Framing It: September 3, 2019
This week saw the test of the Starhopper, a squat little stainless steel can of a rocket and the testbed for SpaceX’s next rocket system, the Big Friggin Rocket:
The Starhopper is only just a prototype, and quite similar to another SpaceX project from nearly a decade ago, the Grasshopper. Where the Grasshopper served as a test platform for the vertical landing Falcon 9 rocket, the Starhopper is the beginning of something much bigger: the BFR, the interplanetary Mars transport system that will most likely be the first rocket to take a human to Mars.
The Starhopper is done, it’s served its purpose, and now this gigantic squat tube of stainless steel is going to a museum or parking lot or something. SpaceX’s next big thing is the prototype of the actual Starship. That’s being built right now in Florida, and there might be a test flight to 20km sometime in October. Elon will be presenting on the future of the Starship on September 28th (location TBD).
A Gigantic New Rocket
The Starship and BFR aren’t the end-game for SpaceX, because taking a cruise ship to Mars isn’t quite enough for Elon. There is now news of what will come after the BFR. Sure, it’s just a tweet (‘funding secured’, ‘genetically engineered cat girls’), but there are plans in the works for an 18 meter diameter rocket.
An 18 meter diameter rocket is, simply, crazy. From the choice of diameter of the rocket, we can infer a lot about what this now theoretical rocket will be capable of. You can estimate the length of a rocket to be somewhere between 12–18 times the diameter, so this Really BFR would have a height of around 260 meters, or 850 feet. Assuming that, this fictional rocket should be able to launch one thousand tons into orbit.
Is this the largest rocket ever designed? No, not quite. In the heady days of the space race, an engineer at Aerojet came up with the Sea Dragon. This was a rocket 500 feet long and 75 feet across. There was no launch pad, it was simply floated out to the middle of the ocean, filled with fuel, partially submerged, and exploded out of the water:
The Sea Dragon never got off the ground (or out of the sea) because there was simply no need for it. The United States wasn’t going to Mars in the 1980s, and there would be no massive space station built.
But now that it looks like we’re going to Mars, we need a way to get cargo there. A lot of cargo. Oh, and there’s one more thing a huge rocket can do: lift really big things.
Somewhere in Baltimore, a scientist is crying
The James Webb Space Telescope has been fully assembled, and it looks awesome. It’s the next space telescope after the Hubble is finally decommissioned, and it’s huge: JWST has eighteen hexagonal mirrors that will fold out in orbit, and a final mirror diameter of 12 meters. The folding and unfolding mirrors are a result of the launch vehicle; you simply can’t launch a single mirror that’s 12 meters in diameter because it won’t fit on a rocket.
While JWST due to launch in early to mid-2021, SpaceX is planning the first launch of the BFR would be just a few months later, by 2022 at the latest. Yes, the mirror for JWST, if it launched on a BFR, could have been made in one piece. It could have been made even bigger if you wanted bigger hexagonal panels. Somewhere at Johns Hopkins Applied Physics Lab, there’s an engineer crying.
