Comment by blackholesRhot | Hacker News Reader

Comment by blackholesRhot | Hacker News Reader

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FYI I'm a Spinlaunch invesetor.

Just watched this video. His argument for why Spinlaunch won't work is basically:

1) in the video of their first test chamber (12m diameter) there's some dirt and rust, therefore they don't know anything about vacuums

2) in their first ever test fire of a projectile leaving their 33m chamber, the projectile is wobbling, therefore they don't know anything

3) in a mock up video they made of a future launch system the headquarters is close to the launcher, which might explode if there's a misfire, therefore they don't know anything

4) the founder has an uninspiring resume when you look online

'Add these up and there's no chance they'll succeed. What they've done isn't as impressive as 50+ year old gunships.'

Give me a break. Their rate of progress is exceptional. They've already overcome so many challenges. These are weak arguments. Doesn't mean they'll be successful. But these arguments are weak. Some quick counter-arguments

1-) the 12m test chamber was a demo chamber. they were constantly spinning it up and letting people go inside. doing tours. stress testing new materials and arms. blowing stuff up. if anything the fact that it was so reliable even with the imperfections is a positive

2-) when someone is learning to throw a football there's tons of wobble. spinlaunch needs to figure out a perfect spiral. these videos were from their first couple attempts ever out of a chamber. what they're showing is very hard. this team has shown an ability to innovate and improve. those were images of their first few attempts to "throw the football"

3-) give the team some credit. these videos are designed for the general public. what they built already has an incredible amount of kinetic energy. they stress tested many tethers (past their limits) before going to this scale. when you're picking on things as small as "they're going to kill themselves by sitting right next to the system" you clearly don't have much left to nitpick

4-) jonathan is an absolute genius. just because he has a spartan online bio and unorthodox background doesn't mean he's not an absolute force of nature. thunderf00t is a very smart dude. but i'd bet anything that in a debate -- on basically any topic -- jonathan would absolutely decimate thunderf00t

cheers to the builders

>thunderf00t is a very smart dude

I just saw one of his videos on why Falcon 9 will never be economically viable so I would strongly disagree with this assessment.

I think his argument about Falcon 9 was about reliability vs reusability and he partially acknowledged he was wrong:

https://nitter.net/thunderf00t/status/961312911393218560?lan...

About the claim if he is smart or not, you might want to watch this then reevaluate your opinion:

https://youtu.be/5Hyy1zRZPiQ

The last video I watched of his was a debunking of flat earthers that was so bad it almost gave the flat earthers some credibility. Many of his 'debunkings' consisted of 'no, because science that's why' where the flat earthers had actually raised interesting questions where the answers provide a great jumping off point to explore things in more depth.

Taking ten years to come up with some simple experiments to debunk someone who is reasonably frequently publicly wrong and then labouring the point and being really condescending isn't a sign of someone being especially smart (although it's hardly stupidity either).

Its the typical build credibilty with debunking total nonsense and then use that to generate views on videos where he is suposidly depunking a lot more viable stuff.

Combine that with serving on the Anti-Musl wave and you have surefire way to be reddit famous.

Smart people make mistakes all the time. He has correctly debunked a lot of scams, it is easy to get jaded and carried away. Since he isn't an investor and doesn't have the inside scoop it is plain to see how his nitpicking, based on the publicly available information, potentially led him to a wrong conclusion.

SpinLaunch is a rather out there. I've actually had this idea and I'm sure many others have as well. I happen to think it can work but I was still skeptical when I first heard of them. You can only infer so much from the outside.

Thanks for the additional info blackholesRhot and for throwing money into this, the sort of bets we should be making. Godspeed. :)

The only thing that’s valid (and I didn’t really understand if the video maker understood it bc he wastes so much time on the wobble) is that if you spin sth up to, say, 200 /s, then your rocket will spin, with its full length, at 200 /s. I don’t know how they want to address that.

Cold gas thrusters.

That's barely enough for attitude control, do you have numbers how that could be used to despin a large rotating mass, as it is exiting the launcher?

I think you mis-understand the basics of how Spinlaunch is intended to operate.

The mass isn't rotating as it exits the launcher.

https://en.wikipedia.org/wiki/SpinLaunch

How could it not? The angular momentum is just disappearing?

Edit: Here's a link to an illustration, as your link provides zero information in that regard.

https://www.youtube.com/watch?v=TGO4LtCctTk&t=141s&ab_channe...

I clearly see their rocket rotate around its center of gravity, with the same angular velocity as the arm it's sitting on, while the center of gravity is moving on a circular path.

So, again, how is it not spinning? Where does the angular momentum go?

No, the better question is where it came from. The launcher spins the payload like a bucket on a rope. So upon exiting the launcher it isn't spinning. But by setting the guide vanes at a slight angle the payload can be made to spin to give it more stability (since this is essentially unpowered flight for the first bit) and it can be de-spun in the same way.

The launcher does not spin the payload around the long axis.

I can tell you exactly where it came from, it's being spun up in that launcher thing, obviously, that's the whole point of spin launch. You can see it for yourself in the video. Is the pointy end of the rocket always facing in the same direction, e.g. upwards? No, it's changing its orientation continuously, it's always facing 90 degrees from the arm of the launcher, which, you guessed it, spins.

It is indeed exactly like a bucket. And the bucket changes its orientation throughout you spinning it, that's the whole thing, that's why the water stays inside. The top side of the bucket is always facing you. For that to happen, it has to rotate around its COG with the same rate it's rotating around.

A different example: the moon is tidally locked to the earth (like the bucket to you, or the rocket to the spin launcher) - very obviously, it needs to spin around its axis to achieve that, and it does so at exactly the same rate as it is rotating around the earth.

That momentum doesn't just disappear.

SpinLaunch's website claims: "To date, we’ve conducted tests over 6x the speed of sound."

However, that doesn't seem possible because the centrifuge is not in a decent vacuum (as Thunderf00t points out in his second video) due to the whooshing sound of the centrifuge 'blade', and the speed can be estimated as just less than the speed of sound. If they have the ability to do hypersonic tests already, why would they not show it in their promotional video?

The fact that they intentionally blurred the data on the screens during the demo is also odd.

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Regarding your final point, it's much easier to pretend to be a genius than to actually be one; Elon Musk is a master at it. Additionally, debating skill is a very misleading measure of intelligence.

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