
SpinLaunch raises $40M to build a machine to catapult objects into space - mpweiher
https://www.bloomberg.com/news/articles/2018-06-14/this-startup-got-40-million-to-build-a-space-catapult
======
nickparker
So, I worked at Hyperloop One for a time, and that experience made me
skeptical of the type of complaint I see in this thread.

Yes, a high school physics student can tell you the accelerations will be huge
unless the loop is too, and a smart one can explain you need a circularizing
burn.

But, contrary to popular belief investors aren’t total idiots who neglect
basic questions. Hard tech companies do face major challenges of course, but
they aren’t the ones armchair engineers on HN can point out with 5 minutes
thought.

So instead of indulging in the “hurrr it’ll never work” superiority stimulus,
I’d Like to point out some rays of hope:

I don’t think “catapult” means “solid arm on an axle spinning at high speed.”
I’m guessing it actually means a large-ish diameter magnetically levitated and
accelerated loop. That makes much larger radii possible: at 1 mile you’re
looking at ~300g acceleration, 150g at 2 mile. We have loops much bigger than
this with much more complex magnetics and vacuum components in our particle
accelerators, so this wouldn’t be terrifyingly novel tech.

Those accelerations are big but not horribly painful to make a smallsat stand
up to. We have guided artillery shells that bear 15,000g launches.

I think it’s somewhat feasible. I also think big fully reusable chemical
rockets will beat this thing on cost and ease of use, but i don’t think it’ll
fail because of armchair physics.

~~~
JumpCrisscross
> _We have loops much bigger than this with much more complex magnetics and
> vacuum components in our particle accelerators, so this wouldn’t be
> terrifyingly novel tech_

Last cost estimate I saw for a reasonably-sized slingshot was $10 billion,
which is in the neighbourhood of the LHC's €7.5 billion accelerator +
accoutrements cost [1].

Some of the skepticism in this thread, particularly regarding the technology's
core viability, is premature. But economic scepticism is warranted. I would be
skeptical of a space elevator project without mass-manufactured carbon fibre;
I am skeptical of a slingshot proposal without cheap superconductors.

[1]
[https://en.wikipedia.org/wiki/Large_Hadron_Collider#Cost](https://en.wikipedia.org/wiki/Large_Hadron_Collider#Cost)

~~~
black6
Keith Lofstrom wrote about the electronics costs associated with a mass driver
back in the '90s [1]. It's dated so some of the base costs have gone down, but
it's still a good primer.

[1]
[https://settlement.arc.nasa.gov/Nowicki/SPBI1SI.HTM](https://settlement.arc.nasa.gov/Nowicki/SPBI1SI.HTM)

------
JumpCrisscross
The tyranny of Tsiolkovsky's rocket equation [1] results from the need to burn
fuel now to accelerate fuel for later. "Catapulting" sidesteps this issue by
energizing on the ground.

In selling away the rocket equation you buy yourself drag. Lots of energy up
front means lots of drag. Overcoming that drag means more energy and, hence,
more drag. The middle child of this solution is tremendous G force.

You can't slingshot complex things into space. Pretty much just fuel and raw
materials. That means you need in-space (a) refueling and (b) additive
manufacturing capabilities. There are teams working on both problems, though
they are presently in the domain of science versus engineering. Perhaps that
will now be incentivized to change.

[1]
[https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation](https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation)

~~~
arkh
> In selling away the rocket equation you buy yourself drag. Lots of energy up
> front means lots of drag. Overcoming that drag means more energy and, hence,
> more drag. The middle child of this solution is tremendous G force.

Would it be possible and useful to do it with a 2 payloads system: one dumb
piece of material first which can take lot of G followed closely by your
"fragile" payload using its draft?

~~~
JumpCrisscross
> _followed closely by your "fragile" payload using its draft?_

G-forces [1] are a consequence of acceleration. An accelerating object will
experience g-forces in an atmosphere or in a vacuum. ("Drafting" [2] is an
aerodynamic process by which a following object exploits a leading object's
slipstream to reduce the former's drag.)

With a slingshot, the destructive force is the g-force inflicted by the
acceleration. (With a rocket, the destructive forces are mostly vibrations and
aerodynamic stress.)

Note that a slingshot doesn't require lots of Gs. One could use a super-long
slingshot to achieve the necessary velocity. But super long is super
expensive, so high Gs it is.

[1]
[https://en.wikipedia.org/wiki/G-force](https://en.wikipedia.org/wiki/G-force)

[2]
[https://en.wikipedia.org/wiki/Drafting_(aerodynamics)](https://en.wikipedia.org/wiki/Drafting_\(aerodynamics\))

~~~
JoeAltmaier
I can imagine a heavy dead weight accelerated in the slingshot. Once released,
it drags a cable, carefully laid out at an angle, with the payload attached.
That payload would be accelerated into line behind the weight over a brief
period. Taking fewer Gs and only once.

Very long cables are a lot cheaper than very large slingshots?

Anyway just thinking out loud.

