Giant catapult sends satellites into space | Hacker News Reader

Giant catapult sends satellites into space

spinlaunch.com

45 pointsjv2222257 comments

From 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.

SpinLaunch built a prototype back in 2022 that can throw stuff up to suborbital altitudes. The big version was supposed to be done by now. They had a lot of trouble finding a launch site. Hawaii didn't like it. Alaska didn't like it. Australia was discussed but nothing happened.[1]

This might be useful if there were space stations that needed large, frequent deliveries of fuel, air, and water.

[1] https://thespacebucket.com/what-happened-to-spinlaunch-its-p...

I think it's a red flag that a company is so willing to blatantly lie in public-facing communication.

They'd have got there already if they'd built a space trebuchet instead of a space catapult.

I think the idea was technically a space trebuchet, but the energy for launch is stored in a flywheel. It's still far too little energy to do anything real.

There'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 released, so it's going to bleed off a lot of speed before it reaches the upper atmosphere.

Second, spinning exerts very heavy lateral Gs on the vehicle and load. This is not typical for space launch payloads, which are usually only designed to withstand vertical Gs. When the catapult releases the payload, atmospheric drag is going to put heavy vertical Gs on the payload. So a payload delivered through spin launch is going to have to withstand both lateral and vertical Gs.

Its an interesting concept, but I'm not sure if the advantages of this approach outweigh the disadvantages.

I do see a future use case for spin launchers based in vacuum, say, on the moon. Or maybe on Mars where atmosphere is much thinner.

You got the basic physics, but don't you think they have considered these issues? It's why this is interesting at all : despite the very obvious difficulties they think this has a case.

First time i saw this i thought it must be people who do actually know their stuff. But then they realized it can not be done and decided to have fun while scamming investors.

> spin launch is going to have to withstand both lateral and vertical Gs.

I wonder if there is a trick to rotate the craft between disconnection and hitting the atmosphere so that the forces are in the same direction for both?

You would have to do the rotation in the short straight section in the vacuum chamber after it is released from the centrifuge. The craft is traveling extremely fast at this point and you only have maybe 50m or less to do the rotation. I think doing a 90 degree rotation in this timespan (25ms or so, because you’re traveling at 2km/s) would need extreme rotational acceleration which wouldn’t be much gentler on the craft, and you would need some system that can actually achieve this rotation in this short time.

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.

IMO Kantrowitz laser propulsion seems more practical for that https://www.niac.usra.edu/files/studies/final_report/897Kare...

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 networks that go that high

According to [1], density at 30,000ft is 35% of sea level. So you could bore an elevator up Mount Everest.

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?

There's nothing fundamentally impossible AFAIK - i.e. the rail itself doesn't have to do anything it can't, but you need the surface to survive enough shots to make it worthwhile.

For an actual weapon, this is potentially worth it at a pretty low number since the weapon itself will be pretty small. For a rocket accelerator sled this is going to be more of a problem (but like, conversely you could consider ideas like re-surfacing the rails in place since your turn around isn't fast).

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 totally different design or a bulky fairing. Because sats aren't made to withstand that kind of heat. Also yes the forces will be extreme. They seem to be going for the fairing, but how does that reenter then?

I just don't see this happening tbh.

Besides, with spacex and reusability launch capacity is already more available and cheap enough than humanity needs.

You're missing the fact there's a second stage.

Insane g-force in the spin up.

Reminds me of Gerald Bull who wanted to launch a satellite using a huge artillery piece.

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

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.

It's good for some kinds of load, just need to know which kind

Orbital accelerators are cool, IMO they feel much more sci-fi than rockets (and still a step below space elevators). They're not without their tradeoffs, though: the G-forces involved mean they're not suitable for living creatures, and because of atmospheric drag they're most suited to putting things into lower orbits.

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

"In Project HARP, a 1960s joint United States and Canada defence project, a U.S. Navy 410 mm (16 in) 100 caliber gun was used to fire a 180 kg (400 lb) projectile at 3,600 m/s (12,960 km/h; 8,050 mph), reaching an apogee of 180 km (110 mi), hence performing a suborbital spaceflight."

They'd be great for the Moon though.

Makes me think of "The Moon Is a Harsh Mistress", where the moon went to war with earth by catapulting rocks.

A military moon base could lay waste to any area on earth that way. There will definitely be a new moon race once a permanent moon base becomes sustainable. I don't see how the existing space treaties can survive past that point.

https://thespacebucket.com/what-happened-to-spinlaunch-its-p...

