SpinLaunch And The History Of Hurling Stuff Into Space

It’s fair to say that there’s really no phase of spaceflight that could be considered easy. But the case could be made that the most difficult part of a spacecraft’s journey is right at the very beginning, within the first few minutes of flight. At this point the vehicle’s booster rocket will be fighting with all its might against its own immense propellant-laden mass, a battle that it’s been engineered to win by the smallest of margins. Assuming the balance was struck properly and the vehicle makes its way off of the launch pad, it will still need to contend with the thick sea-level atmosphere as it accelerates, a building dynamic pressure that culminates with a point known as “Max q” — the moment where the air density imposes the maximum structural load on the rocket before quickly dropping off as the vehicle continues to ascend and the atmosphere thins.

Air-launched rockets avoid flying through dense sea level air.

While the vast majority of rocket launches have to contend with the realities of flying through the lower atmosphere, there are some exceptions. By launching a rocket from an aircraft, it can avoid having to power itself up from sea level. This allows the rocket to be smaller and lighter, as it doesn’t require as much propellant nor do its engines need to be as powerful.

The downside of this approach however is that even a relatively small rocket needs a very large aircraft to carry it. For example, Virgin Orbit’s LauncherOne rocket must be carried to launch altitude by a Boeing 747-400 airliner in order to place a 500 kg (1,100 lb) payload into orbit.

But what if there was another way? What if you could get all the benefits of starting your rocket from a higher altitude, without the cost and logistical issues involved in carrying it with a massive airplane? It might sound impossible, but the answer is actually quite simple…all you have to do it throw it hard enough.

Getting Revved Up

It might sound like science fiction, but that’s exactly what startup SpinLaunch is currently working on in the New Mexico desert. The plan is to use their mass accelerator, essentially a vacuum-sealed centrifuge, to spin a small rocket up to a velocity of 8,000 km/h (5,000 mph). The vehicle will experience up to 10,000 Gs before it’s carefully released at the precise moment that will allow it to exit the centrifuge skyward through a rapidly-actuating airlock.

The rocket would then coast to an altitude of approximately 61,000 meters (200,000 feet), at which point it would ignite its first stage engine. From that point on the flight would progress more or less like a traditional rocket launch, with the payload ultimately being accelerated to a nominal orbital velocity of  28,200 km/h (17,500 mph). The big difference would be cost, as SpinLaunch estimates each launch could be cost as little as $500,000 USD.

Currently, SpinLaunch is running tests on a one-third scale centrifuge that has a diameter of 33 m (108 ft) and forgoes the complex high-speed airlock for a simple sheet of thin material that the test projectile smashes its way through when released. This naturally means the centrifuge loses its vacuum upon release, but that’s not really an issue this early in the game; maintaining vacuum will only become important when the system is fully operational, and is intended to help maintain a rapid launch cadence as the massive centrifuge chamber won’t need to be repeatedly pumped down.

The operational SpinLaunch rocket won’t be much different from a traditional booster.

So far they have flung passive projectiles to a reported altitude of “tens of thousands of feet”, but that’s a long way from reaching orbit, much less space. The key to making this system work is developing a rocket that can not only withstand the immense g-forces it will undergo while being spun up to speed, but also be able to guide itself during the coast phase before engine ignition using either control surfaces. It should also go without saying that such a rocket only has one chance to get it right — should the engine of a traditional booster rocket fail to light at T-0, the launch can be scrubbed and the vehicle reconfigured to try again. But there’s no do-overs when the vehicle is already flying through the air.

SpinLaunch seems confident they can solve the engineering issues involved, but the fact remains that a similar project was undertaken as a joint venture by the United States and Canada in the 1960s, and things didn’t exactly go to plan.

The Need for Speed

Firing the HARP cannon.

Technically the High Altitude Research Project (HARP) got its start in the 1950s when ballistic engineer Gerald Bull got it into his head that with a large enough cannon you should be able to shoot a payload directly into space. But anyone familiar with Jules Verne’s From the Earth to the Moon knows that the idea is much older than that. Conceptually it makes a certain degree of sense, and it’s not as if humanity hasn’t spent hundreds of years perfecting gunpowder weapons anyway.

The HARP cannon was built by welding together 16-inch naval gun barrels, and mounted in such a way that it could be raised into a near vertical position. Barbados was selected as the primary test site as its relative proximity to the equator theoretically meant projectiles fired eastward would receive a boost to their velocity due to the Earth’s rotation. Starting in 1962, a series of launches were conducted that saw the cannon fire Canadian-made Martlet sounding rockets of roughly 1,800 mm (70 inches) in length.

Early flights carried research payloads that not only studied the performance of the cannon itself, but also observed upper atmosphere and near-space conditions. Updated versions included solid rocket motors that were designed to ignite after the rocket had coasted for about 15 seconds in an effort to increase their velocity and maximum altitude. The ultimate goal was to develop a multi-stage rocket that could carry a small 23 kg (50 lb) payload to an altitude of approximately 425 km (264 mi).

By the time HARP ended in 1967, the cannon had successfully fired more than 200 Martlet rockets, some of which reached an apogee as high as 180 kilometers (112 miles). With a per-launch cost of just $3,000 USD, or roughly $27,000 in 2022, it remains one of the most cost-effective means of delivering a payload above the 100 km Kármán line that marks the internationally recognized boundary of space.

Unfortunately, despite considerable effort, HARP was never able to develop a Martlet rocket that could successfully accelerate itself beyond the initial velocity at which it was fired from the cannon. Because of this, none of the rockets were able to reach orbit, and fell back down to Earth — often not far from the cannon itself.

The primary issue was the inability to develop a rocket engine that could survive the 12,000+ g’s each rocket was subjected to when fired from the cannon. So while HARP was technically a successful space launch program, it was limited to suborbital research flights which became less scientifically valuable as the more traditional rocket programs spearheaded by NASA began to mature.

Exploring New Opportunities

Of course, just because the HARP engineers couldn’t design a rocket engine that could survive high g-forces in the 1960s doesn’t mean SpinLaunch can’t do it. It would hardly be the first time a small startup achieved something the entrenched aerospace industry had deemed to be impossible. The company is also clearly aware of the challenge, as they’ve recently released videos explaining that a large portion of their research right now is going towards exploring the effects of the centrifuge environment on various rocket and spacecraft components.

SpinLaunch has found modern electronics to be surprisingly resilient against extreme g-forces.

But the fact remains that there are many challenges ahead for SpinLaunch. History tells us that the development of the engine won’t come easy, but there’s truly no precedent for building a mass accelerator of the scale that would be required to hurl their vehicle into the upper atmosphere. One also can’t ignore the reality that the cost of spaceflight is already dropping precipitously thanks to commercial competition between providers such as SpaceX, Rocket Lab, and Astra. A launch price of $500,000 would have been revolutionary 20 years ago, but today isn’t far off from where the market is headed anyway.

Spring-loaded CubeSat deployment from the ISS

That said, all signs point to an exciting new era in space exploration ahead, and it’s not outside the realm of possibility that SpinLaunch could find its greatest success away from Earth. For instance, a SpinLaunch accelerator on the Moon would have a far easier time hurling vehicles into orbit without an atmosphere to contend with. Given NASA’s goal to establish a long-term presence on and around the Moon, a system that could cheaply loft payloads from the lunar surface would likely be in high demand.

