Eh?

A centrifuge large enough to contain a football field will whip a rocket around in circles for roughly an hour, its speed steadily ramping up to more than 5,000 mph. The vehicle and its payload—up to 200 pounds’ worth of satellite—will experience forces that, at their peak, will be ten thousand times stronger than gravity.

Err, no, don’t think so. The reason it’ll take an hour is because no one wants to subject anything to 10,000 G, right?

66 thoughts on “Eh?”

  1. There is a minor question – if the counterbalance is spinning at the same speed as the rocket [or it is N times the weight at 1/N times the speed] and it is let go at the same time going vertically down when the rocket is going vertically up, will it cause a minor earthquake?

  2. The maths seems right, they do mean 10,000G – note it is a very large and very fast centrifuge. The economics less, they say they will be able to launch 200lb to orbit for $500k, so the ‘lots of small satellites business’, sounds good until you realise SpaceX is launching 60x500lb StarLink satellites at the moment for $57m, so can probably do 120x200lb for $57m, or $475kper satellite.

  3. Er, yes.

    If you put something in a centrifuge and spin it up then it’s subject to centrifugal force. That’s what centrifuges are usually for.

    And the article specifically talks about how the payload will be subject to these forces –

    “Over the next few years, the team ran hundreds of high-speed tests. Most of them were to study and improve the system, but some were to mollify skeptical investors and potential customers who didn’t believe a payload could withstand the extreme forces. The team sent solar cells, radio systems, telescope lenses, batteries, GPS modules, and control computers whirling at high speeds; they all survived with little to no damage. In one test, Yaney attached an iPhone to the tether and spun it up until it experienced forces 10,000 times stronger than gravity. Afterward, he used the phone to FaceTime a colleague. Each test was a step, however small, toward space.”

  4. Yes, 10,000 times the force of gravity is correct – they”re talking about the centripetal force (v^2/r) of something going that fast around a circle, not the Euler force that would accelerate it to a linear 5,000mph.

  5. An object being spun in a centrifuge is necessarily undergoing acceleration, measured – if you like – as a multiple of g.

    It matters not whether it took an hour or an aeon to reach its steady rotational speed.

    Your guide is (ω^2)r. This is schoolboy stuff.

  6. So… They’re going to accelerate the launch vehicle to 5,000mph in a vacuum, OK so far…

    Then, at the right moment, some form of portal/door has to open quickly enough to allow the projectile through, then shut again before the inrush of air destroys the vacuum and (probably) ignites the kevlar boom from sheer friction… Then… The projectile hits a wall of air at 5Kmph, I can’t even begin to calculate the “megatonnage” of the sonic boom or the heating that the projectile will encounter, let alone the g-force of the deceleration caused by aerodynamic drag…

    Just getting a, say, 10-foot-wide airtight door to open and close in a couple of microseconds is going to be some feat of engineering.

    Sounds damned exciting, almost Elon Musk-like in it’s “off-the-wall-ness”.

    I will await further news with considerable interest!

  7. The pic shows a linear bit tangential to the cylinder, so there is probably an air lock, but synchronising the doors at 5k mph will still be interesting.

  8. There is a minor question – if the counterbalance is spinning at the same speed as the rocket [or it is N times the weight at 1/N times the speed] and it is let go at the same time going vertically down when the rocket is going vertically up, will it cause a minor earthquake?

    They’ll put a cushion under it

    Then, at the right moment, some form of portal/door has to open quickly enough to allow the projectile through, then shut again before the inrush of air destroys the vacuum and (probably) ignites the kevlar boom from sheer friction… Then… The projectile hits a wall of air at 5Kmph, I can’t even begin to calculate the “megatonnage” of the sonic boom or the heating that the projectile will encounter, let alone the g-force of the deceleration caused by aerodynamic drag…

    Build it on the Moon! Problem solved.

  9. I’m not a physicist, but ISTM that the object being fired won’t stand being 10,000 its own weight without breaking or malfunctioning somehow…

  10. bloke in Germany in New Jersey

    For the counterweight, I guess the calculation is that wrecking one centrifuge per launch may still be cheaper than current ways of doing it. And if the centrifuge is sufficiently in the middle of nowhere, there will be nothing else of value in its path to wreck.

  11. The plastic tip on rifle bullets at 2k mph begin melting in less than a hundred yards from the muzzle.

    o Load crushed from lateral acceleration during rotation;
    o Load crushed from longitudinal deceleration at launch;
    o Load burned up from air friction (note same effect as re-entry, only at launch)
    o Launch system destroyed at every launch;
    o Horrendous noise problem (at launch and flight);
    o Trajectory control when outside air explodes in at launch;
    o Solves no problem.

