You can build something like this, but much bigger, and with no external casing, on the Moon or anywhere with little or no atmosphere.
Professor James Longuski and his students at Purdue University have done quite a bit of research on this idea over the years. They call it a tether sling. To keep the tip acceleration (v^2)/r low, you want a large r. Some papers:
If you were on the moon you would only need to match spinlaunch's launch velocity of 8000 km/h and you wouldn't even need rocket fuel. You would only need a $200 battery and a $200 solar panel to fling 1 kg into space every hour of the day, assuming 100% efficiency.
I was quite surprised to discover how cheap it is to fling chunks of the moon into space. I mean... I'm not sure why you'd bother, but still, it interested me.
(My working: 2380 m/s escape velocity, 0.5 * 2380^2 energy in Joules required, convert to kWh, googled battery and solar panel costs, totally didn't consider efficiency anywhere)
> I was quite surprised to discover how cheap it is to fling chunks of the moon into space. I mean... I'm not sure why you'd bother, but still, it interested me
Mass drivers are powerful weapons. Haven't you read the classic "The Moon is a Harsh Mistress"?
now you have me imagining some strange field of lunar rock flingers, ejecting mass into space ceaselessly until the sun stops, all for a very motivated PhD student's thesis
How about liquid oxygen and aluminum tanks made from high-temperature electrolysis of regolith? Now you have rocket propellant and parts. 90% of the propellant mass that Starship uses is oxygen. If you could refuel Starship in space this way, it would reduce the number of launches needed from 10 to 1 (well, maybe 2 if the lower-density liquid methane is too bulky for one launch).
Wouldn't something like a rail gun be simpler? Its basically just a maglev train than carriers a spacecraft. Admittedly a large spinning wheel may be simpler to aim than a few hundred meters of track though.
The tricky thing about using a rail gun is that you need to deliver all the power very quickly which is hard and expensive. With this launch system you can spin it up slowly by feeding in energy and then release the projectile once you're up to speed.
The LHC uses electric and magnetic fields to accelerate charged particles to near the speed of light inside a circular vacuum tube.
To picture a tether sling, imagine a lighthouse on the Moon with a giant arm sticking out of its side, and the arm can revolve around the lighthouse like a merry-go-round. The thing to be launched goes at the end of the arm. Just spin up the arm and let go!
For sending civilian payloads into space, it has a very low chance to reach a price point that is competitive with reusable rockets. You either need an absolutely gargantuan centrifuge -> high capital costs - or you need to subject your payload to thousands of Gs. "The payload" is in this scenario must include 1 ton liquid fuel rocket for every 200Kg you want to put into space, or 1 ton solid for every 100Kg.
You have to ensure this "second stage" will never explode inside your centrifuge despite being subjected to orders of magnitude higher loads than the typical rocket. This is possible but very expensive, you will need huge structural mass to hold what would appear to be thousands of tons of propelant at 1G. So the mass fraction goes down, the costs of the rocket and centrifuge "spin" out of control, and you provide a paltry orbital capacity of a few tens of Kg and only for specifically engineered satellites that no existing manufacturer knows how to build. A commercial dead end.
For military applications on the other hand, it's close to perfect. You don't need orbital insertion, you can accelerate your payload silently without allowing for detection in the early phase of the attack, your projectile starts at essentially cruise speed and can only be detected by infrared emissions due to atmospheric heating for a few seconds until the launch ablative heatshields are ejected. It's a fantastic first strike weapon.
I think you're dramatically overestimating the difficulty of building the projectiles. It's really not that difficult to build electronics that can withstand the required G forces. Here in the UK we built proximity fused warheads for artillery shells using glass vacuum tubes during WW2.
The HARP program in the 1960s experimented with gun launched Martlet series of rockets. They tested several designs using solid fuelled rockets, but the program was cancelled before the liquid fuelled version was ready for testing.
Not for first strike. First strike is about the ability to destroy or seriously degrade an enemy's ability to retailiate.
With this it's huge, cannot be hidden or moved and the orientation would be obvious from a spy satellite. Any serious enemy would just have systems like this under 24/7 observation and would launch retaliation the moment it was fired, or even looked like it was going to be fired at them.
