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"?
If your goal is a weapon system, there are far, far better options. Like rods from god and orbital nuke launchers, it just has too many limitations to be practical.
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).
I would be very carefull with any climate intervention where there is no easy way to adjust the effect. Preferably whatever we do should be part of a designed-in feedback loop to stabilize the climate.
You wouldn’t bash in a window at work if the office is too hot. It is super easy to see that that is a hard to undo intervention you might regret later. The climate of a whole planet is much more complex than that, much less well understood and we only have one. Be suspicious of any plan which doesn’t have “knobs” we can adjust as we learn more.
Also we now maybe have the tech to make moon trebuches to fling dirt to shade our planet. Do we have the tech to clean it up too if it blows back in our face? Will we always have the tech? Civilization is not a straight linear progression. Even if we could do the adjustment now who knows maybe thousands of years from now humanity won’t be able to do the same. So it is better if we design our interventions such that they are making the climate stable even without continous tweeking by a technologically advanced civilization. I don’t know how this would be possible without properly designed feedback loops. And I don’t know what feedback system a dust cloud could have.
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!
I am no scientist, I just used to play in playground as a kid and watched allot of figure skating.
When something is rotating as you said, their mass is away from the rotation point, you can increase the rotation speed by moving the mass closer to the rotation point.
When the skater spins with their hands open they gain rotation speed by just gather their hand around the body.
When the kids spin on the round game, they get closer to the center to gain speed and away to slow down.
Is this a thing? Does this actually translates to increased centripetal force? Why they didnt get more speed by using this method?
In principle this would work. If they had a spinning mass, then moved the mass closer to the center of rotation, its speed would increase. The reason they do not do this is that it is just not that useful in this context.
One of the major limitatinos of the SpinLaunch approach is the g-forces. As it is, objects launched by SpinLaunch experience a g-force on the order of 10,000G. For a constant velocity, this force goes up as the inverse of the radius. As a result, you want the mass to be as far away from the center as possible so that the g-force experienced is minimal.
The other problem is that this approach is not actually an efficient way of gaining speed. Conservation of energy is still a thing. The rotating mass experiences an apparent centrifugal force pushing it away from the center of rotation (the 10,000Gs that I mentioned above). In order to move move the mass closer to the center, you must counteract this apparent force. At that point, you are likely better off taking the energy you would spend pulling the mass towards the center and simply apply it directly towards increasing the rotational speed.
> In principle this would work. If they had a spinning mass, then moved the mass closer to the center of rotation, its speed would increase.
Actually it wouldn't speed up. The speed of the mass traveling on it's circular path around the center remains the same. The orbit just becomes smaller and thus the path becomes shorter. The mass now makes more rounds in the same time. It is thus spinning faster around the center but traveling at the same speed on its path around it.
It is a common and understandable error to assume that the linear velocity should remain constant.
If the object goes in a circle, the radial force always acts perpendicular to the direction of motion, and cannot change the linear velocity of the object. The centripetal force does not do any work, the energy of the rotating body remains fixed.
But there is a subtle difference when one does pull the object closer to the axis. First, it is easy to notice that one does expend work. This energy must go somewhere, and there is nowhere else for it to go except into the kinetic energy of the moving object.
But how exactly is this energy transferred? If you think about it, when the object is pulled in, it no longer goes in a circle, but follows a spiral. Its velocity is no longer strictly perpendicular to the direction of the force. If you integrate this seemingly small effect, this is precisely what makes pulling on the sting to increase the velocity of the object.
Ignoring the mechanism, a formal calculation, from conservation of angular momentum or conservation of energy would immediately tell how much the linear velocity of the object would increase when it is pulled closer to the axis.
Sorry I meant for a solution that would work on earth. Couldn't we use magnets to accelerate the ship like a maglev train inside a version of LHC with wider tubes?
IIRC, Alastair Reynolds describes something very much like this in his novel Blue Remembered Earth, which is set on a future Earth about 140 years from now.
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.
Yes, my argument was that, because the second stage would be mechanically so hard to build, driving the cost of the whole installation up, it's unlikely they can offer launch services at a price point low enough to make satellite customers and manufacturers willing to invest in high-G satellites.
I will change my mind when they offer payload to orbit at a price no more than half of what SpaceX can do. Currently, they launch 51 Starlink satellites of 260Kg at a price point of $50 milion, or about $4000/Kg.
Any competitor looking to deploy a high-G constellation will need much better prices, less than $500K per 260Kg satellite, and Starship is on course to slash another zero from that.
They already have a design, so it seems like at least they think they have the engineering problems figured out. This test rig should allow them to verify that.