    Other than that, good idea.

    There were Cold War rumors that the Soviets had a rail based launcher. Initial acceleration powered independently from the launch vehicle. The rail car would get the rocket going fast, then go up a ramp to orient the rocket skywards. A good idea. In theory. The rocket having to lift its full launch weight is inefficient. Think Saturn 5.

  12. The 10,000 G is the ‘centrifugal’* force of going round in a circle, as others have said. It is steady state, once the rotation is constant. Sounds interesting as a test facility.
    It takes hours to get up to speed ‘cos whirling that mass around that fast will take a lot of energy, and a very big motor.

    But I don’t understand the ‘launch’ aspect, quite apart from the door mechanics.
    To get into orbit, you do NOT go up. You go sideways, very fast. The only point of any vertical ascent (as per Cape Canaveral etc) is to get out of the soup of an atmosphere. You flip over as soon as you can. Going up is a detour, and wastes energy if orbit is the aim. On the moon, you could launch using a linear motor on the surface, no up at all.
    So if this thing fires upwards, what the point? You go up, out of the atmosphere, then fall back down again. If you want orbit, you need to go sideways, and that is far far far harder than the going up part. Everything you fire up is a rocket, not much smaller than you’d need to use conventionally.
    If you fire this thing sideways, direct to orbit, you will get a great meteor shower, but nothing will survive to orbit.
    (although see Cody’s Lab and the Atomic Manhole Cover)
    Up: To get to space – Karman limit, 100km = mgh = 1 million joules/kg.
    Sideways: To get low orbital velocity, of 8km/sec = 0.5mv*v = 32 million joules/kg.
    So the going up bit is 3% of total on an exponentially difficult task.

    But it will be immense fun to watch this thing fired. Is Jeremy Clarkson or Dick Strawbridge involved?

    * yes, it’s ‘centripetal’ to pedants :), but everyone understands the term.

  13. To quote from the article “the rocket only has to fire for a minute”.
    Have you watched a SpaceX launch video…..not much longer.
    And a conventional rocket doesnt need a fuel tank that can take 10,000G (sideways!!!!) nor an ablative heatshield to survive the ascent.
    It stinks. Cannot Recommend A Purchase.

  14. …and yet, and yet.

    The US military is said to have launched things up fast enough that they’d orbit if they’d been pointed in the right direction and had a bit of adjustment capability – gun-launched stuff. Verne lives! There’s that Manhole…

    There’s even a Wikipedia page on space guns…

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

    And the launch problem is a bit worse – you gotta open two trapdoors – one for the missile and one for the counterweight.

    I think the best perspective on this effort is “brilliant eccentricity” rather than “idiots; it canna work”

  15. Good point, TtC. 199 pounds of the 200 pound payload would have to be structural to withstand the g forces.

  16. BiT:
    “Up” only works if its faster than escape velocity (25,000 MPH or 7mile/sec roughly).
    That’s 5 times what they are shooting for. And the sonic boom will be impressive.
    The speed they claim to need (5000 MPH) is just enough to reach 200km height, with no air resistance. In reality, almost all that kinetic energy will explosively convert to overpressure in the first 1000 metres.
    It’s bound to annoy the neighbours in the next continent.
    But even without that drag, the launch is converted to the necessary height only, you need another 17000 MPH to stay in orbit.

    Our teams had only 2 days in the Scrapheap to construct….

  17. One more thing Jackie!
    10,000 G sideways. Assume diameter of fuel tank =1meter and fuel density roughly 1 like water.
    Then hydraulic pressure on lowerpart (outside of centrifuge) will be same as depth of 10km = 1000 atmospheres of pressure higher than the side of the tank nearer the axis!
    That’s some tank. And when you release and stop circling, the pressure is equalised, that’s some hydraulic shock wave! Oh, this is gonna be fun to watch.

  18. Tim the Coder – in fairness, the diagram in the article shows a launch angle of 30° (maybe 35°?), not vertical. None-the-less, synchronizing the airlock opening, the structural loads on the rocket, and the sonic boom all look to be insoluble.

  19. ““Up” only works if its faster than escape velocity (25,000 MPH or 7mile/sec roughly).”

    Uhhh . . . no. That is for orbital velocity. Theoretically, you could go vertical at 1 mph and eventually escape.

  20. Since you’ve fisked it thoroughly on physics grounds, I wonder at the finances. Are we looking at a lot of investors losing their shirts while the promoters live high on the hog for a while. One for the SEC?