One could also imagine a small centrifugal satellite launcher mounted to a future space station to dispense CubeSats and other payloads with limited internal propulsion. It might sound far fetched, but keep in mind that the Japanese JEM Small Satellite Orbital Deployer (J-SSOD) currently in use on the International Space Station uses a simple spring-loaded mechanism to push the spacecraft out of their storage racks. A small mass accelerator that allows the spacecraft operator to select the velocity and even departure angle for their craft would be a clear improvement over the current state-of-the-art.

The fact is, we simply don’t know what the future holds for SpinLaunch. Their current technology demonstrator is impressive for what it is, but at the same time, is so far removed from what would actually be required to achieve their goals that it’s hardly an indicator that the company is on the right track. Only time will tell if they can succeed where others have failed, or if their mass accelerator will join HARP as just another interesting footnote in the long history of spaceflight.

156 thoughts on “SpinLaunch And The History Of Hurling Stuff Into Space

  1. I suspect there aren’t many items that we need in space that also can withstand 10,000 G’s. That’s 140,000 pounds per square inch of pressure, far more than a bug experiences when he goes splat across your windshield. Modern electronics won’t, neither will we or anything contained within a tank or anything with any sort of structure. A block of aluminum would but what are you going to do with that in space?

    But the technology could be used as a weapon.

        1. Almost any SMD device will survive both enormous acceleration and enormous jerks (change in acceleration) with the exception of some MEMS components. Modern electronics are far more G-tolerant than many assume.

          1. Other than the glass bonded display techs that lots of people have mastered the art of breaking via a small drop – so with pretty low g loads I’d agree.

          2. Sure, SMD assemblies that are manufactured and hardened properly can survive what they were designed for. But you can’t assume that almost any SMD device will survive… Every component is attached with 2 or more solder joints and every one of those solder joints ha it’s point of failure.

            For example – We used to test PCB assemblies rated for air flight. Someone made a 1 line error in our shaker table program and the surface mount tantalum caps flew off the board we were testing.
            And these weren’t large parts, they were only 10 to 35 microfarad caps. The acceleration sheared both solder joints and the glue dots that were holding the caps to the board. I did the math and that one line error change linear acceleration in one direction from 12 G’s to 120 G’s.

          3. In many cases the whole assembly could be potted in a material like epoxy. The potting material surrounds all components and takes the stress, instead of solder joints taking the stress. Of course, that makes the whole assembly heavier….

      1. Yes but what about the stuff you typically find in satellites?
        Folded solar panels, lightweight main structures, small propulsion systems, antennas, etc…
        Ruggedizing that to survive 10000g instead of the typical 4-8g will quickly eat away the mass budget.

        1. Less so than you would think, while you certainly won’t be launching the most delicate designs this way with the bulk of the launch energy provided from the ground you can get much much heavier payloads without having to carry more fuel to carry the fuel to carry the fuel to carry that extra weight, which allows for much more durable higher mass payloads to take the G loading.

      2. There is a tremendous difference between reaching orbital >altitudespeed<. SpinLaunch can possibly get a rocket-assisted package to minimal orbital altitude.

        But when their package gets to orbital altitude it will be essentially motionless horizontally. It then needs to accelerate to orbital speed of about 17,000 miles per hour.

        SpinLaunch can’t use liquid propellants because the plumbing can’t survive the g-forces. HARP’s solid propellant was extruded aluminum, ammonium perchlorate and Teflon with a Viton binder; it was about as hard as Formica.

        I don’t think SpinLaunch can carry enough propellant to orbital altitude to then achieve orbital speed.

      3. the applications to the sport of baseball ARE LEGION, while these orbs have been fired in the single number mach, the lethality of the game could be greatly increased. To get on base would almost have to be an intentionally struck hitter.

    1. The HARP program *did* successfully launch electronic instrumentation that survived the 12,000 G’s acceleration. The US Navy also has many “smart” artillery shells that contain electronics. So it *is* possible.

      As the photo shows, several rather ordinary electronic items also survived surprising G levels. What do you think the peak G force is when you drop an ordinary integrated circuit on a concrete floor? It’s certainly in the 1000’s of Gs — and yet they survive.

      “Many things are impossible only so long as one does not attempt to do them.” — André Gide

      1. My mother had a Galaxy S8 phone screen crack, despite a tempered glass screen protector. It fell about 2 feet from the arm of her chair and struck its face on the corner of her laptop that was on the floor. Somehow it managed to strike into the tiny gap between the screen protector and the rubber case. Same thing happend to an S8 my sister had. Fell off her lap onto gravel, onto a chunk that had a point upwards and just the right width to go between the glass screen protector and the case.

        Before that, I had an S4 which got knocked out of my hand and of course it fell face down onto a tile floor. Unlike the S8’s mine got the cracked, destroyed the digitizer and the OLED display. Fortunately I had installed Vysor and had it setup with my desktop before that happened, so I was able to copy everything to the SD then wipe the phone.

        1. You maybe astounded to learn, that when a weight or a momentum is arrested by an extremely tiny area, a small point, the pressure on that point can be from hundreds of thousands to millions of PSI.

          Whereas a constant acceleration of 20,000g, would apply the equivalent of mere tens of thousands of PSI evenly spread. For instance, a phone that’s flat, resting on it’s 3×5″ back, may weigh a quarter pound, and thus be exerting 0.0167 PSI on it’s rear surface at rest under earth g. So multiply that by 20 thousand and we get 333 pounds per square inch.

          In other news, a walnut explodes when you hit it with a sledge hammer.

        2. The ‘screen to the edge’ and ‘curved glass’ style is stooopid, only makes the phone more fragile. I could forgive it easily if magnets or screws or something removable was used so the screens were easy to replace. (Off topic: I would gladly trade a half inch of vertical screen for another quarter of an inch width, Note2 is still the best aspect screen I’ve ever had, and Note4 with the IR blaster still the most useful)

          Keep in mind a lot of the phones are compatible with HDMI and USB hubs, for $10-15 you can recover with a computer mouse and TV.

          I like to install an alternative recovery like CWM or TWRP (Clockwork Mod Recovery, or Team Win Recovery Project) on the firmware for this exact reason: hardware or software failure. Its saved my bacon more than once, of course you do need an unlocked bootloader.

          My wife’s (totally usable with debloated stock rom) Galaxy Tab S2 developed a problem with the lock screen, I was able to go in with the recovery and delete the lock screen file. I assume I can password the recovery so it wouldn’t be a security issue. At least Android gives you a wink and a nod, unlike the ‘iPxxxx’ devices that claim they are secure with no way to check you have a spyware infection from a three letter government backed espionage firm

          1. Nope some high concept designer somewhere has decided the ideal handheld formfactor is exemplified by the cable remote, you will have a 8:1 screen and like it.

      2. There was a great Frontline episode about Gerald Bull and his SuperGuns research which unfortunately followed a new path to develop a potentially devastating weapon. He ultimately struck a deal with Saddam Hussein to develop this weapon for Iraq. And if I remember correctly, Bull mysteriously disappeared and later was found murdered in Lebanon. No suspects were ever identified.

        1. Bull was assassinated in his hotel in Brussels, Belgium. The primary suspect is the Israeli Mossad because his supergun was pointed at Israel and he was helping Iraq improve its medium-range ballistic missiles (“SCUD”), also aimed at Israel. Iran also had incentive to kill Bull, but didn’t have the skill or reach of the Mossad.

