SpaceX has conducted their most successful test launch of a Starship system to date. The system they tested has three basic components – the Super Heavy first stage rocket booster, the Starship second stage (which is the actual space ship that will go places), and the “chopsticks”, which is a mechanical tower designed to catch the Super Heavy as it returns. All three components apparently functioned as hoped.

The Super Heavy lifted Starship into space (suborbital), then returned to the launch pad in Southern Texas where it maneuvered into the grasping mechanical arms of the chopsticks. The tower’s arms closed around the Super Heavy, successfully grabbing it. The engines then turned off and the rocket remained held in place. The idea here is to replicate the reusable function of the Falcon rockets, which can return to a landing pad after lifting their cargo into orbit. The Falcons land on a platform one the water. SpaceX, however, envisions many Starship launches and wants to be able to return the rockets directly to the launch pad, for quicker turnaround.

The Starship, for its part, also performed as expected. It came back down over the designated target in the Indian Ocean. Once it got to the surface it rolled on its side and exploded. They were never planning on recovering any of the Starship so this was an acceptable outcome. Of course, eventually they will need to land Starship safely on the ground.

The system that SpaceX came up with reflects some of the realities and challenges of space travel. The Earth is a massive gravity well, and it is difficult to get out of and back into that gravity well. Getting into orbit requires massive rockets with lots of fuel, and falls prey to the rocket equation – you need fuel to carry the fuel, etc. This is also why, if we want to use Starship to go to Mars, SpaceX will have to develop a system to refuel in orbit.

Getting back down to the ground is also a challenge. Orbital velocity is fast, and you have to lose all that speed. Using the atmosphere for breaking works, but the air compression (not friction as most people falsely believe) causing significant heat, so reentering through the atmosphere requires heat shielding. You then have to slow down enough for a soft landing. You can use parachutes. You can splash down in the water. You can use bouncy cushions on a hard landing. Or you can use rockets. Or you can land like a plane, which was the Shuttle option. All of these methods are challenging.

If you want to reuse your rockets and upper stages, then a splashdown is problematic as salt water is bad. No one has gotten the cushion approach to work on Earth, although we have used it on Mars. The retro-rocket approach is what SpaceX is going with, and it works well. They have now added a new method, by combining rockets with a tower and mechanical arms to grab the first stage. I think this is also the planned method for Starship itself.

On the Moon and Mars the plan is to land on legs. These worlds have a lower gravity than Earth, so this method can work. In fact, NASA is planning on using the Starship as their lunar lander for the Artemis program. We apparently can’t do this on Earth because the legs would have to be super strong to handle the weight of the Super Heavy or Starship, and therefore difficult to engineer. It does seem amazing that a tower with mechanical arms grabbing the rocket out of the air was considered to be an easier engineering feat than designing strong-enough landing legs, but there it is. Needing a tower does limit the location where you can land – you have to return to the landing pad exactly.

SpaceX, however, is already good at this. They perfected the technology the the Falcon rocket boosters, which can land precisely on a floating landing pad in the ocean. So they are going with technology they already have. But it does seem to me that it would be worth it to have an engineering team work on the whole strong-landing-legs problem. That would seem like a useful technology to have.

All of this is a reminder that the space program, as mature as it is, is still operating at the very limits of our technology. It makes it all the more amazing that the Apollo program was able to send successful missions to the Moon. Apollo solved these various issues also by going with a complex system. As a reminder, the Saturn V used three stages to get into space for the Apollo program (although only two stages for Skylab). You then had the spaceship that would go to the moon, which consisted of a service module, a command module, and a lander. On approach to the Moon, it would have to undergo, “transposition, docking, and extraction”. The command module would detach from the service module, turn around, then dock with the lunar lander and extract it from the service module. The pair would then go into lunar orbit. The lander would detach and land on the lunar surface, and eventually blast off back into orbit around the Moon. There it would dock again with the command module for return to Earth.

This was considered a crazy idea at first within NASA, and many of the engineers were worried they couldn’t pull it off. Docking in orbit was considered the most risk aspect, and if that failed it would have resulted in astronauts being stranded in lunar orbit. This is why they perfected the procedure in Earth orbit before going to the Moon.

All of this complexity is a response to the the physical realities of getting a lot of mass out of Earth’s gravity well, and having enough fuel to get to the Moon, land, take off again, return to Earth, and then get back down to the ground. The margins were super thin. It is amazing it all worked as well as it did. Here we are more than 50 years later and it is still a real challenge.

Spaceflight technology has not fundamentally changed in the last 50 years – rockets, fuel, capsules are essentially the same in overall design, with some tweaks and refinements. Except for one thing – computer technology. This has been transformative, make no mistake. SpaceX’s reusable rockets would not be possible without advanced computer controls. Modern astronauts have the benefits of computer control of their craft, and are travelling with the Apollo-era equivalent of supercomputers. Computer advances have been the real game-changing technology for space travel.

Otherwise we are still using the same kinds of rocket fuel. We are still using stages and boosters to get into orbit. Modern capsule design would be recognizable to an Apollo-era astronaut, although the interior design is greatly improved, again due to the availability of computer technology. There are some advanced materials in certain components, but Starship is literally built out of steel.

Again, I am not downplaying the very real advances in the aerospace industry, especially in getting down costs and in reusability. My point is more that there haven’t been any game-changing technological advances not dependent on computer technology. There is no super fuel, or game-changing material. And we are still operating at the limits of physics, and have to make very real tradeoffs to make it work. If I’m missing something, feel free to let me know in the comments.

In any case, I’m glad to see progress being made, and I look forward the the upcoming Artemis missions. I do hope that this time we are successful in building a permanent cis-lunar infrastructure. That, in turn, would be a stepping stone to Mars.