They might well be able to compete based on differentiating factors other than cost, such as availability. Small sats riding on an F9 are generally on ride-share programs and can have to wait years for a slot. Unless you're commissioning a whole F9, you take what you can get. With this thing they can throw up a single small satellite whenever you like, and pretty much as many or as few as you like.
Price may well be comparable to reusable F9, after all this thing puts the "upper stage" to about the same altitude as an F9 second stage, and as with this the F9 second stage isn't reusable. Also the "first stage" of this thing is a catapult that's functionally infinitely reusable, whereas F9 first stages have only racked up a maximum of 10 launches so far. This catapult should theoretically manage thousands of launches.
Starship is a real game changer for sure, but we'll have to see how that pans out. It's still a long way from being a functioning service doing daily launches.
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.
I believe the parent is right, you couldn't hide it. Even if you succeed in building them completely stealthy, it's just a matter of time until the enemy finds out the locations using espionage or signals intelligence, and after that they will place the site unde non-stop satellite surveillance. They are massive and can't be moved, so they are sitting ducks.
As for launching, you are guaranteed to produce a thermal signature in the first few seconds of flight, since you hit the high density atmosphere at a 3-5 Km/s speed. You will leave a distinct, large and highly detectable infrared signature and the enemy will be alerted: https://youtu.be/JAczd3mt3X0?t=274
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 .
I wonder why they don't just have an inert concrete mass on the other side and an exit port that opens into a sand bunker, sure it's a lot of energy but they don't have to contain it, only limit back splash from the mass hitting the sand. Doesn't even need to be enough sand to stop the mass completely, just enough to catch fragments, the mass can continue into the earth with no consequences
What I came up with was this: the launch arm has a second mass inside it, that will move (via centrifugal force) away from the center, in the same moment the payload is released.
Of course, just having two payloads launch in opposite direction as you propose maybe has much less implementation problems (though I wonder how you stop that second dummy payload in a way that does not cause an earthquake or explosion :)
You could slam a blast door closed behind the exiting projectile. It should be possible to place it in the exit tunnel so that it is fully closed before the inrushing atmosphere gets to it.
Scott Manley talked on youtube about the centrifugal force on the wheel being around 10 thousand g (in the full sized version). So how do you build something that touches a tunnel at hypersonic velocity with many thousand tons of force without disintegrating? It's not like you can just add wheels or skates to your ejected mass (or the tunnel).
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?
Whether liquid or not, running the formula for kinetic energy of the counterweight, I'm getting something around 1 GJ (gigajoule) for a weight of 1 ton at 1500 m/s [1].
According to this site [2] that's equivalent to around 200 kg of TNT. Even with the counterweight being mostly water, that's quite a lot of energy to disperse. How does one evenly spread out the water to a surface the size of a football field? Would that even be enough area to prevent a shock wave being reflected back at the launch equipment?
There's a slide in Manley's video that says gross vehicle weight is 11,000 kg. And 450 RPM @ 100 m diameter, so 2 km/s. Kinetic energy for vehicle is 22 GJ. Equivalents:
* 5 metric tons TNT
* 1/3000 Little Boy atomic bomb
* 4 barrels of crude oil (!)
* Boil 2,300 gallons of water
* 0.25 mg of matter converted to energy
* Enough energy to melt two 11,000 kg iron counterweights, with 2 GJ left over
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.
If you take the simplest design then the second object would be launching into the ground, which is basically what they're doing with the counterweight.
Alternatively you could have a contrarotating system, but I'd then be worried about two high speed objects travelling close together.
The best solution would probably be a metal counterweight, so that you can regeneratively decelerate it from it's exit port.
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!"
It is certainly a good question. The closest I found was the guidance and control system for the HARP project (shooting satellites into orbit). According to Wikipedia: The components of the guidance and control assembly were integrated into a 6.25-inch diameter test projectile. Sun sensors, horizon sensors, telemetry packs, receiving/transmitting antenna, hydraulic systems, logic modules, and gas thruster attitude control systems were all test-fired to approximately 10,000 g'shttps://en.wikipedia.org/wiki/Project_HARP#Martlet_4_Control...
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.
This is probably a silly question, but for the test run, did they launch the rocket straight up? From my limited understanding of gravity, I’d expect it to come straight down if anything went wrong, and it looked like there were quite a few things for it to come down on.
Edit: looking at the video closer, it looks like there is a slight angle to the launch, tilting away from the building next to it, which makes sense.
I think that requirement of “high enough” is why I was surprised, given that a) it was a 1/3 scale model, b) it was a trial run, and c) things frequently go wrong. I guess sitting below it shows their confidence in its ability to get things up there!