          1. The Iraqi supergun was a massive scam. There is a section only a couple of miles from me in a museum, the barrel wall thickness is only a couple of cm. It would have burst on first proper firing.

          2. It doesn’t work like a one bang and done gun though. You’re thinking USS Missouri when it is like the German WWII “Millipede” V3 https://en.wikipedia.org/wiki/V-3_cannon

            So you don’t have to have barrel cracking pressure at the bottom to still have enough left that it at least manages to fall out the end. You just keep topping up the pressure as the projectile goes up it.

    2. So, what i am wondering: how is this centrifuge balanced, and what happens to the balance once the payload is ejected?
      Do they launch a counterweight into the earth?
      Or do they just casually spin up an off balance centrifuge up to 10k g?

    3. Aside from potential weapons applications, I think this technology would be better at (admittedly not near future) application like moon/mars/asteroid mining where the reduced gravity and less or absent atmosphere remove hurdles. Additionally, with a chunk or canister of ore they wouldn’t have to worry about g forces.
      That all being said, there are still challenges to overcome before that is even viable.

    1. Access to space will absolutely be required if we are to deal with and make real progress fixing climate change, while keeping a human world remotely similar to todays, and things like this and the massive reuseable rockets are making getting those useful satellites and in the near future quite probably rarer mineral imports from space affordable, and vastly more efficient. Way greener than the previous options.

      If you don’t have space launching capacity say goodbye to anything like reliable weather forecasting, GPS navigation, and global communications (to name a few) in relatively short order – society relies on it and making it massively less expensive and greener to launch these required services which both SpaceX (as you mentioned Elon) and this concept are taking steps in the right direction for ever better results.

      1. All the things you list can be done well enough with current generation of rockets. We don’t need crazy amounts of launch capabilities. Space mining is unrealistic and not necessary. We can cleanly mine minerals here on Earth for less effort than mining them in space.

        1. The current generation of rockets, at least with SpaceX’s falcon 9 now existing and a few of the more promising looking rivial are not bad – but they only got that way from being relics of the cold war very recently thanks to investment mostly for the commercial uses of space by folks with some vision, with your attitude…

          If it wasn’t for them the ‘best’ launch vehicles are very very much obsolete so consuming vastly more, often much more toxic fuels, AND being entirely disposable so vastly more energy wasted in building the launch vehicle… The least green thing you can possible have to provide the services… I can agree we don’t need 8 millions competing LEO internet systems, but that isn’t saving many launches these days..

          Space mining really isn’t unrealistic – once you are out of our gravity well you don’t need much energy to shift around so once there give any huge mass the tiniest of push and it will move, and stay moving, very very damn slowly, but more than enough to deliberately crash mineral rich or artificial processed asteroids into a very precise and location many years later.

          On Earth really isn’t less effort, you still have to fight with gravity moving the spoil which usually amounts to more than 90% of the material moved, the easy way to get at the mineral you actually want is often strip mining, which is about as destructive a process as you can get, mining often contaminates ground and river water and there is only so much of everything on Earth – once you really start to run out of the rarer or most high demand minerals there is no choice but to get them from elsewhere… And if you want to support anything like the current human population you will need a great deal of rarer minerals for all the electronics… (Note not saying mining on Earth can’t be done cleanly, but it commonly isn’t done even remotely cleanly, and even if it is there is still the hard limit on how much x there is)

          1. You’re way wrong on space mining. Asteroids would be easy to place wherever we wanted if they were stationary with respect to the Earth and the rocket and there were no other planets or stars in the solar system
            This is not the case
            Moving a giant asteroid would require a ludicrous amount of fuel

          2. You don’t need to MOVE the Asteroid the whole way at all, just tweak its orbit the tiny bit so it intercepts the orbit you want it to eventually, and it only needs to do that intercept once – its not like you need to get really precisely match orbits for docking, its so much easier to have it crash on purpose. Also who said anything about Giant – even the right tiny asteroid seems likely to be a stupidly high yield source of materials, still going to have really high mass but that doesn’t matter too much as long as its not extinction event high…

            The course calculations are challenging the amount of fuel need not be huge though – if you don’t need the asteroid to arrive yesterday, tomorrow, or next week you can wait for it to come to you with very small changes in its original orbit. (I expect in practice you would either send up a catch rocket for further steering when its getting close or launch your more processed asteroid chunks in something similar to the shuttle to control its entry and mean only the cheap disposable carrier burns up)

            If everything was stationary relative to each other you would actually need way way more fuel – as you can’t just take its existing motion and give it a nudge to eventually pass the destination you want, you would have to effectively start it from zero…

      2. Before GPS there was LORAN. Global positioning, at least on land, doesn’t require satellites. Likewise, global communications can be done with cable and land-based microwave, as most of it already is,

        That said, loss of space access would be a disaster and improving access to space is a tremendous good.

        1. But with how very much, especially in such an environmentally damaged and global economic world we are reliant on shipping we need coverage over oceans, and coverage that won’t be knocked out by a storm (long term or easily anyway).

          And weather predictions are only going to get harder and yet become more relevant – in the last few decades when forecasting got pretty damn good it almost never said anything that important or with improved precision enough to really matter, oh no the picnic got rained on, or the sea is a bit too dangerous to be out on today afterall is about the worse shock you can get as you can see and prep for the by cyclonic storms with or without space, and being such significant forces you prep even when its not expected to pass that close to you.

          But now extreme weather is becoming so common knowing if its going to rain any time in the next month, and how badly is going to start becoming important for water consumption and flood protections, and knowing how much sun and wind will be needed to manage the electrical grid effectively.

          There really isn’t a way to move forward without space access, though I do agree many things we can and do use space for are functionally replaceable, to a useful enough extent anyway, and its not like if we stop launching stuff now space will suddenly empty, there will be many years of degrading utility from the existing networks.

        1. Rather hard to have 5 times more launches, as space in near Earth orbit is already rather congested, throwing ever more stuff up at that rate you wouldn’t actually then be able to keep launching anything at all in very short order with all the stuff already up there in the way.. Maybe you could have 5 times more than today for a year or two, but longer than that no, and by the time this concept is really ready to go SpaceX may already have filled much of Earth’s Orbital space with the starlink and their clients satellites…

          At least until you get on to serious humans living and working in deeper space or at least mineral extraction from the Asteroid belt or something similarly farther out, so there are launches for deep space purposes (though those would be MUCH more expensive so likely kept to a minimum), and that is assuming you can launch such stuff from Earth – which with the cloud of crud in orbit already may be impractical – just send up the high precision hard to make electronics and such in a small supply mission.

    1. IDK if the Spinlaunch CEO is the right guy to do it or not, but this dude here comes across as the kind of towering intellect, who in 1895, you’d have to take hours to explain to that IC propelled carriages were possible because you removed the horses, and that his criticism that it was impossible because you’d run the horses over is nonsense.

      In other words, I think he sets up a bunch of straw men to knock down, and does a lot of appealing to ignorance, aka “I personally cannot conceive of a way around this huge (minor) problem so of course it’s impossible.”

      1. He is really a smug asshole. Every one of his videos is taking some claims that are made and then comparing against some arbitrary test. Like the one in here where they say they have run tests to mach 6 and so he grabs frames from some arbitrary test in a promotional video and for some reason assumes that is the fastest test they’ve ever run?

        I was on a DARPA program that he “busted” to extract water from the air. Spoiler: it definitely works though he insisted it wouldn’t.