Couldn't it be hidden underground (or in a mountain/large hill), with something like a ring shaped trench or slit leading to the launch aperture? Basically a big, camouflaged version of WWI/WWII-style concrete coastal gun emplacements.
I'm no expert, but I thought ICBM launches were detected using thermal IR sensors on satellites. There wouldn't be any for this launcher. There would still be a heat signature from the second stage, but it wouldn't need to be anywhere near the launcher itself.
This is good spit balling take, but an bad top comment. I assume on HN if someone says something is for the military it has to be up-voted without thinking?
> specifically engineered satellites that no existing manufacturer knows how to build.
Your consumer phone could be launched fine as is. Most satellites are not different, this is a known problem with a know solution. There is nothing magical here. Electronics are fine.
> It's a fantastic first strike weapon.
No one wants this. North Korea doesn't want this. It means it will get bombed. They want second strike weapons. Obviously all locations this is at will be well know, to test it has to be fired. Rockets you can just put randomly under 200 tents. https://dailyuknews.com/us-news/china-is-spotted-building-a-...
> This is possible but very expensive, you will need huge structural mass to hold what would appear to be thousands of tons of propelant at 1G.
But you are politically happy to test nukes in this when civilians seem scared of propellant blowing up?
This has clear civilian potential. This has limited military potential outside of the crossover with civilian. The economics is questionable, but if it works it'll be a game changer. It's great people are working on this stuff.
> Your consumer phone could be launched fine as is. Most satellites are not different, this is a known problem with a know solution.
Communication sat buses have critical mechanical components: solar panel assemblies, gyros, reaction wheels and momentum sinks, unfoldable antennas, propellant tanks and valves. Earth observation sats have optics so fragile that even applying 1 G perpendicular to the design launch vector will damage them beyond repair, so they can't be mated with the rocket in the horizontal state.
All these can be probably beefed up and redesigned to withstand thousands of Gs, but it's certainly not a solved problem, and there is very little incentive for satellite designers to attempt it.
> But you are politically happy to test nukes in this when civilians seem scared of propellant blowing up?
A mechanical destruction of the warhead will not trigger a nuclear explosion, nuclear weapons are designed for this, it will just contaminate the launch stand. You also need much less conventional fuel if any since you are aiming at suborbital, and this reduces the loads and the damage after an explosion. Military risk tolerance is high, if there is a 10% chance if internal detonation then each facility will get to launch 10 warheads on average, probably more than they will ever have the chance during a real nuclear exchange - considering spinup time.
An explosion inside the commercial orbital launcher will wipe out a large investment and might put the whole company in jeopardy, the energies are significantly higher while the acceptable probability of failure is much lower.
> The test projectile "goes as fast as the orbital system needs, which is many thousands of miles an hour," Yaney told CNBC
This is an evasive statement. The test projectile is nowhere near as fast as their planned orbital system. The challenges scale poorly. Acceleration (and resulting loads during the spin) scales with v^2. Then once you hit the atmosphere, drag and thermal flux increases with speed even faster.
--
Here's John Carmack (who ran his own rocket company once, Armadillo Aerospace) on Spinlaunch.
This is fascinating, but I can’t believe he didn’t really address the elephant in the room (for me anyway). The instant the payload is launched, the launching mechanism will still be rotating at several hundred RPM but will no longer be balanced. I don’t see how it wouldn’t proceed to immediately and spectacularly tear itself apart. So they must have figured out how to rebalance it almost immediately. THAT is what I’d really like to hear about; that seems like the hardest aspect of the whole process.
He mentioned it toward the end, but did not describe the solution. I'm thinking the counterweight on the other end would need to move a very precise distance in effectively zero time.
EDIT: hmm, or a supplemental weight on the payload side, moving outward the right distance as the payload releases.
It seems like you'd generally want the non-payload rotating bits to vastly outmass the payload, so its release perturbs the whole system to the least amount possible. And then you use regenerative braking to reclaim the energy .
