from the up-in-the-air dept.
Exploration Mission 2 using the Space Launch System was originally planned to launch using the Block 1B version, which includes the Exploration Upper Stage and can carry 105 metric tons (105,000 kg) to to low-Earth orbit. Now that Congress has given NASA additional money for a second SLS mobile launcher, the agency has the ability to fly astronauts on the smaller Block 1 version of SLS, capable of lifting 70 metric tons to LEO:
The SLS has been in development for the last decade, and when complete, it will be NASA's main rocket for taking astronauts to the Moon and Mars. NASA has long planned to debut the SLS with two crucial test missions. The first flight, called EM-1, will be uncrewed, and it will send the smallest planned version of the rocket on a three-week long trip around the Moon. Three years later, NASA plans to launch a bigger, more powerful version of the rocket around the Moon with a two-person crew — a mission called EM-2.
But now, NASA may delay that rocket upgrade and fly the same small version of the SLS for the crewed flight instead. If that happens, NASA would need to come up with a different type of mission for the crew to do since they won't be riding on the more powerful version of the vehicle. "If EM-2 flies that way, we would have to change the mission profile because we can't do what we could do if we had the [larger SLS]," Robert Lightfoot, NASA's acting administrator, said during a Congressional hearing yesterday [2h15m22s video].
[...] Meanwhile, it's also possible that the second flight of the SLS won't carry crew at all. NASA also needs to launch its upcoming mission to Jupiter's moon Europa pretty soon. Known as Europa Clipper, the mission is mandated by Congress to fly on the SLS by 2022. Lightfoot mentioned that Europa Clipper could come before the first crewed flight of the SLS. It just depends on if the Orion crew capsule, which will carry astronauts on the SLS, is ready before Europa Clipper is ready. If the Europa spacecraft comes first, then it could also fly on the small Block 1 rocket.
The trans-lunar injection (TLI) payload capacity for SLS Block 1B is 39.2 metric tons, enough to carry a ~25.9 ton crewed Orion capsule with an 8-10 ton component of the Lunar Orbital Platform-Gateway (LOP-G), as was the original plan for Exploration Mission 2. Block 1 cannot accomplish these two tasks at the same time. Perhaps they should launch LOP-G using Falcon Heavy instead?
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Congress has given NASA $350 million for a second mobile launcher for the Space Launch System:
The problem stems from the fact that NASA's current mobile launch platform wasn't actually built for the SLS. NASA has been modifying a platform that was originally built for a rocket that never saw the light of day — the Ares 1, a vehicle that was meant to send humans back to the Moon as part of the now-canceled Constellation program. When the Constellation program was replaced with the SLS program in 2011, NASA decided to simply upgrade the mobile launch platform the agency had already built for Ares 1 to support the Space Launch System. The SLS is a much bigger and heavier vehicle than the Ares 1 was going to be, so NASA has had to reinforce the base of the platform, as well as expand it to accommodate the larger size of the rocket and its engines.
[...] Now, Congress is telling NASA to build a second platform, likely due to safety concerns. Building the new platform could potentially move the second flight of SLS up to 2022 instead of 2023. Otherwise, having such a huge gap between the first and second flight of the rocket could cause engineers to forget the valuable experience they gained from flying the rocket the first time. "When that happens, you have all the people — in your ground systems and in mission control — you have them sitting around for months at a time with nothing to do," Casey Dreier, director of space policy at the Planetary Society, tells The Verge. "And in the absence of real rocket launches, you might lose good people."
But another unofficial motivation could be optics. Further delays would be a bad look for the perennially delayed SLS program. The first flight of the SLS has been consistently pushed back — from 2018, to 2019, and then to 2020. And even when the first two flights of the vehicle are done, the rocket will probably only launch once a year.
Lawmakers provided $150 million for the Wide-Field Infrared Survey Telescope, or WFIRST, which the Trump administration proposed canceling last month. Set for launch in the mid-2020s, WFIRST would be next in NASA's line of big observatories in space after Hubble and the James Webb Space Telescope. It was the top priority for NASA's astrophysics program in a National Academy of Sciences decadal survey released in 2010. The agency's policy is to follow cues from the science community encapsulated in the decadal survey reports.
Agency managers last year were wary that WFIRST could exceed its $3.2 billion cost cap, and Thomas Zurbuchen, head of NASA's science directorate, in October ordered a team at the Goddard Space Flight Center in Maryland — home of the WFIRST project office — to study how the mission could be modified to fit under the budget limit.
Officials drafting NASA's budget request for fiscal 2019 decided WFIRST was too expensive, but the mission has enjoyed strong support from Congress. In an apparent reference to WFIRST's proposed termination, lawmakers wrote that they "reject the cancellation of scientific priorities recommended by the National Academy of Sciences decadal survey process."
Since the launch of the Falcon Heavy rocket in February, NASA has faced some uncomfortable questions about the affordability of its own Space Launch System rocket. By some estimates, NASA could afford 17 to 27 Falcon Heavy launches a year for what it is paying annually to develop the SLS rocket, which won't fly before 2020. Even President Trump has mused about the high costs of NASA's rocket. On Monday, during a committee meeting of NASA's Advisory Council, former Space Shuttle Program Manager Wayne Hale raised this issue. Following a presentation by Bill Gerstenmaier, chief of human spaceflight for NASA, Hale asked whether the space agency wouldn't be better off going with the cheaper commercial rocket.
[...] In response, Gerstenmaier pointed Hale and other members of the advisory committee—composed of external aerospace experts who provide non-binding advice to the space agency—to a chart he had shown earlier in the presentation. This chart showed the payload capacity of the Space Launch System in various configurations in terms of mass sent to the Moon. "It's a lot smaller than any of those," Gerstenmaier said, referring to the Falcon Heavy's payload capacity to TLI, or "trans-lunar injection," which effectively means the amount of mass that can be broken out of low-Earth orbit and sent into a lunar trajectory. In the chart, the SLS Block 1 rocket has a TLI capacity of 26 metric tons. (The chart also contains the more advanced Block 2 version of the SLS, with a capacity of 45 tons. However, this rocket is at least a decade away, and it will require billions of dollars more to design and develop.)
SpaceX's Falcon Heavy TLI capacity is unknown, but estimated to be somewhere between 18 and 22 tons (between the known payloads of 16.8 tons to Mars and 26.7 tons to geostationary orbit).
Does the SLS need to launch more than 18 tons to TLI? No. All of the currently planned components of the Lunar Orbital Platform-Gateway (formerly the Deep Space Gateway) have a mass of 10 tons or less due to flying alongside a crewed Orion capsule rather than by themselves. Only by 2027's Exploration Mission 6 would NASA launch more massive payloads, by which time SpaceX's BFR could take 150 tons to TLI or even Mars when using in-orbit refueling.
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