          1. Mythbusters was far from perfect, but they showed real actual tests and drew conclusions from it – that is 90% of the way to really, really good science, all its lacking is larger sample sizes, a budget sufficient to improve the scale/quality of the simulations and the academic papers and workings to really make replication of their results or refuting of the method more possible.

            Just yelling stuff will never work, is stupid etc with no actual proof of anything, making sure to only show what they want you to see is about as far from Mythbusters as its possible to get…

        1. The self filling water bottle?

          It might extract water from air (like any bog standard dehumidifier). But the claims it’s promoters make are clearly bullshit and its gofundme backers clearly chumps (who were lucky to get together with their money in the first place).

          1. Later in that video he calls out an Omar Yaghi paper that operates on a totally different principle and basically says this academic paper is also nonviable. These desiccant dehumidifiers definitely work though, whether powered by solar, fossil fuels or batteries, so I have no idea why he dragged that discussion in other than to look smart?

        2. I was on a DARPA program that used cold fusion to produce unlimited free electricity from salt water.
          Spoiler: condensation of water from air is a known problem with known solutions and the ones he has debunked are based on their claims about the amount of energy required for the water collected. He didn’t say you couldn’t do it – he said they lied about the efficiency.

          1. I think you’re selectively listening to him. He specifically called out an Omar Yaghi paper and pointed to test leads connected to the demonstration metal organic framework harvester and suggested they were pumping water in. It was bananas. He thinks a respected academic is just going to fake data for a paper like this? The DARPA solutions just scale up Yaghi’s solution, and they work.

        3. I got about as far as his complaining about the “whoosh” sounds in a vacuum before I gave up. The guy apparently loves to pick irrelevant nits and use those as “reasons.” Total moron.

        4. You provided a link to a very short overview of what this DARPA project wants to achieve – can you provide a link that actually backs up your claim that it actually achieved its goal?

      1. He hates Solar Roadways. And he does tend to be a contrarian, though he does often have some good points, even if he is a bit of a jerk. In fairness, solar roadways probably is a dumb idea. The angle’s not great, roads get really dirty and making a solar panel tough enough to survive in that environment is really difficult (can’t even make normal pavement roads that last all that long). Better to put panels on roofs and over parking lots first. For that matter, putting panels over the roads (like a roof) might be more practical. I’m sure they’ll keep trying though and maybe they’ll figure something out, but I suspect solar roadways will be a technological dead end – there’s just cheaper, easier, better ways to accomplish the task.

        1. That group in particular are clearly scamming gofundme. They haven’t really started trying yet. Just putting on a show.

          However, it remains an immoral and unethical act to let a sucker keep his/her money, so good on the scammers.

          Solar bike trails don’t work (been pilot projected, in some mayo on french fries type eurospot). Solar roads for cars are an _idiotic_ idea. They haven’t even worked in a pedestrian quad.

          Solar roadways should have been discarded as an idea after an hour of thought. Perhaps set for revisit after they were done with roofs, but no, not even then.

      2. At least that would be a defensible position as removed from the engineering realities that make the idea impractical in tests so far it actually makes some sense on paper – a very large surface area you were building and maintaining anyway that connects major electric consumers and is usually empty (on average in many places) – so lots of good sun capture space.

        1. Honestly the idea of large scale solar for transportation would and could work but for trains not automobiles.
          The idea has few requirements as rail is by far one of the most efficient methods of transportation over land and would benefit from electrical input by trackside solar but not to the extent of financially covering the cost of security to avoid having the solar arrays which would be laid for miles next to the rail lines and easily stolen or exploited by locals (a problem india has with it’s standard electrical grid right now) so possible usefulness aside the actual value of solar for transportation is limited right now.

    1. What I would like answered is how the angular momentum is handled at the instant of launch. The images I have seen show the projectile stuck to the end of the arm. So the projectile is spinning end for end at the same RPM as the arm. That spin needs to be removed at release – how?

      1. As soon as it is released there is no force trying to make it do anything but the drag slowing it down – so its not really spinning end over end at all, as that is only happening because of the external force. All it wants to do is fly dead straight off the arm by its own inertia, and its being tethered to the arm that forces it to go round at all.

        If it wants to tumble after release that will be because the COM of the whole thing is wrong or the aerodynamics are and if there is a little residual spin (no system is perfectly going to follow the ideal mathematical models) than the aerodynamics effects should handle it pretty easily, as there is so little of it.

        1. I think the problem there is at the moment of release and for several meters there is no aerodynamics because of the vacuum. It probably sorts itself out a few meters outside, but there needs to be some plan to help it out in the interim. Magnetics maybe.

          1. But even without aerodynamics at that initial stage there shouldn’t be any tumble – as the only reason its circles at all is the constant force of the tether to the arm, release that force and there are no external forces acting on it and its momentum at that point wants to carry it off in a straight line – its not got any stored rotation of its own, you are not giving it any rotation at all relative to itself – as far as its concerned you pushed its nose forward and kept doing it to a great speed and then turned gravity off.

            So the only tumbling that should happen is if the release isn’t clean in some way and during the release it gets given a bump that will make it rotate around its COM, or its got a very sloshy payload that when the ‘gravity’ is released could cause similar trouble, and in both cases with the rather stupendous launch velocities involved it will be in the atmosphere and get stabilized by the drag far too fast to actually tumble even if you tried to make it tumble I would think – how far can it possibly start tumbling before being out in the thick low altiude air when being launched at that sort of speed, I think you would have to actively get it spinning around its COM on the arm before launch to even get 1 revolution before even the slightest of stretched sphere level of aerodynamic stability catches it.

          2. Hmm will point out that they are actually planning on using a much smaller rotor than I thought (don’t know how I missed that in the article), so it will matter a little more than I was thinking, though does make the system rather more portable. But still the launch velocity is so high its into the atmosphere so damn fast I can’t see it mattering.

          1. We are talking about a system that becomes almost instantly an aerodynamic system, as soon as you take that constraining force making it circle away and give it a good thick atmosphere the angular momentum is easily lost, as you are not deliberately are trying to make it tumble!

            Its effectively a rounding error level, at least when you have an atmosphere to easily take it away – would make a big difference to the space launch concepts though, as you would then actually have to actively do something to counter it…

            But when you are cutting through a good thick atmosphere at very high speed fractions of a second after release it really doesn’t matter.

          2. Love this question.

            The earth is spinning about its own axis and about the sun.

            The spin about its axis has electrical forces holding it together; otherwise the earth would fly apart in a donut like explosion.

            The spin about the sun is held by gravity. If the sun vanished the earth would fly in a straight line with a velocity equal to its instantaneous velocity at that moment.

          3. Foldi: The thing is spinning at the same rate as the launcher. No that angular momentum won’t just ‘go away’ in an instant with aero forces.

            Physiii: Nice troll. But nobody is actually as stupid as you are pretending to be. Don’t try so hard.

          4. Earth would travel in a straight line if gravity was instantly remove from the solar system. The earth would still spin on it’s axis because of static electric forces (throwing a rock in the air does not make the rock fall apart). Removing electric forces, the rotational momentum would transfer into linear momentum and the earth would fly apart in a torus (donut) like pattern. The thought experiment of instantly removing gravity is a good way to understand conservation of momentum.

