NASA chief explains why agency won't buy a bunch of Falcon Heavy rockets [arstechnica.com]
Since the launch [arstechnica.com] 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 [arstechnica.com], 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 [arstechnica.com] 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 [spacex.com] 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 [spaceflightinsider.com] of the Lunar Orbital Platform-Gateway [wikipedia.org] (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 [wikipedia.org] 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.
Related: NASA Eyeing Mini Space Station in Lunar Orbit as Stepping Stone to Mars [soylentnews.org]
NASA and Roscosmos Sign Joint Statement on the Development of a Lunar Space Station [soylentnews.org]
President Trump Signs Space Policy Directive 1 [soylentnews.org]
Russia Assembles Engineering Group for Lunar Activities and the Deep Space Gateway [soylentnews.org]
After the Falcon Heavy Launch, Time to Defund the Space Launch System? [soylentnews.org]
President Trump Praises Falcon Heavy, Diminishes NASA's SLS Effort [soylentnews.org]