Edit: that being said, it does look like there is a slight angle.
You're not throwing the ball high enough in a car that the difference in radius from the center of the Earth makes a difference that you can detect.
For objects above the earth's surface, the radius of the 'orbit' around the center of earth increases, and thus the 'forward' component of the velocity has to increase in order to stay over the same point on the earth. If you shoot something high enough straight up, it will land to the West of the point it was launched from. (This does ignore effects of wind and such, but I believe so did your argument).
It's nothing like throwing a ball up from a running car. Look up the physics of rotating reference frames. I'm sure others can explain it better than I can.
It most likely has a self-destruct sequence. It's basically the same as firing a missile so I wouldn't be surprised if the same type of persuasions were taken as when military drills take place.
I did see that, and that’s what I would expect for the full version (much like launching rockets over the Atlantic from Cape Canaveral). Just a little surprised to see it looking a little more vertical for the trial run.
Cool to see some new ideas here. Saturn V burned nearly 200 tons of propellant by the time it cleared the launch tower. Tsiolkovsky got us to the moon but he won't get us to the stars.
It's enticing because what if you could use this to put fuel and/or parts into orbit to assemble a second stage rocket for interplanetary travel? That'd be sick.
I suppose it partly depends on how high you can reach (LEO?) with this method and whether your spun rocket can carry a fuel payload itself.
The launch mechanism doesn’t have to point straight up; it could point at an angle. Of course that will lengthen the distance traveled through the atmosphere, but maybe it could still work if the launch vehicle can withstand enough heat.
Doesn't matter what angle you throw it. An object in orbit always returns to its starting point. When the object is released, its orbit intersects the ground (unless it reaches escape velocity). If you want to change the orbit so it no longer intersects the ground, you must impart a huge velocity change to the object after it clears the atmosphere, and the only practical way to do that is to include a rocket engine and propellant and avionics in the payload.
That's a very clear argument. Can the effect of air resistance usefully change this, since it's a force acting on the object after it's released? It seems like it's quite bad that the force always points directly opposite the velocity, and I imagine there's a straightforward argument that this can't "improve" the orbit, but I'm not sure offhand how to incorporate that into the analysis.
Air resistance applies a force opposite to the direction of travel (retrograde). At any given instant, the effect is to not change your direction of movement, but decrease your speed of movement. A retrograde force will always lower every point of your orbit (except the exact point where the force was applied, which would remain on your orbit). Since your orbit already has a point that intersects the surface of the planet, your new orbit must also intersect the surface.
One minor complication: Technically, air resistance applies a retrograde force relative to the direction of the wind. At low speeds this might actually increase your orbital velocity. However, the speeds where this is relevant are so small that they are not worth consideration.
I think you might be right, the atmosphere might be able to help you a little. However, any orbit you obtained by interaction with the atmosphere would still intersect the atmosphere, and so would decay rapidly. You'd still need a rocket to boost up afterward. Maybe it could reduce the amount of propellant necessary.
Why not just build couple extra O’Neil cylinders on orbit, run checkouts while populating them over 2-3 generations, and shoot it out? No reasons the majority of interstellar crews has to be Earth born.
Solid rockets had more carrying capacity at one sixth the cost of Saturn 5 at the time. Is the ultimate launch system rated human-safe a combination of spinlaunch, solid rocket boosters to reach highspeed for airbreathing ram/scramjets and lastly transition from airbreathers to liquid propellants?
Just did some quick stubby pencil work, a 2 foot diameter pipe would have to be pumping the propellant at around 70 mph in order to move that much liquid.
Just the lateral deceleration of the liquid slowing down in the tank would probably provide a couple tons of thrust.
People here seem very interested in questions about payload G-forces and basic functioning, but to me, non of those matter. Even if you assume 100% of this works, it has no place in the market.
A Starship can launch 150 tons to Orbit, fully reusable.
Now ask yourself, if SpinLaunch even if you assume the largest possible ground station can not launch more then a few 100kg to Orbit and still requires a Upper Stage rocket that has to be thrown away. How could it possibly be cheaper?
So lets assume an absurdly large SpinLaunch system that can get 500kg to Orbit. You still need 300 launches to match what Starship can do in a single afternoon. In a more practical situation its more like 800 launches to match a single Starship.
Now try to think a gigantic stack of 300 SpinLaunch upper stage rockets that would be thrown away including 300 rocket engines, 300 avonics systems and so on. Compared to a Starship that simply lands and is fully reusable.