~~~
JumpCrisscross
> _Once released, it drags a cable, carefully laid out at an angle, with the
> payload attached_

Unless your cable were elastic, this would not materially change the payload's
acceleration. That said, you might find skyhooks [1][2] interesting.

[1]
[https://en.wikipedia.org/wiki/Skyhook_%28structure%29](https://en.wikipedia.org/wiki/Skyhook_%28structure%29)

[2]
[http://adventuretime.wikia.com/wiki/Skyhooks](http://adventuretime.wikia.com/wiki/Skyhooks)

~~~
JoeAltmaier
Of course it would. Like a lever has different forces on the short end and the
long end, the cable could be curved and lengthened to control exactly the rate
of transfer of momentum between weight and payload.

------
edmundhuber
I'm very skeptical, of course I'm not as smart or as informed as many other
people so what I'm saying might not mean anything.

1) if the idea is to impart all of the kinetic energy needed to get into LEO
at once, on the ground, then you are talking ~17,000 MPH worth of KE (though
truly, more, because of loss to drag). There's a reason why max-q is an
important consideration in the design of space vehicles. The space shuttle
reaches max-q at 30K feet, where the density of air is 3x less than at sea
level. How do you design your vehicle so that it doesn't turn into dust when
it hits 1 ATM at 17,000+ MPH?

2) the centripetal force on the vehicle, prior to launch, will be enormous. So
in addition to not deforming and/or burning up the moment the vehicle hits the
air, the vehicle also needs to be built sturdily enough to not get crushed
while being accelerated.

I read Bad Blood a few weekends ago. Holmes hoodwinked investors who wanted to
believe that a fairy tale technology could exist, by never publishing or
otherwise allowing outside scrutiny of their technology. How is this company
different?

~~~
the8472
> So in addition to not deforming and/or burning up the moment the vehicle
> hits the air, the vehicle also needs to be built sturdily enough to not get
> crushed while being accelerated.

Since launch mass is less of a concern maybe they can just manufature the
satellites differently, e.g. filling the voids with a resin or oil which
distributes the forces uniformly.

------
binarymax
Years ago I backed the Slingatron [0] on Kickstarter, but sadly it was not
funded. At first I thought maybe SpinLaunch was a rebrand of HyperV, but that
is not the case and its an entirely different group of people. Either way, I'm
glad this is getting actual money behind it since it's a very interesting
solution, and I hope it "takes off" (sorry).

[0] [https://www.kickstarter.com/projects/391496725/the-
slingatro...](https://www.kickstarter.com/projects/391496725/the-slingatron-
building-a-railroad-to-space)

------
mrfusion
It’s surprising how many ways there are to get things into space. Everyone
seems to assume we’ve already considered all alternatives and rockets are all
we have.

Off the top of my head:

Providing laser power from the ground station

Giant rail gun

Launch fountain

Launch loop

Space elevator

Sky hook

This spin machine

~~~
rossjudson
How about "floating balloon launch loop"?

A giant torus that floats near the edge of the atmosphere. Spin it for more
lift, stability, and to throw things.

;)

~~~
crystalPalace
You beat me to it, I was just about to add balloons/rockoons.

------
jimbofisher1
This is just total lunacy. Have we reached peak VC yet? If not I have a
startup that is building a warp drive even though its totally theoretical and
the technology to build one is 100+ years away. Throw money at me please.

~~~
sharemywin
If it's built on blockchain, I'm in.

~~~
jimbofisher1
Its built on blockchain using state of the art Deep Learning. Our website is
pleasegivememoney.io and all of our founders dropped out of Stanford CS.

------
rdl
I’ve wanted to build a Gerald Bull style space cannon (but the more modern UW
RAMAC style) for a long time. Prototype would be $2-5mm, something small which
could actually put something decent into orbit around $50mm. I’ve heard there
is a group in SoCal which finally got funding to build it.

~~~
growlist
Would love to know more if you have a link about this group. For some reason
I'm fascinated by the space gun concept. Even if it were only used to launch
raw materials into space cheaply that could still be a huge boost to space
exploration.

------
beaconstudios
I wonder what the flight path would have to look like - I assume you wouldn't
be able to accelerate in a circle on the ground and then tilt upwards because
of the G force of the tilt. So you would either sling horizontally at a fairly
slight incline (taking advantage of the curvature of the earth, but imagine
keeping that flight path clear), have a slowly increasing ramp that would
probably have to be really long to manage the G force, or accelerate in a
vertically-oriented loop (which would have to be huge to cope with faster
speeds). I'm guessing the slow ramp is most practical.

Either way, there's some interesting info on the concept at
[https://en.wikipedia.org/wiki/Space_gun](https://en.wikipedia.org/wiki/Space_gun)
and
[https://en.wikipedia.org/wiki/Mass_driver](https://en.wikipedia.org/wiki/Mass_driver).