  21. C4 News in full on Funeral mode – dark backgrounds, sombre reporting

    No, not a Royal has died; Brexit we leave ‘Europe’ in 4 hours

    They’re contemptible barstewart cnuts

  22. Fuck me! I already lighted the fucking Sabbath candles and here I am! Listening to fucking Elton John. Probably got my bloody dairy and meat utensils all mixed up – too drunk, can’t tell.

  23. ROFL

    Yaney had the ideas and Hampton the construction skills, but they still needed some aerospace engineers.

    college students had gathered to test their rockets. The duo was hoping to recruit a few of them.

    Yaney “Wanna work for my firm, good pay and fun?”

    Any student would grab the money and not say “You’re bonkers”

    Former employee also cited the inexperience of some of the leaders. “The foresight to predict many of the issues that are going to happen was definitely lacking,”

  24. @john77

    once a rocket is spinning at launch speeds, an exit port in the centrifuge will open for a fraction of a second, sending the rocket shooting out. According to patents filed by the company, a counterbalance spinning opposite the rocket gets released at the same time, preventing the tether from becoming unbalanced and vibrating into oblivion

    @Tim Worstall January 31, 2020 at 1:10 pm

    Not quite what I mean. 10,000 G is the acceleration, not the speed.

    Once spinning at max speed it will hit 10,000G and remain 10,000G until speed reduced

    Wired writer description is correct in para beginning “When I visited this past fall, SpinLaunch…”

    @BiG

    Self-destruct not their model:

    “Yaney predicts the mass accelerator will be able to do five launches a day”

    Seems Yaney thinks “Back to the Future” is a docu-drama

  25. 200lb X 10,000g = 2,000,000 pounds.

    This is going to be one huge structure!

    KE = 1/2 mv^2

    200 pounds at 5000 mph equal 167,000,000 pound feet.

    [What is that in Hiroshima Bombs?]

    As a safety precaution, no one will be allowed with 20 miles at launch time.

    Using – miss using? – an online calculator, using an arm length of 10m, to revolve to produce 10,000g, would have to do 946 rpm. 15.7 per second. OMFG !!!

    A blur.

    “Release the counterweight!”

    How many stories down will that penetrate?

    5 launches a day? It’ll take ’em a week to dig up the counter weight.

  26. 5000mph, seems reasonable, prima facie, for a straight up shot to escape the well.
    Good idea, all in all.
    Ah in a vacuum. Ok, so lets look at air resistance force, which it will have to go through to reach space…

    F(air) = 0.5 * density * drag coefficient *cross section Area * v^2

    Air Density at sea level = 1.2 approx
    Lets be generous for drag coefficient and say 0.01 ( a quarter of that for a streamlined body)
    Lets figure out per cross sectional area, so 1m^2
    V = 5000mph = 2235m/s…

    So per m^2 area, equates to approx 30kN resistance. Or 3 metric tonnes.
    Hitting all at once on transition to atmo.

    A quick duckduck turns up an average satellite size of 4.6m diameter of a cylinder when packed. Lets be generous and say 4m.
    So area of approx 6.25m^2
    A force of nearly 19tonnes.

    Yeah, good luck with that.
    Unless they’re planning on building a vac tube up to space… In which case, why bother with the centrifuge? Just build a bloody elevator.

  27. …TimTheCoder

    Yes, yes, yes. Indeed. Issues.Real ones. Hard problem. But massive eccentricity (no the centrifuge, hopefully – the people) rather than there’s no way this can work. It probably won’t work as intended, but…

    But I’d use a solid propellant. Multiple chunks. Fire ’em off in a pattern to get the directionals. Not as elegant as classic liquid, but much happier to be 10KG’d.

  28. Gamecock

    No need to dig up the counterweight. It won’t have fallen down into a hole – it’ll have exited the centrifuge. Being much more massive and much closer to the axis than the payload, it won’t leave at 5000 mph, but I wouldn’t want the job of standing outside and catching it, either.

  29. ‘Being much more massive and much closer to the axis than the payload, it won’t leave at 5000 mph, but I wouldn’t want the job of standing outside and catching it, either.’

    Ever how they arrange it, it must counter balance 2,000,000 pounds. At full tilt. When the machine is at rest, it must support the counter balance’s weight. It must also support it during deceleration, without the payload mass to counter balance it! Almost a thousand RPM with nothing on the other end.

  30. “Ever how they arrange it, it must counter balance 2,000,000 pounds. At full tilt. When the machine is at rest, it must support the counter balance’s weight. It must also support it during deceleration, without the payload mass to counter balance it! Almost a thousand RPM with nothing on the other end.”

    why not put a payload on either end and fire two satellites at a time?

