Space and Science BS Thread

Scott Manley looked into it and came up with ~10,000 g at peak loading before launch. That’s based on Mach 6-7 and 100 meter diameter. He mentions the need to build both the rocket and payload to withstand that load and also brings up how the rotating arm becomes unbalanced at the moment of launch but still seems optimistic (or at least less pessimistic than I). It still seems insanely complex to deal with balancing, release point, and vastly greater stress levels and they also want to tilt the axis 35 degrees off plumb but it is something they can study in a relatively small facility.

 

Get out of my head! Just watched that video.

 

I still think a "cannon" barrel where the projectile is the scramjet engine is a better way to go.

 

https://twitter.com/nasakennedy/status/1458972676408684553?s=21


SpaceX- 18 individuals flown to space in 5 missions over the past 18 months.

 

It's not impossible. We are after all only talking about a 200kg payload capacity. That's more than 1,000 times less than the capacity of falcon 9, 100kg less than Rocket Lab's current offering. The forces should be less than Scott's calculations, though how much is hard to calculate as there are no real numbers out there. Some articles say the test ring is 165ft, some say 100 meters, some say 30 meters. Many say it is taller than the statue of liberty, that would coincide with 100meters, and with that being 1/3 scale the finished product could be 300 meters in diameter.

As for building satellites to match their launch systems, this is nothing new to the industry. Many satellite manufacturers started adding more ion thrusters to their satellites so that they could use the falcon 9 instead of much more expensive, but more capable rockets that would have put them closer to the orbit they needed.

 

Remember when Boeing and Spacex were "neck and neck" for being the first private companies to launch people? At least those times felt kinda exciting...

 

Any particular reason? Some kind of second stage seems appropriate but why that type of launch mechanism?

 

Edit -200kg doesn’t include the rocket stage and fuel necessary to finish the job of orbital insertion.
Run some numbers yourself, 10,000g’s is right in the ballpark
I did the math to show that even with a 1000’ radius the forces of a rotating sling are extreme, not just by a small amount easily compensated for with satellites made a bit more stout. It’s not a complex equation, you can plug in any size or exit speed and come up with the result. By the time a radius of rotation gets large enough to bring g-forces to a manageable level you might as well just build some kind of linear launcher up a mountain instead, it would end up being a smaller construct and not have to deal with any g-force other than straight line acceleration. The redesign necessary to accommodate thousands of g’s can’t be trivial, or cheap since they are typically exposed to no more g’s than astronauts. Scott did point out though that it would be a lot more practical as a lunar based launcher instead for certain cargoes.

 

The problem comes into to actually building the launcher. Assuming they're using something along the lines of mag lev, they only need about 6,000 feet of propulsion apparatus. If they can't make it go fast enough in a single rotation they just let it to another rotation and pick up more speed. Building a several mile long barrel and keeping it perfectly straight up the side of a mountain would be very difficult. Even harder to maintain because mountains are created by tectonic plates colliding and moving. I'm pretty sure no matter how good carbonfiber is, if it even grazes the side of a barrel at mach anything, bad things are going to happen.

 

They were talking about spooling up to speed over the course of hours not one or two rotations. It’s not maglev, it’s an arm that rotates on an axis like one hand of a clock with a release mechanism at the end of it. Hold a rock, windmill your arm, and let go is the essence of the idea. Withstanding g forces that grow exponentially over that time doesn’t strike me as preferable over using maglev which has been around for decades for alignment, adds no extraneous forces and has much more room for deviation as well as much higher payload capacity both in terms of weight and delicacy. Keeping that hypersonic rotating mechanism balanced after suddenly letting go of the mass at the end is another issue that arises in the video, as is achieving an absolutely perfect release point. I would argue that stability is even more critical and harder to achieve at the necessary level of precision for a sling than for something linear that can self center as it transits.
I’m not saying it’s useless, it would be great for tossing resupply loads up to orbital space stations. I am saying that windmilling introduces an exponential increase in loading that results FROM speed but does not result IN speed. I don’t see it as a brilliant idea even though brilliant engineering may come from it.

 

How much have these guys raised in capital? A fool and his money…

 

Having an arm does not mean they're not using maglev to spin it. It just means that they have a rigid attachment that guarantees the capsule never touches the walls of the launch system. Maglev alone however won't achieve this. Maglev trains touch the tracks while running all the time. Usually it's just a bump and only for a second, and doesn't effect anything because the carriage has wheels for this exact purpose, but they are only going 2-300 mph, not the 5,000 spinlaunch is aiming for. But the biggest problem is length. For every turn of the arm, their rocket capsule has traveled over a mile. If it is taking them hours to achieve the desired speed, then that rocket has already traveled thousands of miles before it has left the launch system. Comparing that to a barrel. Mt everest is 6 miles high (not going to happen, but best case scenario). So a rocket would have to go from 0-5,000mph in 6 miles, or the equivalent of 5 rotations of Spinlaunch's system. I don't believe there is an electric propulsion system currently that could even come close to that. A maglev train for example takes 3 miles to accelerate to 180 mph.

 

https://www.nationalacademies.org/documents/embed/link/LF2255DA3DD1C41C0A42D3BEF0989ACAECE3053A6A9B/file/DA165654195CEAF8970F8B9A1EDE3C0D0DD7506E89BB

Lotsa recognizable speakers and subjects. Elon’s speaking on Starship the last day.

 

https://twitter.com/sierraspaceco/status/1459172165941665799?s=21

 

Looks like the whole thing is gonna blow kinda like a Delta IV...

https://twitter.com/spacex360/status/1459210186007228420?s=20


A first
https://twitter.com/NASASpaceflight/status/1459223181684838403?s=20
https://twitter.com/elonmusk/status/1459223854757277702?s=20
https://twitter.com/SciGuySpace/status/1459243882420621317?s=20

 

Wasting no time... (Spoiler - it's Tom and Kayla)

https://twitter.com/Space_Station/status/1459219167907885056?s=20

 

It’s also a train several times the size of any multistage rocket, not a small capsule. Not doing something because it’s not necessary is not the same thing as not being able to do it. But if it’s impossible to keep it from bumping how much harder would that be for the rotating shaft when the lateral forces are exponential instead of minimal. This “train” would never have to go up, down, or sideways, just be guided in a straight line for a relatively short distance. I don’t think either one is currently feasible but the small size of the sling makes it seem more attractive. A brilliant idea takes advantage of some principle in a manner that creatively reduces or eliminates other problems, this rotation introduces forces perpendicular to the desired velocity exponentially. It places a burden on payloads and the launch mechanism to be not just several times stronger but several orders of magnitude stronger. Applying an increase in capsule and payload strength of a single order of magnitude shortens a straight track to under 2 miles instead of almost 20. Straight line acceleration is much more straight forward and the problems presented are solvable at orders of magnitude lower levels of engineering. It’s interesting science though.

 

You look like a fairly young man, you may live to see it launch, me, I'm not so sure

 

I'll be on the roof of the VAB when she goes, I've got a lot of blood and sweat tied up in that rocket.

I opened the valve that sent Hydrazine downstream to the Orion capsule. Pretty proud of that.

 

This was a really cool shot live, only up for a second or two..

https://twitter.com/nasaspaceflight/status/1459493888691945478?s=21

https://twitter.com/launchphoto/status/1459610813363326977?s=21

https://twitter.com/spacex/status/1459496546047717382?s=21