Jonathan Goff’s First Take on SpaceX’s ITS

Jonathan Goff wrote a nice blog post that’s really worth reading. He goes in-depth on what he likes, what he doesn’t like, what he’d do differently, and discusses his thoughts on the economics of the plan. Some highlights:

Trying to make the ITS do so much doesn’t bode well to me for keeping it affordable. We’re talking a near-SSTO performance level reusable upper stage, who’s ascent and landing propulsion has to double as a rapid-response launch abort system, with a what amounts to a 100 person space station on top of it. Many SpaceX fans seem to think that slapping more requirements onto the most challenging piece of the overall architecture will somehow save costs compared to developing two or three more optimized system elements, but I’m really, really, really skeptical. This seems like repeating one of the dumbest mistakes from the Space Shuttle.

The “Look how much this single unit can do!” mantra does have quite a bad history when it comes to spaceflight. Bad memories.

On the landing gear-less BFR:

We could totally build jetliners today without landing gear, using landing trolleys or other things. Or fighter jets landing on sleds on carriers. But we don’t because there’s no way aircraft would be as reliable as they are without having things like landing gear that give them options when something goes off-nominal. Let me put it this way–I don’t think you’re likely to ever see an RLV design that can survive long enough to average 1000 reuses (like SpaceX has baked into their BFR economics) without including landing gear.

On using a separate TMI and/or TEI stage:

It probably makes sense to have a separate TMI propulsion system that does the equivalence of a boostback maneuver after the TMI burn is done, to decelerate back into a highly-elliptical Earth orbit, where it can then aerobrake back to LEO. By not sending that along with the transfer hab, you enable it to be reused a lot more, since it’s not tied up for four years now. While not doing transfers to Mars, it can be sending payloads to/from Cislunar space, or to/from GEO.

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The more of your architecture is in the “can get 100+ flights in its lifetime” category vs “synodics mean I can only fly 12x in my lifetime” category, the cheaper things will be overall.

The whole post is really worth reading through, so go check it out.