  31. ”There were Cold War rumors that the Soviets had a rail based launcher. Initial acceleration powered independently from the launch vehicle. The rail car would get the rocket going fast, then go up a ramp to orient the rocket skywards.”

    They must have been fans of Fireball XL5.

  32. Mr Womby – the ramp could be very low ramp – maybe 30 feet in one mile rise in height.
    What they need to do is aim for empty sky. Could do multiple launches a minute with decent equipment – just needs sufficient speed to leave the planet. Trajectory can be calculated.
    Ideally have the end of the launcher as high as possible – top of a mountain or very near its crest – to reduce air pressure.
    But with sufficient speed and shielding even that can be bypassed as a problem.

  33. Martin, Mr Wormby,
    I also found myself remembering Fireball XL5! Commander Troy Tempest wasn’t it? Ah!!
    But you certainly don’t want a bend in the launcher, not at hypersonic speed.Must be dead straight, although can have gentle slope.

    Size of a mass driver is surprisingly short, especially if not launching fragile people (or if you do, put them in a tank of water):
    v*v = 2as, and for orbital speed, v*v = 64million.
    So 32 km of track at 100G, or 64 km at 50G. 128km at 25G where immersed people are feasible. Maglev trains territory.

    Major problems are doing it high enough to get above the air: Heinlein proposed Tibet, in “The Moon is a Harsh Mistress”, and the need for some ablative heat sheilding for the first incandescent (and a little draggy) bit. Ouch.
    Secondary problem is the titanic sonic boom (as per the spincon described above), but Tibet solve that too, on the grounds its mostly empty, and the current landlord doesn’t care anyway. Humph.
    Moon and Mars maybe, for Earth, I think its rockets or elevators.

  34. Don’t understand why they needed to set up a company to build anything.
    Just ply the local physics department with enough coffee and get them to run some gedankenexperiments and simulations.
    If you want to get something into orbit relatively inexpensively (in terms of cost & energy) then I think a space elevator would be a more likely route.
    But yes, I can see how it might be entertaining for a young experimenter to be involved in such a thing. Just wouldn’t like to be one of the neighbours!

  35. ‘why not put a payload on either end and fire two satellites at a time’

    Excellent idea!

    I was thinking about timing. If my above calculation is reasonably close, this thing is spinning at 15 revs per second. Timing the release is going to be very difficult; even a slight error could be catastrophic.

    TWO payloads may be the perfect solution. Timing may be impossible, but if they can perfect the timing for one . . . .

    At 15 revs, it will take 1/30 of a second for the other load to get around to launch position. In normal physics, that seems short enough to avoid problems. But I should think that at 10,000g, a lot can happen in a 30th of a second.

  36. why not put a payload on either end and fire two satellites at a time

    Doesn’t it have to be angled slightly to fire the payload towards the sky – at least higher than the horizon (unless you have a totally flat plane horizon to horizon to launch from)? But then at the same instant the other end would be travelling towards the ground.

  37. “at least higher than the horizon (unless you have a totally flat plane horizon to horizon to launch from)? But then at the same instant the other end would be travelling towards the ground”

    That’s easy – just put it on top of Mount Everest.

  38. There were Cold War rumors that the Soviets had a rail based launcher. Initial acceleration powered independently from the launch vehicle. The rail car would get the rocket going fast, then go up a ramp to orient the rocket skywards. A good idea. In theory. The rocket having to lift its full launch weight is inefficient. Think Saturn 5.

    There was a documentary series about it:
    https://www.imdb.com/title/tt0055673/
    🙂

  39. I was thinking about timing. If my above calculation is reasonably close, this thing is spinning at 15 revs per second. Timing the release is going to be very difficult; even a slight error could be catastrophic

    If that 15rpm is right, that’s actually quite trivial for modern systems.
    Think of a car engine, they rev up to around 7000rpm in a fairly standard family petrol. Sports bikes will rev to 13,000rpm.

    The difficulty would be in getting the door to open and close quickly. I would imagine you’d have to have a large gap in a sheet of metal that passes through the tube. Alternatively you could not bother closing it again after. Would make life easier – just mount the door on rails with explosive to move it quickly.
    Still have the problem of a massive air impact though…

  40. PF, good idea about installing it at a higher elevation (though not necessarily Mt. E).

    Makes me wonder why current rocket launching isn’t done at higher places.

    U.S. uses Cape Canaveral (sea level) because of distance from equator. The closer the better for equatorial flight. But other launch site is Vandenburg AFB, about only 400 ft elevation. Going higher to launch seems to be a no brainer.

    But I’m not a rocket scientist.