Not to mention that a chemical rocket is far more flexible in regards to orbit and far more versatile in possible payloads.
At best it can compete for a very small part of the small rocket launch business. But even then, a lot of the time dedicated launches are used for non-standard orbit and SpinLaunch has far less flexibility then a normal rocket.
If one's spacecraft missed the skyhook on arrival, it could not decelerate and would fly off into space. The thought is terrifying. The film Aniara deals with this scenario. Spacecraft relying on skyhooks for deceleration would need lifeboats that can decelerate and return to the destination after a missed skyhook rendezvous.
I wonder how big it would have to be to even consider putting people on it, albeit sleeping ones. A younger me would look up the required velocity and do the math. A slightly older me is going to sleep soon and will dream that one day he gets to get into the space flinger.
Really big. Escape velocity is 11km/s. Acceleration in a circle is velocity squared divided by radius. Assuming you can withstand 10g with proper gear and drugs that's a radius of a thousand kilometers.
What about putting up something heavier, like a counterweight and a cable? Suppose the radius of the spool is a lot bigger than the launcher, and there's some kind of clutch / synchro to bring it to speed when it engages...
This is a hard part (which sounds impossible to me): since all acceleration needs to be done in a spinner, you need to get to 7900 m/s (even assuming no braking from the atmosphere).
And a = v^2 / r will turn living things into a paste for sane r. :(. I would love to be refuted.
"Braking" will commence immediately after exiting the spinner apparatus though. And commence rather unceremoniously. I don't think this is going to carry humans in the foreseeable future.
Arthur C Clarke proposed the idea in 1950 in a paper, and wrote a rather excellent short story about the concept (and a wild escape from a launch failure) called "Maelstrom II".
In Clarke's story, the launch system is located on the Moon rather than Earth; the lower escape velocity and lack of atmosphere makes the fictional engineering a lot simpler (and allows the climax of the story, which I won't spoil).
When I was younger those devices were called “mass drivers”.
The idea was crude materials would be cut up from moons and asteroids, and launched using maglev rails towards civilization centrals. Or it can also be used for recovery, so long that the landing spacecraft can successfully mate the train.
Above is portrayed first, in cases with Sci-Fi novels, then of course something terrible would occur, and the story starts to ramp up. A shivering refugee is found inside, one of containers suspiciously veer off course, the crucial docking latch breaks, etc.
Perhaps this can also be used to send a continuous stream of supplies, such that we could have a true, inhabitable space station, where all the components required for space travel are manufactured and assembled in orbit.
is this really more efficient than just launching the rocket normally with chemicals?
the article doesn't really go into detail but alludes to the answer to my question being "yes".
I guess the idea is:
you can spin a smaller rocket which requires energy EnergySml. Alternatively you could have a larger rocket which requires EnergyLrg to get out of the atmosphere.
So EnergySml + Fuel in rocket to leave atmosphere << EnergyLrg (which is launch + leave atmosphere)?
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other questions I had were:
- wouldn't the rocket being spun have to be heavier than the equivalently sized chemical rocket because it has to be able to survive being flung around in a centrifuge?
You don't have to lift the fuel. A huge proportion of the fuel in a rocket's first stage is used to lift the fuel in the first stage off the ground for the first few hundred metres of flight. It's almost diabolically inefficient.
Using a really big cannon, not entirely unlike in the Jules Verne novel, has been investigated seriously. It has similar efficiency benefits. Some limits on what can survive the acceleration though: https://en.m.wikipedia.org/wiki/Project_HARP
I knew this would come up in here. Gerard Bull was an amazing character. Unfortunately he was screwed by few governments and at the end he was assassinated (presumably by Mossad).
the important thing I think is that your energy-consuming device (the spinny part) can be huge and heavy and remain on the ground, so it doesn't need to be designed like a rocket first stage. Even if it's actually really inefficient in terms of watt-hours used to spin the thing, doesn't matter.
This is getting pretty close to science fiction. I wonder how much crazier future science fiction writers can get. They're running out of imaginary ideas that hasn't turn out to be real.
So you will only be able to send payloads that can handle such immense G-force pressures, I imagine? Humans can be ruled out then unless you want hominoid scrambled eggs in space
This is quite interesting, recently I watched video explaining similar rail-gun/cannon concept, end explanation what would it take to work for human payload.
What kind of training is there to survive 38G for 0.5s? Maybe the body can become habituated to accelerations over time or something, but what would you be training to actually do before or during those 0.5s?
Not without problems though. He "sustained a fracture of his right wrist during the runs on two separate occasions, also broke ribs, lost fillings from his teeth and bleeding into his retinas that caused temporary vision loss".