You got me curious, so I dug up their patent. This is as close as they come to addressing it.
> Although not shown in the previous figures, the circular mass accelerator structure 150 may comprise a second exit port directly opposite the exit port 115 to capture the counterweight 135 that is released simultaneously with the launch vehicle 105 to minimize an imbalance on the motor at the time of release. The counterweight 135 may be a solid material, or a liquid such as water.
The use of a liquid is a curious idea. Perhaps it could be dispersed in such a way as to spread the force of the counter weight being released across a wide surface area? Like a small explosive forces the liquid out in all directions?
Yeah, I didn't see any explanation for that either. With that much kinetic energy around I wonder if it's designed to simultaneously launch a portion of the counterweight.
It's got a lower lever so the overall momentum might be low enough to make that recoverable. Maybe if it's 10% of the rocket's momentum, going into... yeah, it's hard to imagine that being recoverable but maybe it's just weights and that's good enough.
I was guessing, its water in a container with bomb bay like doors, when the payload is released the doors open and the water goes into some complex structure that takes the energy out of the water. but only a guess.
Build the thing on a sea platform. Launch the counterweight into water. Make it sharp-nosed like the payload, so it could potentially survive impact with water and be recovered.
This is either total scam or the founder didn't do school physiscs. Most of the info is quoted as "founder said to CNBC", hence I see no material proof.
A school-level physics calculation is enough to debunk it in a minute.
Earth orbital velocity is roughly 8000 m/s. To achieve even a small fraction of it by spinning, the projectile and the device must withstand centrifugal acceleration:
a = V ^ 2 / r
Let's assume we obtain 1/8th of the orbital velocity, which will give a significant fuel reduction, thanks to fuel is exponential to delta V.
r of the full-scale should be 136 m (small-scale diameter is 91 m as in the article, scaled by 3 as said there too, divided by 2)
1000 ^ 2 / 136 = 7352 m/s^2 = 750 g.
I leave to the others to calculate how many RPMs should the device make. There's no material that can withstand such forces for extention. Many projects of energy conservation with flywheel were cancelled because sighnificantly heavy and large flywheels (couple of tons and just about 1 meter in radius) tear themselves apart at 2-3K RPM.
I've not heard of any devices handling 100g over any significantly long periods of time.
Have you considered it might be you that's lacking in knowledge rather than the investors and founders? You seem quick to call people out on being scammers for something you clearly don't fully understand. Yes you can cite high school math but than you start making assumptions/assertions, drawing conclusions, etc. that are clearly wrong/baseless. Very sloppy arguing.
You, "leave to the others to calculate how many RPMs should the device make"; like the people behind this company that clearly did that math, build a device and then proceeded to launch an object several tens of thousands of feet up. Clearly their math is better than yours.
"I've not heard of any devices handling 100g over any significantly long periods of time."
Show me a complex mechanical device, like a rocket, with fuel tanks, fuel pumps and ball bearings, that withstands >100g continuously for >10 seconds. Turbine blade that has 100g at its tip, is not one.
"Don't learn physics, and you'll live in the world of wonders!"
IDK if they can make it work on Earth, but the Moon would still be valuable - and with zero atmosphere to slow things down.
Production of chemical fuel on Moon is going be tricky, there are no fossil fuel deposits there and water is much scarcer than on Earth. Our contemporary chemistry isn't completely ready for such conditions, at least not on industrial scales.
If we could use a mechanical / electrical mechanism to throw things onto the Lunar orbit, it might be much more efficient than, say, making methane in situ using Sabatier reaction. Solar panels are much more productive on the Moon than on Earth.
Back in 2012, before seeing Kerbal Space Program, I thought of it too. Well, if we build a tower 1 km tall (or find a suitable mountain), have two bobines with 5-10 km cable rotating and gradually increasing the radius while keeping the weight above the ground, then it could launch the vehicle at reasonable g's and within reasonable radius. But still the centrifugal force formula is cruel, and the size of the device is huge.
Regarding cold gas, I found this analysis [1], that essentially says that within 40% of vehicle mass will get you to 500-1000 m/s, dV growing as square root. So it won't make it into lunar orbit.