  41. “Makes me wonder why current rocket launching isn’t done at higher places.”

    Because there’s no point. Rockets don’t go fast when they launch, so air pressure isn’t really an issue. You need to go up to 100,000 feet or so anyway, before you can start going really fast, so even starting on Everest is only a small benefit.
    Most rockets have to throttle down till they get there. Max Q and all that.
    As I mentioned before, the energy requirement for gaining height to space is only 3% of that necessary for gaining orbital velocity sideways, so a tiny increase in launch height isn’t worth the shipping difficulty (& downrange risk).
    Very different if launching ballistically of course, then mountain tops are beneficial.

    For rockets, you need somewhere with lots of empty space (ocean) downrange, and with good canal connections to bring in large items: boosters etc. For equatorial orbits, on the East coast, near the Equator (1000 mph benefit). For polar orbits, no equatorial gain,so harder to acheive.

    I still think the Giant Spin Drier is a scam. And is it made by Hotpoint?

  42. Thanks, TtC. Good info.

    Yes, launches from Cape Canaveral are always aimed out to sea for safety.

    Vandenburg is also coastal.

  43. “air pressure isn’t really an issue.”
    Air pressure is very much am issue. The optimum shape for a rocket nozzle optimised for exhausting into sea level air pressure is a very different shape from one optimised for exhausting into low pressure or vacuum.
    And, of course they’re launching rockets from high altitudes now. From a carrier aircraft.

  44. BiS;
    You are right, I was thinking of the front end & drag. At the back end, there is indeed a big influence of outside air pressure in the nozzle expansion ratio: one advantage of staging is that each stage can suit this, whereas SSO cannot.

    Airlaunch is partly to provide some of the first stage lift out of the troposphere by wings, the effect is best for joy rides to the Karman limit and less relevant to orbital launches. Pegasus is an airlaunch to orbit, but very small. And yes, that’d be enough to get the expansion ration common.

    An airlaunch carrier for a serious booster (Falcon 9, never mind Falcon 9 Heavy class) would be humungeous. Love to see it! Paul Allen was building such a thing, but I think it died with him.

    The major benefit of airlaunch is the mobility of the launch point: can get nearer the Equator, and well away from populated areas. Though you still have to take off from somewhere carrying what is effectively a massive munition: problems of its own.

    What a topic this spin drier is turning out to be 🙂

  45. Yes, launches from Cape Canaveral are always aimed out to sea for safety.
    Vandenburg is also coastal.

    Launches intended for equatorial orbit always head east – nobody AFAIK has put a satellite into a retrograde orbit. So Vandenburg is on the ‘wrong’ coast, but debris from a failure probably comes down in AZ where it’s unlikely to hit anyone/thing :).

  46. “Makes me wonder why current rocket launching isn’t done at higher places.”

    The rotation speed of the earth is greater at the equator. That’s speed you don’t have to fuel for so I’d assume that, combined with it being a good idea to launch over the sea which is at sea level.

  47. Vandenburg is good for polar orbits,usually launched just west of north to get solar synchronous orbit.
    I read somewhere that SpaceX are getting permission to launch into polar orbits from Canaveral: they have so much spare oomph available they can dog-leg the trajectory so that bits don’t fall on anyone’s head (if the launch or booster recovery fails) and the middle bit can still be sea-landed. They then turn left a bit and angle up over empty bits of Canada.
    It’s a bit like Sagan’s comment on putting Bach on Voyager (or was it Pioneer?): “Now that’s just showing off.”

    I’m no fan of Musk, but SpaceX is quite something. Was it only a few years ago, recovering a booster and reusing it was considered a joke?
    One for the business textbooks: is this progress achieved because Musk is so busy with Tesla?

  48. @Chernyy_Drakon

    “Sports bikes will rev to 13,000rpm”

    16,000rpm and F1 > 20,000rpm

    @BlokeInBrum

    “I can see how it might be entertaining for a young experimenter to be involved in such a thing”

    #metoo, high pay, cutting edge on CV, build and test any crazy thing you want – a dream job

    @Tim the Coder

    Hotpoint? No Whirlpool : )

  49. It feels as though this would be far more useful as an ICBM launcher than a satellite launcher. A centrifugal force of 10,000G is absolutely correct – ideally, you’d build an underground tunnel with a 500-mile radius and take that force down to ~15.5G for a 100kg payload travelling at 25,000mph – but if all you’re doing is throwing a heavily protected multiple-warhead nuclear cluster bomb at a distant target without requiring a load of solid fuel and navigational electronics, this will probably work, as long as you can find something that can withstand turning the air to plasma on initial release.

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