          5. HaHa: If it was traveling forward really damn slowly it might have the chance to rotate a few times, as the aerodynamic surfaces are not huge. But with the stupidly high launch speed and so little rotation its not got a chance of tumbling, heck even at very slow speeds its practically impossible to make a dart tumble, and that is a pretty good analogy to the payloads being launched…

          6. Foldi: If you take their numbers (100m diameter 5000m/s speed). It’s released with 16RPS spin (same as the arm it was attached to).
            The forces required to stop that spin in ‘a few times’ would break it. Unless solid metal.

            And that all assumes a 50m long arm spinning in vac at 16 rotations per second.
            Which is nonsense.
            Centripetal acceleration is v^2/r…5000^2/50…5 million m/sec^2…500,000Gs when on the arm. Good luck with that plan. I don’t believe there is a known material that can hold it’s own weight at 50 m radius and 1000 RPM. If it existed, you’d use it to build an orbital tether.

            Let us work out the loads on those center bearings when the arm is unbalanced, for comic relief.

            TLDR; Spinlaunch are pulling numbers from a dark smelly place, but are very bad at math and physics. Likely MBAs.

      2. That bothers me as well. If one grabs a baseball bat and just spins in a circle then when the bat is released the CG will continue in a straight line, but the bat will continue to spin at the same rate around that CG.

        The reason is that just before release the tangential velocity of part of the bat at the smaller radius is less than the tangential velocity of part of the bat at the larger radius. Simply releasing the bat does not cause the slow part to speed up and the fast part to slow down.

        In addition, along the tangent to the motion, at the instant of release one end was heading away from the center of rotation and the other was being turned to the center of rotation, which is what causes it to rotate with the motion of the arm.

        One can picture the latter in this way – if two small items at the nominal ends of the projectile were independently released simultaneously, then they would head in different directions – the average would be the CG of the two items, but the different directions represent the angular momentum.

        The only way to not have angular momentum is for it to have neither a radial dimension or a tangential one – it needs to be a microscopic point.

        1. Notice that it has to travel almost no distance, or time, before its going to be an aerodynamic projectile, its not being spun up near enough to matter in this context – it is effectively zero compared to the magnitude of the intended launch..

        2. I hate to agree with foldi, but, your analogy is flawed.

          >”If one grabs a baseball bat and just spins in a circle then when the bat is released the CG will continue in a straight line, but the bat will continue to spin at the same rate around that CG.”

          You’re describing holding the bat by the handle. The analog to spin launch would be to hold it by the center of mass and pointed tangential to the rotation like a dart. If you were to do this, then the bat would have fairly little tumble.

          A throwing dart is a better analogy, even though they often have fins.

          >”One can picture the latter in this way – if two small items at the nominal ends of the projectile were independently released simultaneously, then they would head in different directions”

          And yes, a very long projectile would have more tumble, but the length of the projectile compared to the the radius of the arm is actually quite small.

          NOTE: I think spin launch is full of BS, and the idea won’t work on earth.

          1. >NOTE: I think spin launch is full of BS, and the idea won’t work on earth.

            Won’t work I can’t agree with as it clearly could be made to work, but won’t be an optimal solution on Earth I think is quite plausible – but being such early days of trying it far to early to really say, actually making the Falcon9 tail landing reusable concept work as well as it does was ‘impossible’ according to most not long ago, as was powered flight once upon a time(etc).

            But purely on paper in an ideal world its a clearly usable system as you can get however much of your launch energy requirements your projectile can survive from the ground, you don’t need to carry it all with you.

          1. Try Mt Chimborazo Equidor as the launch point, just under `21,000 ft on solid ground at the equater about as much earth boost as possible your multi mach spin launcher might just be able to get something up. You would have to size up the device by a factor of 10 allow a large enough payload to be worth it, create a water dump counter weight system for the counterweight offload to smooth out the fling effects on the throwing arm and get some kind of basic ballistic rocket for the forward momentum but it could be done. It comes down the the basic question of with self landing booster already lifting triple this maximum is the juice worth the squeeze?

  2. “Currently, SpinLaunch is running tests on a one-third scale centrifuge that has a diameter of 33 m (108 ft) and forgoes the complex high-speed airlock for a simple sheet of thin material that the test projectile smashes its way through when released”

    The current test system already has the airlock present and in operation: https://mobile.twitter.com/spinlaunch/status/1461534575784443907
    The breakable seal is to allow the airlock to be opened in advance of firing and only rapidly close afterwards. The airlock itself is more to prevent a rapid inrush of air whilst the rotor decelerates gradually (rather than rapidly via air friction and subsequent heating) and has no effect on launch cadence, as each shot requires the rotor to be despun to attach a new payload then spun up again, and you may as well perform the attachment in a shirtsleeve environment rather than under a vacuum.

  3. Not sure you would want to use something like this off a spacestation – its one giant gyroscope as you spin it up, which will effect the whole station, and then at release as well – the space station would have to be rather massive (and stiff) with a rather high launch speed needed for the satellite to make using such a system actually better than the simple spring.

    Off the Moon however seems like a great idea.

    1. Two launchers spinning in opposite directions, one launching a satellite and another launching something of equal mass at the same time, Newton to the rescue again.

      1. That does mean having to loft more mass to the space station in the first place, which is costly – probably at least – I guess waste containers might be usable.

        And its also possible you could use such a thing for dual purpose with clever planning and gain some deliberate course change/boost to reduce the amount of fuel you have to burn.

        But it still seems like way to much of a challenge to use such a launcher on anything much smaller than the Deathstar…

  4. “The primary issue was the inability to develop a rocket engine that could survive the 12,000+ g’s each rocket was subjected to when fired from the cannon.”

    The primary issue the Martlets encountered was casing design, not the rocket motors. Rocket motors that can survive being fired from a cannon are not uncommon: rocket-boosted artillery projectiles and base-bleed projectiles (rocket-booster projectiles with a thrust below drag) are decades old and in active operation.
    One nice advantage of purely mechanical launch over chemical launch is that your projectile does not need to fit into and seal against a barrel in a manner that holds pressure. This relieves you of many design and material constraints. The Spinlaucnh projectile for example can be a perfect Sears–Haack body rather than requiring a boat-tail, driving bands, saboting, can be composed of materials not compatible with chemical propellants (e.g. Carbon Fibre), etc.

  5. Is there really *that* much advantage to throwing stuff into space from ground level versus dropping it from a airplane?

    A little back-of-the-envelope math shows that at 40,000 feet and 500 knots a rocket bolted to an airplane has about as much speed and potential energy as one thrown from the ground at mach 2.3, without the mechanical overhead of having to be built to withstand 10kilo-G’s, the need to withstand the aerodynamic forces a cannonball feels, or the capital costs of building a 100-yard vacuum centrifuge in the middle of nowhere.

    Yes, airplanes cost money, but, they are versatile, and as Virgin and Orbital Sciences have demonstrated, you don’t need anything fancy, you can easily buy an older jet where someone else has taken the depreciation hit. (especially if your parent company is already into aviation and has facilities for servicing large jets)

    Unless you’re real goal is having an excuse to build giant catapults in the desert (which is, admittedly, a very cool hobby) I just don’t see where this pencils out.

    1. How much propellant does a launch vehicle consume to reach 20,000 feet and/or 300 mph?
      Now, have a 747 take your payload that high instead.

      1. Not an exact number, just some rough, back of the envelope math. Actually, now that I look at it again, I may have underestimated.

        A kilo of mass in a cruising airplane at 40,000 feet has about 125KJ of potential energy and about 32KJ of kinetic energy.