Makes me wonder about the military uses of such tech. Remember Gerald Bull and his quest to launch a satellite with an artillery piece? He later was embroiled in a project for Iraq to create a supergun that could potentially provide ICBM tech to a country without rocket tech.
I don't see how this is viable as an earth launch system. You have all this complexity and payload restrictions, just to go from a two stage launch system to... a two stage launch system.
However, I think this technology will be extremely valuable for launching material from the moon.
So kudos for investing for this. And I think it will even end up being a profitable investment. Just not for the intended purpose.
I wonder how much lower the g forces would come than from 10k if the radius was larger. The high energy particle accelerator at cern comes to mind. It wouldn't need to be vertical either just at a slight tilt since to go to orbit you need to travel horizontally most of the time.
I'm having trouble understanding how practical this could be. Do you know what tests they've done to find out what kinds of things can survive the extreme acceleration? Do you know what the force from impacting the atmosphere upon leaving the spin chamber is?
I don't think the advantages outweigh the disadvantages.
G-loading. Rockets are normally rated for force in one direction (down) the same as gravity and launch acceleration. They can only handle a few small percentages of G laterally. This rocket would need that, plus at least a few G of lateral acceleration for spinup and a massive negative G capability for the impact with the lower atmosphere immediately after launch.
Was there a G-meter on this rocket/dart? What did it feel like to go from thousands of mph in a vacuum to suddenly thousands of mph at sea level? 50g? It would be like slamming through concrete. Larger rockets would no doubt feel less of this impact but they would still need structures akin to fighter jets. Those structures would be heavy and likely nullify any fuel savings.
Aren't the 10,000 G the lateral force at max rotational speed? I don't think that the transition from vacuum to sea-level pressured air would result in a 10,000 G de-acceleration. But it really must be a non-neglectible impact-like effect.
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Professor James Longuski and his students at Purdue University have done quite a bit of research on this idea over the years. They call it a tether sling. To keep the tip acceleration (v^2)/r low, you want a large r. Some papers:
https://scholar.google.com/scholar?hl=en&as_sdt=0%2C5&q=long...
Note 1: Professor Longuski was my PhD advisor, but I never did any research on tether slings myself.
Note 2: Others have also researched tether slings. The papers linked above give many citations to related research.
I was quite surprised to discover how cheap it is to fling chunks of the moon into space. I mean... I'm not sure why you'd bother, but still, it interested me.
(My working: 2380 m/s escape velocity, 0.5 * 2380^2 energy in Joules required, convert to kWh, googled battery and solar panel costs, totally didn't consider efficiency anywhere)
Hmm. The Moon Is a Harsh Mistress builds a compelling case to do so.
It is easier to send something to low Earth orbit from the Moon than from Earth.
Mass drivers are powerful weapons. Haven't you read the classic "The Moon is a Harsh Mistress"?
Raw material for space station construction.
Deleted Comment
To picture a tether sling, imagine a lighthouse on the Moon with a giant arm sticking out of its side, and the arm can revolve around the lighthouse like a merry-go-round. The thing to be launched goes at the end of the arm. Just spin up the arm and let go!
For sending civilian payloads into space, it has a very low chance to reach a price point that is competitive with reusable rockets. You either need an absolutely gargantuan centrifuge -> high capital costs - or you need to subject your payload to thousands of Gs. "The payload" is in this scenario must include 1 ton liquid fuel rocket for every 200Kg you want to put into space, or 1 ton solid for every 100Kg.
You have to ensure this "second stage" will never explode inside your centrifuge despite being subjected to orders of magnitude higher loads than the typical rocket. This is possible but very expensive, you will need huge structural mass to hold what would appear to be thousands of tons of propelant at 1G. So the mass fraction goes down, the costs of the rocket and centrifuge "spin" out of control, and you provide a paltry orbital capacity of a few tens of Kg and only for specifically engineered satellites that no existing manufacturer knows how to build. A commercial dead end.
