This has appeared a few times, and the basic physics critiques haven't changed.
It's one of those projects where it would thrill my inner sci-fi nerd to see it succeed... but not enough for me to disregard the reasons it probably won't.
Giant catapult sends satellites into space
41–50 of 61 posts
Re: Giant catapult sends satellites into space
#42There's some pretty fundamental problems with spin launch. Atmospheric drag is greatest at sea level, and drops as altitude increases. A traditional lift vehicle is traveling slowest during the early parts of its ascent, and starts reaching high velocity once it's cleared the thicker parts of the atmosphere. In contrast, spin launch is at its highest velocity (before the rocket engine ignites) right after it's releas…
SpacePort America, SpinLaunch's New Mexico test flight facility, is at ~5000' above sea level. If drag is a serious limitation, they could potentially see additional gains by relocating their launch facilities to a city in e.g. Peru. My understanding is the atmospheric density is about 25% lower above 12K feet compared to sea level and about 15% lower than at 5K feet and there are a handful of places with road networ…
According to [1], density at 30,000ft is 35% of sea level. So you could bore an elevator up Mount Everest.
Re: Giant catapult sends satellites into space
#43There's some pretty fundamental problems with spin launch. Atmospheric drag is greatest at sea level, and drops as altitude increases. A traditional lift vehicle is traveling slowest during the early parts of its ascent, and starts reaching high velocity once it's cleared the thicker parts of the atmosphere. In contrast, spin launch is at its highest velocity (before the rocket engine ignites) right after it's releas…
I don't see how this will work. You need to launch through the entire atmosphere and still end up with orbital velocity. The only acceleration happens at the beginning so you must launch at speeds much higher than orbital speeds. Which in turn means heating will be insanely high as your highest speed is going to be at the highest drag. The satellite will heat up a lot more than one simply re-entering. Meaning a total…
Insane g-force in the spin up.
Reminds me of Gerald Bull who wanted to launch a satellite using a huge artillery piece.
Re: Giant catapult sends satellites into space
#44From what I can tell looking at SpinLaunch's website and web search, they were founded in 2014, "launched" a couple projectiles in atmosphere, had a leadership change in 2022, and have been pretty quiet since then. Unless I've missed something, the headline "Giant catapult sends satellites into space" is not true. To date, they have not put anything into orbit and the company appears to be on life support.
From what I could find they have only reached 1/10th of the Karman line. I also think its a red flag that they do not have actual press releases or data, just a list of any random website that wrote a story about them.
I think it's a red flag that a company is so willing to blatantly lie in public-facing communication.
Re: Giant catapult sends satellites into space
#45Earlier quoted context omitted.
I wonder what would be the technical challenges of a railgun powered rocket/capsule to launch small payloads to space, technically the remaining concern would be the G force from the acceleration.
Railguns have always suffered from rail degradation. Basically even if you build a suitably large one, you might get as few as 1 shots from the structure before having to replace the entire rail.
The railgun "solution" occurred to me too. Is the rail degradation a failure of materials science? Or are the materials that would be required for this so theoretical at this point to be science fiction rather than science?
Re: Giant catapult sends satellites into space
#46This has appeared a few times, and the basic physics critiques haven't changed. It's one of those projects where it would thrill my inner sci-fi nerd to see it succeed... but not enough for me to disregard the reasons it probably won't.
⬆ this
Re: Giant catapult sends satellites into space
#47There's some pretty fundamental problems with spin launch. Atmospheric drag is greatest at sea level, and drops as altitude increases. A traditional lift vehicle is traveling slowest during the early parts of its ascent, and starts reaching high velocity once it's cleared the thicker parts of the atmosphere. In contrast, spin launch is at its highest velocity (before the rocket engine ignites) right after it's releas…
I don't see how this will work. You need to launch through the entire atmosphere and still end up with orbital velocity. The only acceleration happens at the beginning so you must launch at speeds much higher than orbital speeds. Which in turn means heating will be insanely high as your highest speed is going to be at the highest drag. The satellite will heat up a lot more than one simply re-entering. Meaning a total…
It is not possible to go into orbit from a single speed boost at the surface, even without an atmosphere, because the "orbit" would still contain the starting point. In other words, the orbit would intersect with the surface of Earth. (Well, unless you go all the way to escape velocity.) To fix this, an additional "apogee kick" is needed.
The Spinlaunch concept is to get a small rocket + payload to 60 km altitude. Then the rocket would fire and actually put the payload in orbit.
The catapult would only provide up to 2 km/s out of the ~ 10 km/s or so required to get to orbit. Saving those 2 km/s of rocket delta-v could be significant, because rocket size goes up exponentially with delta-v.
Re: Giant catapult sends satellites into space
#48There's some pretty fundamental problems with spin launch. Atmospheric drag is greatest at sea level, and drops as altitude increases. A traditional lift vehicle is traveling slowest during the early parts of its ascent, and starts reaching high velocity once it's cleared the thicker parts of the atmosphere. In contrast, spin launch is at its highest velocity (before the rocket engine ignites) right after it's releas…
I could see it being a great option for getting bulk goods into space. Fuel, water, food, spools of wire or powders for additive manufacturing, structural components, etc. Depends on what is cost effective. The difficult part would be catching the payloads. It would probably be an even better option on lower gravity lower atmosphere celestial bodies.
When you have low gravity and little atmosphere, I can't imagine many scenarios where a spin launcher would be a better fit than a mass driver. One of the biggest problems with a mass driver on Earth is that you need to do it in a vacuum over a huge area, which isn't a problem with - say - launching from the moon. The spin launch approach makes some sense on Earth, given that you only have to build a (relatively) small vacuum chamber and a very well-timed airlock to let the payload get into the atmosphere.
But the counterweight issues, extreme G forces during spin-up, etc make it kind of a non-starter in my mind for other bodies; I'd love to hear arguments for it vs simple mass drivers off Earth.
Re: Giant catapult sends satellites into space
#49There seem to be a lot of businesses like this one: well-funded by VC money, but trying to do things that are scientifically questionable. This reminds me a bit of Helion Fusion, which is supposed to produce commercial power by (I think) 2029? Something seems a bit wrong with our VC markets if stuff like this is getting funded.
machining and fabrication feels exciting and empowering, almost intoxicatingly so, when you first start. all the construction machinery, engineering, material science, logistics, it seems very important. it feels like you are definitely doing something cool and important. well, not you, but the people you hired. so its almost you, kinda, like, if you squint. but eventually you might find out that you have to actually have an understanding and knowledge of the subject that exceeds just about everyone else if you want to do something useful. but until the failures start rolling in and the money dries up, you can pretend you are cool.
Re: Giant catapult sends satellites into space
#50Much as I might like to see alternate ways of launching succeed, I have always thought that physics was not on their side.