        If you threw it up from the ground you’d have to start at about 550m/s (mach 1.6) just to make the height and speed, not counting air resistance.

        Assuming a very well streamlined object of about .2m^2 at 550 m/s that’s a couple of Kn of drag at launch (integrate to zero at 12Km). If the launcher weighs 200K, then each K of mass nets about 60Kj to drag.

        Of course, that means you need more initial speed because you have to have make 157Kj *after* drag loss is accounted for… so. more speed, more drag… not gonna do differential integration over my morning toast…

        so.. guess a number, plug it into the drag equation… close enough… mach 2.3-ish

      2. I meant that you have to invest an amount of energy equivalent to launching at mach 2.3 just to get up to the initial conditions of an aircraft release. Then you have to go from *there* into orbit, so.. lots more, which is why they’re launching at mach 6+

    2. Aircraft launch certainly can make sense, but it wont’ be the right solution for all loads – for one thing the aircraft can only ever be the size and power it is – you won’t build a new one to most efficiently carry x (or be able to at all).

      Where spin launching can much more efficiently launch much smaller than its maximum potential (at least in theory).

      You also have to ask what orbits/flight path your object is supposed to be on – if its a low orbit on a trajectory that is all wrong for the spinlaunch location aircraft is the obvious choice – it can fly to the best launch sites.

        1. Yeah, but you could stick internal bracing in and weld up all the windows or something if it’s for yeeting things above the atmosphere vs being a mach 2 champagne lounge. There weren’t insurmountable problems for remaining in passenger service really with careful maintenance. The biggest incident wasn’t even Concordes fault but some other hunk of junk dropping crap all over the runway.

          1. Concorde catered for the wealthy and businesses. Ticket prices were well out of reach for normal mortals. Operating cost were more than the ticket prices brought in. The only thing that kept Concorde in the air was “prestige”, old empires trying to pretend they still were world class players.

          2. Antti: Once BA and AirFrog stopped trying to be price competitive and went Rolex Concorde was break even.

            It’s not the dumbest ‘I’m so rich’ flex…that would be Chuck’s ‘keeper of the royal toilet seat’.

      1. Why?
        There are much more capable aircraft. Sure they are military, so what?

        Aren’t the surviving concords all in museums anyhow? Maybe you can pick up a really rough concordski.

  6. Regarding the g-force acting upon the payload.
    Wouldn’t it be sufficient to increase the acceleration in steps (adding plateaus) to limit the max g experienced by the payload?
    This should be possible with such a device, unlike when using rockets.

    1. That’s not how centrifugal ‘g’s work.
      It’s not the acceleration of the increase in spin speed. it is the forces you experience simply by spinning at such a rotation rate.

      1. There is the additional disadvantage that the G force in the centrifuge is going to be at a right angle to the main axis of the rocket. Beefing up the rocket structure becomes more complex and heavier than it would be using a linear accelerator.

    2. The problem isn’t the increase in RPM – it’s the spin itself. As long as that thing is spinning at full speed, the object is constantly experiencing maximum acceleration. It’s a giant centrifuge.

      I’m not certain but I think the speed at which the centrifuge spins up should be proportional to jolt, not acceleration.

    3. Thanks for the explanation!
      Physics is definitely not my stronghold, but I’ll try to recall my high-school Physics (or do some research) before I post a naive idea next time ^^

      1. Clearly not ‘physicsman’.

        Gotta question just how much math you got though. Real calc is almost always taught in parallel with physics.

        Did you take business major calcuseless?

  7. >”but that’s a long way from reaching orbit, much less space.”

    Assuming that by “space” it is meant the payload went “above the 100 km Kármán line” the that would be significantly easier than “orbit” and so, their spots should be switched, as the lower bar is mentioned first when saying “much less”.

    I’m surprised that spin launch has gotten as far as they have. But, I’m going to say that this is a fancy/flashy way to get investors dollars. I think their end goal is not space but instead something related to development of high powered centerfuges or hypersonic projectiles.

    The math just doesn’t work in their favor, since altitude matters very little, if it didn’t, all rockets would launch from planes or high altitude balloon. The fact that their rocket will have to be so much stronger means that it will weight enough to not be worth it.

    1. It really doesn’t have to be all that much stronger, if stronger at all – just differently strong – the rocket has to go through max Q, and survive all the atmospheric forces while being a less than optimal shape, must be strong enough around all the staging points, all very specific places for load. The spinlaunch concept means you can be very much more aerodynamic, and much much smaller as you don’t have to carry all the fuel to carry the fuel to carry the…

      The reason all rockets don’t launch from Aircraft is much simpler than you make out – aircraft capable of lifting let alone flying high enough to be worth launching larger payloads/rockets off just don’t exist, and were not very plausible in the 60’s-90’s so didn’t get any development. And a balloon would be such an entanglement risk and have to be stupendously huge to lift the big rockets..

      1. >It really doesn’t have to be all that much stronger, if stronger at all – just differently strong – the rocket has to go through max Q, and survive all the atmospheric forces while being a less than optimal shape, must be strong enough around all the staging points, all very specific places for load.

        According to spin launch, their projectile will be launched at 5,000 mph, which is at least 5 times the speed of a rocket at max q, and the spin launch projectile will be at that speed at ground level, where the atmosphere is 3 times as thick. It may be a gross oversimplification, but it will probably be subjected to 15 times the force a normal rocket has at maxQ.

        Additionally, they have two choices, fire straight up, and bring enough fuel to reach orbit, which will make their rocket weight at minimum 1 ton (thanks “tyranny of the rocket equation”), probably much more since Hydrogen fuel is out of the question. The other option is to fire at an angle, so that the launch velocity helps it reach orbital speed (and needs less fuel), but, that means lots more time at lower altitudes and a lot more drag.

        If you honestly think launching a 1 ton projectile at 5000mph is a good idea, then, good luck.

        1. But it doesn’t have to be stupidly large to carry all the fuel to gain that momentum, thanks to the tyranny of the rocket equation, so doesn’t need to be built nearly as thin in the tanks to avoid too much extra weight to then need even more extra fuel. Doesn’t have the staging separation areas that need to be pretty sturdy.

          Not saying the spin launch vehicle doesn’t need to be strong, but because its so much smaller and can be a better aerodynamic shape for being so, while also not needing all the multistage separation parts, or stiffness across the vast length of the conventional rocket under the launch forces its not unreasonable comparison. Both have to deal with pretty impressive forces, in different ways and with very different limitations in how they can be built…

          In effect any rocket launch with a payload of 1 ton is launching its projectile at 5000mph+ its only how it gets there that is different…

          Not saying I think spinlaunching is the best possible launch method, only that it is valid – to me the best system for launching from Earth is probably very similar lines to SpaceX’s falcon9 – as you can at least in theory with all the red tape involved take one of those and launch land it from almost anywhere on the planet better suited to the desired outcome for the payload, and you don’t need the giant runways a large rocket lifting aircraft would need, just a small launch/landing pad. Spinlaunch you build one at x with y direction and all it can really do is launch stuff on a narrow range of orbits, so the payload would need rather more positional fuel if it wants a different orbit. Which may well be fine for many things, but not as universal.

          1. >”while also not needing all the multistage separation parts”

            You might want to scroll back up to the article and pay special attention to the images, especially the one that shows a cutaway render of rocket.

