One of the comments we received on a recent article about Elon Musk’s plans for Mars stated that SpaceX’s plans for the Big Falcon Rocket were “nonsensical fantasy” so we thought we’d have a closer look at what NASA is planning with the Space Launch System (SLS) as a comparison. The big difference is the SLS is government funded and run by NASA, who have a long pedigree of successful space ventures including putting people on the Moon and countless other achievements. The SLS programme was born out of the cancelled Constellation programme and is a kind of replacement for the Space Shuttle. It has four components, the main stage, the payload and second stage and the boosters and all together will be the most powerful rocket ever built when it flies in 2019 on Exploration Mission 1. It’s a key part of the the US plan to get humans to Mars and a key part of the the construction of the Lunar Orbital Platform-Gateway that will orbit the Moon.
The construction of the SLS is well underway, with the rocket engines for the core and second stage being successfully tested. They are the same engines that were used on the Space Shuttle, so are proven and are reliable, the RS-25. The engines have also been upgraded and had new components added. The main difference is that these engines are expendable and will not be recovered from the core stage. Other components already under construction include the structure of the core stage, a bit called the intertank and the infrastructure at Cape Canaveral to support the launch.
The first launch will be called Exploration Mission-1 (EM-1). This mission will combine all of the components of the SLS including the the Orion capsule, the bit missing of course, is that it will have no people. The planned mission is to launch the Orion spacecraft to beyond the Moon and hang around for about three weeks in total. The rocket will produce about 8.8 million pounds of thrust at liftoff. The plan is for the spacecraft to do one orbit of the Earth and then the Interim Cyrogenic Propulsion Stage will fire to give the Orion the kick it needs to head to the Moon. Attached to the Orion spacecraft will be a service module produced by the European Space Agency. The trip to the Moon will take a couple of days and when it gets there, the spacecraft will fly about 100km above the surface and then be propelled into an orbit around the Moon at about 70,000km from the surface. Orion will stay in that orbit for about six days before heading back to the Earth. The re-entry of the spacecraft will be at nearly 11km per second and it’s heat shield is expected to reach temperatures of nearly 2760 degrees.
The next mission will be crewed and over time the SLS will be used to construct the Lunar Orbital Platform-Gateway. Then future missions will dock with the platform and other missions will be conducted to the lunar surface. This first crewed mission will take humans further than they have ever been before. The profile will be to circle the Earth a few times, gaining speed then head to the Moon for an orbit and then back to the Earth. The diagram below explains it pretty well:
The actual journey to Mars is not anticipated to happen until the 2030s. NASA wants to go there slowly via the Moon, then deep space and then to Mars. There’s a lot to figure out on such a long trip, including getting to understand how the human body will handle the stresses of deep space for long periods of time. The wealth of information collected by rovers has enabled scientists to better understand the radiation that astronauts will be exposed to and planned rovers and other missions will help gain a better understanding of the possible resources that may be available on the Martian surface. NASA wants to use the missions to the Moon as a proving ground for the technology to go to Mars. During the 2020s astronauts will hop into the Orion spacecraft and blast off on a year long mission into deep space helping to verify the safety of spacecraft systems and the effects of long term space travel on the astronauts.
Part of the plan is called the Asteroid Redirect Mission in which an asteroid will be captured and then the astronauts from the Orion spacecraft will explore it. The aim of this component of the mission is to test space walking, testing and sampling techniques. NASA wants to also test Solar Electric Propulsion which is intended to be used to help get cargo to and from Mars. NASA describes the phases of getting to Mars in three categories; Earth reliant, Proving ground and Earth independent. Compared to the plans that SpaceX has, the NASA plans are much slower with more deliberate steps to test safety on the spacecraft and on the astronauts. It could be nearly twenty years before humans set foot on Mars based on NASA’s plans, which is probably why so many are excited by the prospect of what SpaceX is planning and the possibility of humans getting there earlier.