I remember this being a horrible idea for many reasons.

One reason being the speed needed at the start which probably meant most loads burning up in the thick atmosphere immediately.

Another reason being that if you would use it to start a rocket which will only use the spin launch as a booster replacement, you would run into the problem of the fuel being pressed towards the front of the rocket as it is constantly decelerating after the launch. So you would probably need a system to actively move the fuel down to the nozzle.

The Excalibur 155mm artillery shell is supposedly subject to twice as much acceleration as the spin launcher, and it has a solid rocket motor. So it's probably possible. But solid rocket motors are less efficient than liquid fuel.

Maybe a small solid booster to keep it accelerating immediately after launch before the liquid fuel kicks in.

As I said here a few years ago, I support this sort of company. VCs are basically stupid, especially for companies that are more complicated than gluing javascript together, and so it’s only just and right that some actual engineers have some fun in the desert for a few years at their expense, and get some experience putting ambitious, if ultimately silly, machines and prototypes together quickly and scrappily for a few years. Then when spinlaunch goes bust, which of course it will as its idea makes zero sense from an engineering pov, there will be a bunch of hardened and experienced engineers who can go and work for people with more of a clue and do something useful. It’s like a well funded extra-curricular student project.

Accelerating in a huge vacuum chamber seems pretty difficult to achieve, and wouldn't there be a huge shock to the vehicle as it hits a wall of dense air?

How much of a difference would a low pressure chamber make, I wonder? Maybe you could build the circular accelerator then a much longer exit pipe that runs up the side of a mountain. Although that sounds way, way easier said than done! But if your exit air pressure is roughly equal to your accelerator air pressure, then you don't need a fancy airlock system.

The tether they proposed also seems a bit too much of the wishful thinking like "we just need a bundle of carbon nanotubes 1km long!" Wouldn't an electromagnetic accelerator work better?

Well actually....

Even if you place the exit at higher altitude with lower pressure, without a seal you'll still end up with higher pressure at the base. Just like you do in open air, the weight of the air column pushing down increases the pressure.

Good point!

If the launch vehicle can accelerate well enough in low pressure instead of vacuum then maybe you could "just in time" depressurize segments of the tube. Although that's still getting perilously close to the magical airlock concept.

Apologies for rambling, this is fascinating.

It's an interesting idea, but I don't see a feasible use for it on Earth, probably be quite handy for returning bulk materials to Earth from a hypothetical moon base. Unfortunately Earth's atmosphere makes most surface base accelerators to space impractical.

A many kilometers long linear accelerator that ramps off a suitable mountain could make for a interesting 1st stage that wouldn't subject the payload to ridiculous G forces. But you'd still need to accelerate the payload and 2nd stage and with SpaceX and co driving down 1st stage costs I still don't see it as cost effective.

Metaculus has this at 4% that it will launch anything to low earth orbit by 2032.

https://www.metaculus.com/questions/12245/spinlaunch-payload...

According to The Space Bucket youtube channel, there has been no update to the company's progress since 2022, and there was a shake up in the top leadership. It looks like this project is likely dead in the water.

https://youtu.be/kGxmCvLb9bs

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.

⬆ this

The recent news items about them have the "someone please buy us" desperation vibe to them. It was an exciting startup 10 years ago or so, then everything went quiet, then all of the sudden there were some items in the news but nothing really substantial - "we hit orbit" or something like that. Just a nebulous "Oh, there Spinlaunch, remember us?"

There 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.

So, we're back to the space elevator as the only means to prevent burning a bunch of shit for every launch?

Personally, I'd abandone 99% of all launches anyway. We just don't really need 12 different competing 15,000 satelite clusters to start with...

Reminds me a bit of the launch system in When Worlds Collide (1951). (A giant roller coaster track, essentially.)

https://www.youtube.com/watch?v=avtQ8elxL-o

I could imagine commercials, in movies they have this bow and arrow guy the arrow shoots towards the viewer then the logo appears

Here it's a baseball pitcher or that spinning throw (not discuss, they use a ball) then it says "Spin Launch"

Guess we’re gonna have to build our next generation of spacecraft with an inch of milled solid titanium, just like we build our deep sea submarines

> just like we build our deep sea submarines

Nah, I'm sure some expired carbon fibre will do fine.

Related. Others?