This is during short periods (of deceleration), so very different from SpinLaunch's launches.
Physical training I guess, trying different G's for long time, exercising breathing under elevated G's ... I do not know, I just wrote what author said in video.
Thinking about that, would it be possible to "fling" an object trebuchet-style by flying some crazy maneuver with a "hook-plane" instead of a satellite?
That giant sling somehow looks more suited to deliver small packages directly into a backyard than Amazon's attempts at drone delivery.
The military have probably already tried something like that to send ballistic missiles I guess, and in that case you don't even have to accurately aim as the missile can guide itself to the target. Why isn't this a thing already?
In the video of the launch we see the rocket punch through a membrane to go from vacuum pressure to atmosphere, what kind of forces does this involve ? Intuitively it seems like hitting a wall, but thinking more about it, inside the rocket this is just a change of acceleration (jerk) so maybe it's not so bad ? Would a human survive it ?
A human wouldn’t survive the acceleration before it, so I don’t think surviving the punch through matters.
This thing causes 10000 G for a sustained time on the projectile. To put this into perspective above 14 G even fit and trained individuals tend to black out. Blood centrifuges use 1500-3000G for 5 to 10 minutes to separate your blood plasma from the red blood cells. After hours of 10000 G acceleration a human body will be a red goo stratified into density layers at the wall of the vessel.
Punching through a membrane won’t faze the goo much comparatively.
What if they built a giant multiple mile long electromagnetic rail gun that accelerated the payload to a few thousand miles and hour and fired it off into orbit? It would solve the same problem as this spinny thing but would subject the rocket to lower g forces during its launch?
I wonder if this could be used in a rifle type design, where the "spinner" would carry an impactor that would push against the space-bound rocket/projectile, to avoid (some) of the high g-forces?
Yes there would definitely be quite a bit of force at impact time, but the projectile wouldn't have to experience an hour of high g-forces, just a few moments.
How much force is exerted on the rocket / payload when it is released from the vacuum chamber — traveling at full operating speed for an orbital mission — and smacks into the atmosphere?
What’s the reason they have decided to couple this with a two stage chemical rocket? - Would the physics/g-forces reason be too much to go all the way or some other reason?
The goal is orbit, and orbit means going very fast sideways at high altitude, where this launcher can't point (because it's at ground level). So, you can't go "all the way" without putting in sideways thrust to turn your trajectory into proper orbit. Without a rocket to provide that sideways thrust, this launcher will throw things up in a ballistic trajectory, and they'll come back down to Earth with a big crash (given enough sideways velocity, they'll "miss" the Earth and be orbiting).
Compare the SpinLanch rocket specs [1] to Electron in [2].
Payload: 200kg vs 300kg
Height: 6m (est) vs 18m
Wet mass: 11t vs 13t
Stage 1 thrust: 75kN vs 230kN
Stage 2 thrust: 5kN vs 26kN
Engines: Pressure fed vs Electric pump fed
The SpinLaunch rocket dumps its shell before turning on its engines, and presumably has much lower gravity losses, so despite shockingly similar wet masses, the rocket and its engines can be greatly downsized.
I don't have any solid opinion about the concept, but it does seem like “smaller tanks” is maybe not the best description of what is a fairly significant design change. You do shed a lot of complexity from the propulsion systems, but I'm far from sure the stuff you add is any cheaper.
Yeah, that's probably the right take. They are removing a stage though, the implied third stage, but SpaceX is already doing that with better rocket engineering.
From the Scott Manley vid on it, the full scale orbital version is doing 10000g at the tip when it's at full speed. I guess if you didn't want to go as far you could lower that but by the time you're at something tolerable to humans I don't think you'd have much energy to play with. You could try significantly increasing the radius to lower the acceleration but I suspect you'd need to get impractically large before you had something that wouldn't kill people.
That first part is correct; gravity is measured in units of acceleration.
But I have no idea what you mean by "velocity squared". If you mean the ordinary sense, of multiplying something by itself, you're wildly wrong. Acceleration is the derivative of velocity with respect to time, dv/dt, and it is measured in units of velocity over time, not units of velocity squared. Its magnitude is unrelated to the magnitude of velocity.
This video is really weird because usually a launch video that has all the theatrics of a Hollywood production (all white launch room with dramatic lighting and shallow depth of field cinematography) would usually be done by trust-fund startup LARPers, but they actually built this shit and launched it which is not characteristic of a LARPer.
answering "Starship" to this question is the equivalent of being the kid in 5th grade who made a finger gun every time they played rock-paper-scissors and instantly won.
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.