight around the Moon lasting more than a week. If a problem occurred at the wrong time, it would take days to get back to Earth.
And it’s not just that it is the first flight of the SLS. The Orion capsule has not been adequately flight-tested, either. The Orion capsule did make a single, short uncrewed flight in December 2014, when a Delta IV Heavy rocket boosted the capsule to a high Earth orbit for a five-hour mission. This flight was successful, but the life support system was not installed and the capsule only attained a velocity about 80% of that of a return from the Moon—not enough to fully test the heat shield. Not only that, but this flight lacked the service module that is the critical second component of the Orion spacecraft. The service module, which will be supplied by the European Space Agency, has never been flown and there are no plans to do so prior to the EM-1 mission.
The most bold and ambitious human spaceflight program to date was the Apollo program, so it’s instructive to look at how much flight testing was done on the Apollo program before the first crewed lunar flight. The Saturn V and the Apollo command and service modules were all tested twice uncrewed (Apollo 4 and Apollo 6) before the first crewed flights. On the Apollo 6 flight, a severe pogo oscillation occurred, damaging some of the engines in the second and third stages of the Saturn V, rupturing internal fuel lines and causing two second stage engines to shut down early. Thankfully this problem was fixed before the first crewed flight of the Saturn V (Apollo 8, which orbited the moon in December of 1968). The Apollo command and service modules were also tested with a crew aboard on an 11-day mission in low earth orbit (Apollo 7), prior to the first Apollo lunar flight.
|My own belief is that we should go with the commercial alternatives to SLS and Orion. The commercial alternatives are more innovative and employ newer technology than the government solution.|
I do think that NASA has been too risk-averse in its human spaceflight endeavors. It is also true that spaceflight experience, extensive ground testing, and modern computer analysis methods have lessened the need for flight testing. Yet, unanticipated problems like the Saturn V pogo oscillations still do occur, especially on the inaugural flight of new launch vehicles. And many problems with the life support system on the International Space Station were encountered under zero-g conditions that failed to show up during ground testing. Restarting beyond Earth orbit missions with so much less flight testing than our predecessors dared do on the Apollo program makes me hesitate.
Hmm. It’s too bad that this bold plan to swiftly restart human spaceflight beyond Earth orbit incurs a higher-than-desired risk to the precious lives of our astronauts. But wait: there is a better way. The same objective of an early human flight around the Moon could be accomplished with much lower risk by switching instead to SpaceX’s Falcon Heavy launch vehicle and Dragon 2 (also known as Crew Dragon) capsule. This can be done with very little modification to the hardware, since SpaceX from the beginning designed the Falcon Heavy to be human rated and the Dragon heat shield to be capable of lunar return.
As per Friday’s media teleconference, NASA will constrain its study of crewed EM-1 missions to those that can be performed by the end of 2019. But by the end of 2019 SpaceX will likely have performed somewhere between three and five crewed flights of the Dragon 2 to the ISS and at least three flights of the Falcon Heavy. Furthermore, there is sufficient time to conduct an uncrewed flight of the Falcon Heavy/Dragon 2 around the Moon prior to the crewed flight, all by the end of 2019. This flight experience is what would make the Falcon Heavy/Dragon 2 much safer than the SLS/Orion.
One cannot but wonder if the motivation behind the proposed plan is not so much the worthy goal of accelerating human missions beyond Earth orbit, but rather the desire by at least some members of the Trump NASA transition team to establish the precedent that the SLS/Orion combination will be used for all human flights beyond Earth orbit. (I say some members because there is reportedly a healthy debate going on between those NASA transition team members who favor the government programs like SLS and Orion and those that favor commercial alternatives.)
There are many commercial alternatives to SLS/Orion on the horizon. In the super-heavy-lift launch vehicle category (payloads of 50 metric tons or more to low Earth orbit), four launch vehicles have emerged as alternatives to the SLS: SpaceX’s Falcon Heavy and Interplanetary Transport System, and Blue Origin’s New Glenn and New Armstrong. Two commercial crew capsules have emerged as alternatives to Orion: SpaceX’s Dragon 2 and Boeing’s CST-100 Starliner (though Boeing’s Starliner would need modifications to make it capable of lunar missions.)
|If this strategy were promptly adopted, we could not only see a crewed flight around the moon during Trump’s first term in office, but also see a human landing on the Moon and the beginnings of a lunar outpost by the end of Trump’s second term.|
My own belief is that we should go with the commercial alternatives to SLS and Orion. The commercial alternatives are more innovative and employ newer technology than the government solution. Both the developmental and operational costs to the taxpayer are a small fraction of that of the government programs. This is because the commercial programs are either being developed through private financing or through public-private partnerships, rather than the cost-plus contracts used for SLS and Orion. It is time for the government to stop competing with commercial space companies on programs that the commercial companies can do better, cheaper, and safer, since they will fly much more frequently.
The most effective way to move the space program forward would be to cancel the SLS and Orion programs and instead redirect the money spent on these programs to public-private partnerships like those that brought us the Falcon 9 and Antares launch vehicles and the Dragon and Cygnus commercial cargo vehicles. Public-private partnerships will also soon bring us the Dragon 2 and Boeing Starliner commercial crew capsules and the Dream Chaser commercial cargo spaceplane. If this strategy were promptly adopted, we could not only see a crewed flight around the moon during Trump’s first term in office, but also see a human landing on the Moon and the beginnings of a lunar outpost by the end of Trump’s second term.
Effective space policy only results through strong presidential leadership, leadership with the fortitude to reject pork barrel spending and pressure from special interest groups. It remains to be seen if President Trump is up to the task.