          2. There is a difference between the concept of spin launching (or any ground based launch system), which is largely what I’m talking about and this one still theoretical implementation…

            Plus one extra stage, that appears to be entirely inside what in most rockets would be considered a payload fairing – so that stage rocket is sort of part of the payload more than the launch vehicle is still far better than the many stages of a large number of other launch vehicles – less stages means less need for tricky to make light AND strong structures and less to go wrong – and there is no denying giving a rocket a vast quantity of its required velocity without needing all the fuel to carry the fuel to carry the mass, or the multiple different rocket motors that will work efficiently at x altitude (etc) makes smaller and less stage launch vehicles possible. If they wanted a single stage they no doubt could do so – though right now the challenge really seems to me to be entirely making a rocket that actually survives the launch, one you iron out those engineering bugs then you can start looking at further refinements…

    1. There was a proposal to build a linear induction motor launcher floated by balloons. In the concept art the launcher rail was in a tube through the middles of a string of large balloons and tethered with some very long cables so it would maintain position. With the top end floating in the upper atmosphere it would provide a high speed jumping off point aimed to the East.

      Unlike building a launcher up the side of a mountain, this wouldn’t rely on suitable mountains being so darn inconveniently located. It could also be lowered to the ground for servicing and have its launch altitude and angle adjusted. Might even be able to aim a bit north and south.

    2. I think a linear accelerator up the side of a carefully chosen mountain (perhaps in Hawaii) might be a reasonable alternative. A long accelerator reduces the required G force in inverse proportion to its length, and a launch at 12,000 feet gets you above 35% of the atmosphere.

      On the other hand, a launcher in Hawaii would probably have environmentalists throwing fits.

      1. “On the other hand, a launcher in Hawaii would probably have environmentalists throwing fits.”

        Just tell them it’s for launching politicians. They’ll be OK with that.

  8. Well this should save NASA some money, get rid of the rockets and just cut a hole in the roof of the centrifuge building! (The astronauts are going to need a pay raise though!)

      1. The Wright Brothers spent relatively little money on their airplane. I see one estimate, cost corrected, to be about $20,000 in 2002 dollars, not including their labor. They did perform several proof of concept tests at very small scales and developed the underlying principles.

        The “crackpots” are those who build large test platforms first – Hiram Maxim built one that had a wing span about the same as the first powered flight distance of the Wright brothers, but since he had not solve any of the control problems he abandoned the effort. Langley failed in a similar way – scaling from a small model without considering the underlying principles.

        The best reason to skip the small stages is so that all problems are big, expensive, and time consuming to address, so that investors cannot see whether reasonable progress is being made. It also justifies the larger number of people. If they had built a 3 meter unit that could reliably hit 5000 feet with a Mach 1 release speed and then a 12 meter one that could release at 10,000G, and so forth, then the problems are much smaller, the spend is much smaller and if they aren’t getting close to either goal at that scale then investors can see that making things larger won’t make the problems easier to solve. But since they went big on this, they can claim the problems might take years to resolve and they all have jobs until then. Same thing applies to DoD acquisitions – go for giant programs that will take a decade or more.

  9. I did a video on SpinLaunch


    The problem with spinlaunch is it doesn’t get you very close to orbit. Based on their patent applications, they only get 2000 meters per second at altitude, which means they need to get 5500 meters per second from their rocket.

    Which is a lot – they need a two-stage rocket to get a mere 200kg into orbit.

    The question is whether customers would be interested in spending the money to harden their payloads to launch on spinlaunch when they could launch their payload on any other launcher without doing that work.

  10. I once did a little back of the envelope calculation for a satellite in LEO. If I remember well it was about 5% potential energy for the 400km, and 95% kinetic energy to swing it around the earth in 90 minutes.

    (We still can’t do it in 80 minutes)

    In the end it means you just can’t gain much by launching a rocket a measly 10km higher from an airplane.

    This also becomes obvious if you compare the size of the fuel tank between that tourism thing that won the Annanasari X prize and barely to managed to hop over 100km high (with no kinetic energy left and immediately falls back) and something that can deliver a payload into LEO and keep it up there.

    It also explains the enormous energy used to further heat up the atmosphere (compared to the size of a small spacecraft, not compared to the atmosphere itself) upon reentry.

    Fun fact:
    If this mudball of ours had about 10% to 20% more gravity in it, we would not have been able to launch any sattellite yet.

    1. I’d very much dispute your ‘fun fact’ of not been able to launch a satellite in those higher gravity conditions yet, if there is sufficient will to make it happen with our current tech level would I suspect even 100% more gravity would still be possible. Its just going to be really really damn expensive.

      1. Interesting thought, but, it really depends, because, having double gravity would imply a thicker atmosphere, or possibly an atmosphere with drastically different composition (would hydrogen and helium escape the atmosphere as well at that gravity?).

        Basically, I think that would be different enough that we laypeople can’t make accurate predictions.

        1. The atmosphere would undoubtably be denser – but that isn’t actually a ‘bad’ thing to making a satellite possible – aerodynamic lift will love it, so the aircraft first stage launch vehicle becomes much easier/more likely.

          I do agree though the myriad of other changes a 2g baseline could create makes its impossible to really know what we could do with our current technologies – at least with out many more defined (or derived) parameters than just double the gravity to start simulations around. But ultimately if you do the Apollo program mentality and throw lots and lots of money and brains at it I have no doubt it could be done, probably even beyond 2g…

      2. Twice the gravity?
        No way!
        Take the Falcon Heavy as an example, apparently a fairly modern rocket:

        Launch weight of: 433+115 = 548 ton.
        Dry weight: 22.2 + 4 + 1.7 27.9 t
        Payload to LEO 68.3 t
        Fuel to other ratio: 1 – (68.3 + 27.9) / 548 = 0.824452 = 82%

        If this mudball has 20% more gravity then you already need 20% more energy (= fuel) to get at the same height at the same speed. However, that is not enough, because you also need more speed (also 20%?) to stay up there. and energy is quadratic with speed.
        So together that is pow( 1.2, 3) = 1.73 the amount of fuel.

        And unless you can find a fueling station halfway you have to start with an extra:
        0.73 * 451.8 = 329.814 ton of fuel.
        So if you replace all the payload with fuel you still need an extra:
        329.8 – 68.3 = 261.5 ton of fuel just to get an empty rocket up there.

        If you wish, you can also add to that that it was an enormously expensive task in the late ’60-ies, and with just this 20% extra gravity it would have skyrocketed the costs yet again, and the space race quite likely would not have started in the first place.

        Atmosphere is not very important, It’s just a thin layer that only creates a little bit of extra drag when you’re still going slow.

        A real rocket scientist (or Kerbal) would probably calculate with the specific impulse of the fuel, but what really kills it is the cubic equation of the combination of more downward pull and needing more speed.

        1. But you wouldn’t with current tech in 2G actually launch from the ground in the same way as the Falcon 9 does, most likely anyway. As the denser atmosphere makes aerodynamic lifting so much easier, so you could launch something possibly even larger than the falcon9 from a very high altitude, off an aircraft practical enough size – and when you look at how frankly janky and beyond the comfortable the Apollo program was there is no reason to believe the same couldn’t be done if there is the will to do so.

          I do agree though in the 60’s the space race would most likely not have started in this scenario, it might be technically possible to stack enough rocket booster with 60’s tech to get a tiny cubesat to orbit, but cost to reward is so poor – though jet engines would likely get much much more development effort… So things like the U2 and SR-71 would likely remain the primary military expenditure/research point.

