SpaceX is nothing if not ambitious. They’ve always said that their long term intentions are to make their boosters, the Falcon 1 & Falcon 9, reusable. But they’ve never really detailed just how they intend to do so. I think most people presumed they’d use parachutes and either splashdowns and water recovery or a land recovery with airbags or something similar.
But that’s not ambitious enough for SpaceX, oh no. They want to use powered recovery. They plan to use aerodynamic lift and the rockets to fly the boosters back to the launch site and make a vertical landing. They’ve released the following video of a simulation of the process.
The rocket in the video looks like an updated version of the Falcon 9 with three larger main stage engines instead of the nine on the current design. Since the first stage never leaves the atmosphere, and is travelling at a much lower speed when its job is complete, it doesn’t need much thermal protection.
The first stage flips end for end and uses thrust to arrest the motion and then fly back to the launch point. That’s similar to the Return To Lauch Site abort profile for the Space Shuttle, which would’ve used the main engines to return to the cape once the solid rocket boosters burned out. There have also been similar concepts such as fly back boosters using wings and jets, but that adds a lot of weight.
The second stage does continue to orbit with the payload. So it continues around the earth and performs a de-orbit burn to reenter. The nose of the stage is a heat shield, I’d guess based on the one they’re using on the Dragon capsule. The stage decelerates using aerobraking and flies back to the launch site primary as a lifting body. Once most of the way there it uses the engine thrust for the final braking and controlled flight to a vertical landing.
The Dragon capsule discards its service stage in orbit, leaving it to burn up on reentry as the one major expendable component. Then it reenters and lands much like the second stage. The thrusters used for landing double as the emergency abort system for launch.
Yes, this means carrying more fuel to launch a given payload than you need with an expendable booster because you need a reserve used for landing. It also means that for a given thrust level you have a lower throw weight, or payload to orbit, because you’re carrying the extra fuel mass. Conversely to place the same payload in orbit you need a larger booster.
So, that’s bad right? Not really. Rockets are expensive. Very, very expensive. A Falcon 9, which is one of the least expensive rockets in its class, costs $50-60 million dollars. Fuel is cheap. The cost of RP1 (basically kerosene) and LOX or a Falcon 9 launch is approximately $200,000. (Figures from the C-Span video below, about 21 minutes in.) $200,000 may not sound ‘cheap’, but compared to the hardware it is nothing. If you can reuse the hardware repeatedly the savings add up and justify the increased fuel costs.
It might sound like a crazy idea, but remember that vertical powered landings have been used many times for landing on other bodies. A number of planetary and lunar probes have used a powered landing, and, of course, all of the moon missions used a lunar lander that made a powered descent and landing. On Earth the McDonnell Douglas DC-X developed the vertical launch & landing concept before it was cancelled. The concept lives in and vertical launch & landing designs have been created and flown by Blue Origin, Armadillo Aerospace, Masten Space Systems, and others.
It is certainly possible to do. It isn’t simple, but it isn’t unfeasible. And if anyone can pull it off, it is probably SpaceX. I think they’ve the most exciting company to watch in the rocket industry at the moment.
SpaceX CEO Elon Musk talks a bit about their plans in the following C-Span video, starting around 20 minutes in. Note that he says the video above is not a completely accurate representation of their concept. This is partly due to the concept evolving and the video not representing the latest evolution, and partly due to deliberately hiding some of their technical points for competitive reasons. So take it as an example of the concept and not an exactly depiction.
Picked up via Gizmodo.