~~~
tlrobinson
If the radius of the ramp is the same as the loop wouldn’t it experience the
same acceleration once diverted to the ramp? (but in a different direction)

~~~
beaconstudios
I did the maths and if I'm right (I'm terrible at maths) then a loop would be
impractical for any reasonable G force anyway - the radius would have to be
over 100km for even 50gs. I'm guessing they'd need some kind of linear
acceleration, in which case they can just point upwards anyway.

------
dforrestwilson
Hadn’t occurred to me before but this article made me curious.

Every time that an object leaves our planet’s atmosphere we (apparently)
minutely change the earth’s orbit.

[https://space.stackexchange.com/questions/26733/does-
launchi...](https://space.stackexchange.com/questions/26733/does-launching-a-
device-into-orbit-change-earths-orbit)

~~~
astrodust
Every time you fart you minutely change the Earth's orbit.

~~~
ravar
No actually. The mass doesn't leave the earth.

~~~
TeMPOraL
The mass leaving the surface and entering orbit around Earth doesn't change
the location of the pair's center of mass.

------
ChuckMcM
I would love to see these guys succeed both because it would be something
truly novel, and because I think low cost access to space is going to be
critical moving forward.

But the physics of getting through the troposphere at 7 to 9 km/sec seem to be
really difficult to overcome.

------
lev99
There is a lot of published raw science on Electromagnetic Linear Motors, with
several feasibility studies on Earth to Orbit and Earth to Moon systems.

There are several challenges with building on that large, such as building
large capacitors, building a structure big enough, and dealing with something
that high energy. However, I think we are at a critical point where this might
become something we understand how to build. We use the fundamental technology
everyday in high speed rail, and we've learned a lot from constructing
projects like the LHC and Hyperloop. The Navy is planning on implemented these
motors for launch assist on the next generation of aircraft carriers.

------
shashanoid
THE LOGIN DOESNT WORK WTF [http://spinlaunch.com/](http://spinlaunch.com/)

------
piker
Will reaching max q at sea level limit how much energy they can put into the
projectile?

~~~
Maybestring
Drag being a factor of velocity squared means diminishing returns for
increasing launch velocity, but there's no hard limit.

------
zer0faith
Can someone ELI5 how this Space Catapult should "theoretical" work?

~~~
gnode
The article is very light on details, but I believe what's being proposed is
an evacuated tube with maglev propulsion, used to accelerate a rocket up to
5000mph (as stated in the article) while on the ground. The rocket is then
released, and travels until some altitude is reached, at which point engine
then starts and it continues to orbit. This results in a large fuel saving
over a conventional rocket.

[https://en.wikipedia.org/wiki/Mass_driver](https://en.wikipedia.org/wiki/Mass_driver)

The g-forces involved would be very high, well beyond lethal to a human, so
this would be for launching robust satellites, raw materials, or fuel cheaply
into space. They would still be substantially lower than those of a space gun
/ intercontinental artillery.

[https://en.wikipedia.org/wiki/Space_gun#Practical_attempts](https://en.wikipedia.org/wiki/Space_gun#Practical_attempts)

~~~
zer0faith
Would it be fair to say it is kinda like punkin chunkin?

[https://en.wikipedia.org/wiki/Pumpkin_chucking](https://en.wikipedia.org/wiki/Pumpkin_chucking)

~~~
gnode
Similar. I'd like to see a maglev (railgun) pumpkin chuck though.

------
trhway
Kind obvious solution when you loop the idea of long gun launch into a fast
spinning ferris wheel. Much easy and simpler power delivery. Centripetal
acceleration bites though.

------
Dowwie
Seems like a reasonable next step following impeachment.

------
carapace
I've been exploring large-scale structures built using the "Tensegrity"
concepts of Bucky Fuller and Ken Snelson. I'm pretty sure you can build
_really large_ structures using modern materials (e.g. kevlar and carbon
fiber.) Call it "giga-tech" (like nano-tech but scale up instead of down.)

One thing in particular that seems feasible is a large floating structure,
like a mile-high pyramid, placed on an ocean at the equator, and supporting a
launch structure.

I _think_ you can make a very large whip-like jointed spaceframe that acts
like a catapult to accelerate payloads.

By enclosing the outer surface with a membrane you can use solar energy to
evaporate water, then condense it at the top of the structure into holding
tanks. The mass of the water powers the whip like a trebuchet. (Or you can
extract electricity using the principle of Lord Kelvin's Thunderstorm.)

I'm pretty sure it would work. No advanced technology or concepts used at all.
I don't quite have the chops to do the back-of-envelope math though. Right now
I'm working on computer simulations (Finite Element Method.) I'm fortunate
that NASA has a program working on tensegrity robots for exploring the
surfaces of other planets, and they have released a tool that can simulate
tensegrity structures.

One other thing, in re: rockets and drag. I can't find a reference right now,
but _electrifying_ a rocket with a charge difference from the nose to the tail
can significantly reduce drag as the field accelerates the air itself.