          But talking about todays tech at 2g and with so many years extra tech on the 60’s baseline to line getting to space I really don’t see it as a big deal now, even with 2G to be in space somewhat – but that doesn’t mean ISS, voyager probes big heavy rovers to Mars, just getting some stuff to orbit, the weather/spy satellite and satellite TV type stuff. The how its done absolutely would be different, but the possibility to do it definitely exists.

          I’d think in a 2g world by the late 80’s early 90’s (assuming the cold war or something similar to keep military development and such expenditure at a high priority) the first spy and communication satellites would be launched, small little things almost certainly launched from something SR-71 or X-15 like aircraft that has already got them up to very high velocity and altitude so the rocket needs not be huge to bump them up the rest of the way.

          1. Even now we need 3 stages to get up there. 20% extra gravity would double the amount of fuel needed. 2g would need 8x more fuel, and you’ve shown nothing except some vague “absolutely possibility” to counteract that.

            Also, why do you assume the atmosphere would have to be denser? On a planet with 2g you could as well assume ground level pressure is the same, but with a thinner layer. But it does not matter much. I was quite surprised that we could build something that can fly on Mars, and a factor 2 denser (towards the other side) matters very little. Aeroplanes can’t even fly fast at low altitude because there is too much air resistance. But it all does not matter, because most of the energy you need is in kinetic energy to get up to speed. So what would really help is a planet with shorter days.

            Speed is relative, SR71 / X15 is not even near orbital velocity or height.

            But you may keep on assuming.
            Ignorance is bliss.

          2. Who cares about flying fast at low altitude – that has no bearing on getting to space, as space ain’t low altitude… And we use multiple stages not entirely because we need to, its all engineering choices – do you carry a less efficient at high altitude rocket higher into the flight to avoid a stage or put a stage in so you can have a better rocket at this stage of the flight? Is it worth shedding the mass/drag or improving the COM/COP caused by this much empty fuel tank at this stage vs the complexity and weight of a stage separation?

            We do need further details to narrow it down and actually do any realist simulation, why is it a 2g world? Heavier core? Larger planet? etc. But its a fair assumption to say denser atmosphere, which means if we just transplant one of our current tech aircraft to that world it should be able to fly much higher, or carry much more weight, and design an aircraft for that denser atmosphere you can pick the balance of lifting a heavy rocket high and fastish vs aircraft size vs smaller rocket launched from even higher and faster.

            Never said Sr71 or X15 are near orbital velocity they are just examples of aircraft that can fly in the thinner higher air than most and have reasonably high speed, if you assume launching off an SR71 type aircraft on Earth you already have cleared the vast bulk of the atmosphere – the bit the rockets really hate with all that drag, so suddenly you don’t need nearly as much fuel in your rocket to overcome that, and you already have more useful momentum at rocket ignition than the ground launch rocket will get its payload to for a very long period and vast quantity of fuel into its flight (and depending on just how many stages you throw in you are still going to be hauling lots of the dry mass of the fuel tanks for much of the lower altitude flight, which high altitude launches also largely negate as you are only flying through thin and then null atmosphere so can have a more ideal rocket for the job the whole time AND already have a good velocity in a very low drag environment).

            Also who cares if it needed 50x the fuel, as long as you are still able to actually get net lift (as in it doesn’t have to be heavier than its thrust output) you can just stack a honking great rocket if that is what you wish to do, and with the benefits of getting satellites into space the only way it wouldn’t happen is if the world is so blissfully peaceful and content, with nice weather at all times, and no need to communicate a long way over the horizon that nobody wants to put up the expenditure…

            I AM NOT SAYING space would be populated exactly like it is today, BUT that there is no way with our current tech to say we wouldn’t have stuff in space despite a higher G – its just too damn useful to have it
            – Want to keep an eye on x regime cold war mentality style – then the satellite is way better than relying on an aircraft – much much harder to catch/shoot down, sees a much wider swath, its always up there sweeping away for no ongoing costs, no maintenance of the airframe, paying the pilot, ongoing fuel costs etc, launch a few and you can have eyes on more of their antics far more often than you could if you put half a nation into the seats of spyplanes…
            – Want to communicate with your warship/aircraft/Odd Japanese motorcycle parts supplier vastly over the horizion?
            Or have decent weather forecasting – the list of things its nearly impossible to do without orbital hardware is very long, and the benefits are huge – so the cost to make it happen isn’t a problem. By that sort of argument Apollo wouldn’t have happened yet – its of no real practical use and stupidly stupidly expensive, and right on the ragged edge of what was possible then, and still not simple now…

  11. nobody will read this cuz long thread… but what would be the major reasons for not using a long track with a gentle curve at the end? if ya put it in a tube or roller coaster style track, i would think you could get some pretty decent altitude for smaller payloads and reset for launch faster and could choose from a plethora of propulsion options. how much less force would it take to get some speed before turning vertical? could even start the payload on top of a hill to get that first bit of free momentum. i dunno, im not mathematically inclined enough to figure out the cost benefit structure. otherwise im sure someone woulda tried it already.
    just saying, rather than 1 massive rocket for cubesats, use less cubesats per payload and find a much cheaper way to get the first bit of height for cheap without a highly complex blender flinging space junk.

      1. Indeed, a long track is long, so will probably cost more than most launch systems just for the land area it covers, even more so if you want to put it in a tube with no air in to really be able to get it going really fast (which you probably want to do as much to keep wildlife and debris out as well – can you imagine a FOD at 1000MPH+). And probably will get more complaints from the neighbors as an eyesore…

        The big advantage it seems to me of a long track concept is you can launch a much wider size range of rockets off it – if its got beefy enough drive system to take the higher spike draw it won’t even be launching them slower, just using more energy.

        But the spin launch has the advantage of being reasonably compact and self contained, almost certainly cheaper to build, likely cheaper to run.

        And in both cases the G force and aerodynamic forces are going to be similarly rather high I expect – the spinlauch should have more effective G from the rotation, but ultimately you can only make a track so long so the acceleration G forces on a track launch will still have to be rather significant for it to make any sense.

        There are a variety of smaller launch systems targeting ‘cubesat’ type payloads, but its usually looking cheaper to hitch a few cubesats into a launch on a larger rocket that has spare capacity than fly a dedicated smaller mission.

  12. I wouldnt think it would be a good idea to mount this on anything in orbit. Newtons 3rd law and all that, you’d have a hard time balancing out spin that would otherwise cause the object (space station) in orbit from spinning in the opposite direction. Even perfectly balanced spinning a large enough mass at that speed, miniscule differences in balance would cause chaos. As it stand the springs on the ISS have a force that pushes it slightly in the opposite direction (even considering the cube sats mass vs. the ISS).

  13. Rocketry engineering seems well used to using hydrogen as a propellant. Why not use it in a balloon too?
    Lift the whole rocket up to ~30,000 feet or whatever, then light it up, leaving the balloon behind.

        1. Up isn’t the problem.

          The problem is “going sideways real fast.”

          As XKCD says, getting to space is relatively easy. It’s staying there that’s hard:


          Using a balloon gets you up, but it doesn’t get you fast.

          The balloon will save a little on the fuel because you don’t have to punch the ship through the dense lower atmosphere.

          You still have to use the rocket engine to get the rest of the way up and to get up to speed.

          The balloon lift is complicated and doesn’t save enough fuel to make it work handling the complexity.

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