SpinLaunch: Giant catapult launching satellites - https://news.ycombinator.com/item?id=41925019 - Oct 2024 (53 comments)

Company wants to 'throw' rockets into low orbit to save fuel - https://news.ycombinator.com/item?id=41768182 - Oct 2024 (3 comments)

Giant catapult defies gravity by launching satellites into orbit - https://news.ycombinator.com/item?id=41919846 - Oct 2024 (3 comments)

Rocket company develops catapult to launch satellites into space - https://news.ycombinator.com/item?id=40731585 - June 2024 (2 comments)

Will physics prevent SpinLaunch from succeeding? - https://news.ycombinator.com/item?id=33687266 - Nov 2022 (1 comment)

SpinLaunch just catapulted a NASA payload into the sky for the first time - https://news.ycombinator.com/item?id=33112413 - Oct 2022 (10 comments)

NASA Tests Gigantic Slingshot for Hurling Objects into Space - https://news.ycombinator.com/item?id=33088860 - Oct 2022 (6 comments)

Can We Throw Satellites to Space? – SpinLaunch - https://news.ycombinator.com/item?id=32375464 - Aug 2022 (5 comments)

An Inside Look: SpinLaunch Flight Test #7 - https://news.ycombinator.com/item?id=31098021 - April 2022 (4 comments)

NASA will test SpinLaunch's ability to fling satellites into orbit - https://news.ycombinator.com/item?id=30996665 - April 2022 (200 comments)

Alternative rocket builder SpinLaunch completes first test flight - https://news.ycombinator.com/item?id=29658592 - Dec 2021 (1 comment)

Spinlaunch: Busted - https://news.ycombinator.com/item?id=29578792 - Dec 2021 (1 comment)

Scientists find a way to ‘catapult’ rockets into space like ‘slingshots’ - https://news.ycombinator.com/item?id=29432727 - Dec 2021 (50 comments)

SpinLaunch completes first test flight with rocket-flinging launch system - https://news.ycombinator.com/item?id=29198589 - Nov 2021 (219 comments)

Spinlaunch with Basic Physics [pdf] - https://news.ycombinator.com/item?id=29183158 - Nov 2021 (2 comments)

Spinlaunch completes suborbital launch without engine - https://news.ycombinator.com/item?id=29175912 - Nov 2021 (6 comments)

SpinLaunch is building a centrifuge to launch satellites into orbit - https://news.ycombinator.com/item?id=25204660 - Nov 2020 (143 comments)

SpinLaunch raises $40M to build a machine to catapult objects into space - https://news.ycombinator.com/item?id=17317688 - June 2018 (105 comments)

Space catapult startup SpinLaunch comes out of stealth - https://news.ycombinator.com/item?id=16439835 - Feb 2018 (110 comments)

Much as I might like to see alternate ways of launching succeed, I have always thought that physics was not on their side.

I have so many questions..! (And maybe the answers are somewhere on the page, but its navigational paradigm is too atrocious for me to handle)

- how fast do you have to push something through the atmosphere to have it reach space?

- and, how fast is the lever spinning to reach that velocity? how precise do you have to time the release?

- after release, your lever is going to be pretty unbalanced. having seen what happens to an unbalanced ultracentrifuge in a lab (spinning a few grams of biological samples), how does this thing launch a 100kg satellite without wrecking the launch station?

- does this mean all the remaining angular momentum is in an opposite weight you discard simultaneously by slamming it into the ground? do you just sling the payload around in some ridiculously unbalanced manner?

- can you launch things with liquids (eg., fuel) at all due to crazy sloshing mechanics?

Okay so say 15.000 km/h, escape velocity + compensate for drag.

At a 100 meter radius, that's a radial velocity of 41 radians per second (4100 meter/second) => 6.5 Hz spinning rate, or one full circle every 0.15 sec

To hit the exit at an angle that's within 1 degree of target, that requires you to launch with 0.15/360=0.4 millisecond precision.

Which seems... not entirely unhinged?

Those 1000s of g-forces though...

You could possibly add a lot of weight on both sides of the spinning wheel, so the lost weight of the payload would not matter as much.

Or maybe put a weight at the opposite end that moves towards the center as you release the payload, compensating for the lost weight at the other end? (* in terms of angular momentum)

Does it though...

Somehow it’s hard to believe that the lower dense part of the atmosphere doesn’t slow it down or even burn it. It happens when these things fall down… why not when going up?

It does slow it down.

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