For military applications on the other hand, it's close to perfect. You don't need orbital insertion, you can accelerate your payload silently without allowing for detection in the early phase of the attack, your projectile starts at essentially cruise speed and can only be detected by infrared emissions due to atmospheric heating for a few seconds until the launch ablative heatshields are ejected. It's a fantastic first strike weapon.
The HARP program in the 1960s experimented with gun launched Martlet series of rockets. They tested several designs using solid fuelled rockets, but the program was cancelled before the liquid fuelled version was ready for testing.
With this it's huge, cannot be hidden or moved and the orientation would be obvious from a spy satellite. Any serious enemy would just have systems like this under 24/7 observation and would launch retaliation the moment it was fired, or even looked like it was going to be fired at them.
Other applications perhaps.
I'm no expert, but I thought ICBM launches were detected using thermal IR sensors on satellites. There wouldn't be any for this launcher. There would still be a heat signature from the second stage, but it wouldn't need to be anywhere near the launcher itself.
Starship can deliver a payload of 150 tons to Orbit, fully reusable.
SpinLaunch needs a non-reusable second state and can deliver at best a few 100kg.
So what do you think is cheaper, launch 1 Starship or 500+ SpinLaunch non-reusable rockets?
This is good spit balling take, but an bad top comment. I assume on HN if someone says something is for the military it has to be up-voted without thinking?
> specifically engineered satellites that no existing manufacturer knows how to build.
Your consumer phone could be launched fine as is. Most satellites are not different, this is a known problem with a know solution. There is nothing magical here. Electronics are fine.
> It's a fantastic first strike weapon.
No one wants this. North Korea doesn't want this. It means it will get bombed. They want second strike weapons. Obviously all locations this is at will be well know, to test it has to be fired. Rockets you can just put randomly under 200 tents. https://dailyuknews.com/us-news/china-is-spotted-building-a-...
> This is possible but very expensive, you will need huge structural mass to hold what would appear to be thousands of tons of propelant at 1G.
But you are politically happy to test nukes in this when civilians seem scared of propellant blowing up?
This has clear civilian potential. This has limited military potential outside of the crossover with civilian. The economics is questionable, but if it works it'll be a game changer. It's great people are working on this stuff.
Communication sat buses have critical mechanical components: solar panel assemblies, gyros, reaction wheels and momentum sinks, unfoldable antennas, propellant tanks and valves. Earth observation sats have optics so fragile that even applying 1 G perpendicular to the design launch vector will damage them beyond repair, so they can't be mated with the rocket in the horizontal state.
All these can be probably beefed up and redesigned to withstand thousands of Gs, but it's certainly not a solved problem, and there is very little incentive for satellite designers to attempt it.
> But you are politically happy to test nukes in this when civilians seem scared of propellant blowing up?
A mechanical destruction of the warhead will not trigger a nuclear explosion, nuclear weapons are designed for this, it will just contaminate the launch stand. You also need much less conventional fuel if any since you are aiming at suborbital, and this reduces the loads and the damage after an explosion. Military risk tolerance is high, if there is a 10% chance if internal detonation then each facility will get to launch 10 warheads on average, probably more than they will ever have the chance during a real nuclear exchange - considering spinup time.
An explosion inside the commercial orbital launcher will wipe out a large investment and might put the whole company in jeopardy, the energies are significantly higher while the acceptable probability of failure is much lower.
> The test projectile "goes as fast as the orbital system needs, which is many thousands of miles an hour," Yaney told CNBC
This is an evasive statement. The test projectile is nowhere near as fast as their planned orbital system. The challenges scale poorly. Acceleration (and resulting loads during the spin) scales with v^2. Then once you hit the atmosphere, drag and thermal flux increases with speed even faster.
--
Here's John Carmack (who ran his own rocket company once, Armadillo Aerospace) on Spinlaunch.
https://twitter.com/ID_AA_Carmack/status/1458870561606615046
Why so vague?
EDIT: hmm, or a supplemental weight on the payload side, moving outward the right distance as the payload releases.
It seems like you'd generally want the non-payload rotating bits to vastly outmass the payload, so its release perturbs the whole system to the least amount possible. And then you use regenerative braking to reclaim the energy .
> Although not shown in the previous figures, the circular mass accelerator structure 150 may comprise a second exit port directly opposite the exit port 115 to capture the counterweight 135 that is released simultaneously with the launch vehicle 105 to minimize an imbalance on the motor at the time of release. The counterweight 135 may be a solid material, or a liquid such as water.
The use of a liquid is a curious idea. Perhaps it could be dispersed in such a way as to spread the force of the counter weight being released across a wide surface area? Like a small explosive forces the liquid out in all directions?
https://patents.google.com/patent/US10202210B2/en
It's got a lower lever so the overall momentum might be low enough to make that recoverable. Maybe if it's 10% of the rocket's momentum, going into... yeah, it's hard to imagine that being recoverable but maybe it's just weights and that's good enough.
I'd love to see a real explanation.
A school-level physics calculation is enough to debunk it in a minute.
Earth orbital velocity is roughly 8000 m/s. To achieve even a small fraction of it by spinning, the projectile and the device must withstand centrifugal acceleration:
a = V ^ 2 / r
Let's assume we obtain 1/8th of the orbital velocity, which will give a significant fuel reduction, thanks to fuel is exponential to delta V.
r of the full-scale should be 136 m (small-scale diameter is 91 m as in the article, scaled by 3 as said there too, divided by 2)
1000 ^ 2 / 136 = 7352 m/s^2 = 750 g.
I leave to the others to calculate how many RPMs should the device make. There's no material that can withstand such forces for extention. Many projects of energy conservation with flywheel were cancelled because sighnificantly heavy and large flywheels (couple of tons and just about 1 meter in radius) tear themselves apart at 2-3K RPM.
I've not heard of any devices handling 100g over any significantly long periods of time.
You, "leave to the others to calculate how many RPMs should the device make"; like the people behind this company that clearly did that math, build a device and then proceeded to launch an object several tens of thousands of feet up. Clearly their math is better than yours.
"I've not heard of any devices handling 100g over any significantly long periods of time."
You just did.
Show me a complex mechanical device, like a rocket, with fuel tanks, fuel pumps and ball bearings, that withstands >100g continuously for >10 seconds. Turbine blade that has 100g at its tip, is not one.
"Don't learn physics, and you'll live in the world of wonders!"
Artillery shells, even the fancy ones with guidance hardware, can handle such loads too, in compression.
Production of chemical fuel on Moon is going be tricky, there are no fossil fuel deposits there and water is much scarcer than on Earth. Our contemporary chemistry isn't completely ready for such conditions, at least not on industrial scales.
If we could use a mechanical / electrical mechanism to throw things onto the Lunar orbit, it might be much more efficient than, say, making methane in situ using Sabatier reaction. Solar panels are much more productive on the Moon than on Earth.
Actually, I wonder if cold gas thruster can do the same job. (https://en.wikipedia.org/wiki/Cold_gas_thruster) At least some gases are extractable on the Moon surface.
[1] https://digitalcommons.usu.edu/cgi/viewcontent.cgi?filename=...
Did we need to orbit fluidized electronics?
https://en.wikipedia.org/wiki/Supergun_affair
have seen it described as the "canadian iraqi space gun", which causes some people to do a double take
[1] https://en.wikipedia.org/wiki/The_Fist_of_God
However, I think this technology will be extremely valuable for launching material from the moon.
So kudos for investing for this. And I think it will even end up being a profitable investment. Just not for the intended purpose.
G-loading. Rockets are normally rated for force in one direction (down) the same as gravity and launch acceleration. They can only handle a few small percentages of G laterally. This rocket would need that, plus at least a few G of lateral acceleration for spinup and a massive negative G capability for the impact with the lower atmosphere immediately after launch.
Was there a G-meter on this rocket/dart? What did it feel like to go from thousands of mph in a vacuum to suddenly thousands of mph at sea level? 50g? It would be like slamming through concrete. Larger rockets would no doubt feel less of this impact but they would still need structures akin to fighter jets. Those structures would be heavy and likely nullify any fuel savings.