# SpinLaunch kinetic throw to orbit

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#### bmcj

##### Well-Known Member
Anyone else spot this news?

#### Dana

##### Super Moderator
Staff member
How much of the payload is heat shield? And the payload only has to be able to take 10,000 g!

#### bmcj

##### Well-Known Member
How much of the payload is heat shield? And the payload only has to be able to take 10,000 g!
Yeah, heat shield can be done, but that 10,000 g seems to me to ba a major hurdle. I doubt that any useful satellite could survive the g load.

#### DaveD

##### Well-Known Member
Heatshield that can withstand piercing the vacuum containment membrane thing at 5000mph!

The ground level sonic boom must be fun!

#### trimtab

##### Well-Known Member
Lessee...450rpm, 33m diameter....

3734 g's advertised. M2.26. 777 m/s.

It was done at 20% power, whatever that means.

The article claims "supersonic", which implies an RPM of around at least 200 rpm. It claims an altitude of at least 10,000 feet. I'm a vacuum, 250 m/s is required. With atmosphere, a lot more speed is required. A lot lot more at the 35 degree launch angle.

I wonder what the sonic boom acoustics are like.

#### Marc Zeitlin

##### Exalted Grand Poobah
How much of the payload is heat shield? And the payload only has to be able to take 10,000 g!
When I was in college (back in the 1830's, if I can remember back that far), one of the things my thesis advisor (Henry Kolm - the inventor of the maglev trains and the electric catapults that are now being installed in aircraft carriers, the prototype of which I did my MS thesis on a part of) was looking at was using an electric rail-gun to launch stuff into orbit up the side of large mountains. We figured that the actual payload to orbit, after ablative heat shield, was actually pretty close to 90 - 95%, and that was on something that had no rockets to accelerate it to orbital velocity. So for this thing, only going to 5K mph to eliminate the first rocket stage, I'd say that the heat shield will be a minimal part of the weight of the payload.

10K g's would be a major problem for things like space telescopes, but just to throw raw materials or solid state electronics into orbit, it actually isn't all that much of an issue.

#### Pops

##### Well-Known Member
Log Member
maglev trains. I was playing with two magnets shaped like life savers on a dowel rod when I was about 8-10 years old and had the idea for maglev trains. I'm sure I wasn't the first. Also propelled by electro-magnets switched on in front of the train. All running in a vacuum tubes under the ground for very high speeds.

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#### Hot Wings

##### Grumpy Cynic
Log Member
How do they re-balance after payload release

#### trimtab

##### Well-Known Member
That is the magic question. I can think of a few schemes. I have not seen any info on how they do it though.

##### Well-Known Member
There's actually 3 distinct sets of G forces.
1. Lateral - during spinup. Many many g.
2. Longitudinal negative - after release, as it's being slowed by air drag.
2. Longitudinal positive - once the second stage lights to take it to orbit.

#### bmcj

##### Well-Known Member
How do they re-balance after payload release
I was wondering the same. One thought I had was to mount the arm on an eccentric hub so that the pivot center of rotation can be shifted toward rhe payload end after release.

Another way would be to have a cylindrical counterweight weighted more to the outside edge, then spin that cylinder to move the heavier side in toward the center of the arm.

… or how about a large dynamic balancer?

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#### Aesquire

##### Well-Known Member
Watch a trebuchet video. The sling release puts huge forces into the frame. There was a tv program ( NOVA, see War Wolf link below ) where they built a full size treb' and explained with models 2 different ways the medieval engineers compensated and used the release load change to throw harder. That's a really incomplete gloss on the subject, sorry. I need diagrams with arrows and hand gestures... Or models, or animation, to properly explain the way the energy moves. ( watch the Nova episode )

And that's with an arm and counterweight that only goes about 200+ degrees rotation, no combustion or steam or chemical energy boost. Scary power, huge stresses. See note 1

A full circle catapult is terrifying to contemplate. See pumpkin chucker competitions!

I'd love details on the equal & opposite reaction paths and how they keep it all together.

Btw, I give credit to Robert Heinlein for promoting rail launch multistage rocket launch. He didn't invent it, but it figured prominently in "The Man Who Sold The Moon". A rail up Pikes Peak and details of Staged rocketry, parachute recovery, including mention of the need to evacuate at great expense the possible impact zone for the lower stages. You know it's really Hard Real Science when insurance is a factor as much as fuel chemistry.

( hopefully unnecessary plug for the master of Hard Science Fiction and his work. Just read some! )

Note 1.

Some years back the Engineering dept. And the Medieval Club at Alfred University got together and built a classic trebuchet of the swinging basket type broadly based on King Edward 1's War Wolf.

The engineering students did the math. The Club and friends built the monster. ( I helped a tiny bit ) They had a multi -ton counterweight, a "basket" (half) filled with rocks. It happily tossed big watermelon sized rocks 300 yards and this resulted in bureaucratic comedy. We built this thing in a public park along the canal/river front. Big underused space. The town was happy to have a college experiment and possible tourist attraction. Until it worked. The town was aghast that a fully functional engine of mass destruction circa 1300 was sitting there as an attractive nuisance!

We did get to practice with it before they demanded we chain it up so the town kids wouldn't lay siege to town hall. It got sold to a Ren Fair to get rid of it. I highly recommend watching one in person, it's a great physics in action lesson.

The final funny was the heavy equipment crew with crane and trailer that came to pick it up. They had a serious problem lifting the Big beams even with our head builder to advise on it's construction. At one point as they waited for more timbers to be brought to keep the crane from tipping, the heavy equipment crew chief was puzzling aloud how we built it without tearing up the park? He freaked out when we explained we did it Olde School, as they did in the 11th and 12th centuries, with an A frame of tree trunks, lots of rope, and lots of organized people pulling on them.

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#### galapoola

##### Well-Known Member
In the spin up one would assume the rotating mass needs to be in very fine balance. On launch that balance would be removed leaving said rotating mass waaaaay out of balance. That would put a huge stress on the launcher. Wonder how they plan to overcome that?

#### mquinn

##### Member
I am pretty certain the original ercoupe was designed to launch similar to this as to minimize runway length to take off... Basically like the old u-control model planes - but when got up to rotational speed the pilot would release the cable... (like the old airports that had no "heading" just a big round field that you could always takeoff into the wind (and land that way too)...

#### rv7charlie

##### Well-Known Member
Btw, I give credit to Robert Heinlein for promoting rail launch multistage rocket launch. He didn't invent it, but it figured prominently in "The Man Who Sold The Moon".
And for even more developed 'other uses', see his The Moon is a Harsh Mistress. Rail gun launchers play a minor but significant part in the book, which has a *lot* of additional Hard Science Fiction (in addition to having a great story line).

While you guys were building flying models, I was wasting my time reading Heinlein, Asimov, Clark, etc.

#### trimtab

##### Well-Known Member
There are a number of methods including release of a counterweight (liquid or gas), a sudden shift of a weight that slides outward in a timed fashion to be arrested at the release, a large dynamic balancer to delay the offset until an offset is made, or simply the provision to accommodate the forces. If there was always an imbalance equal to half the force of the launch vehicle, then the lost release would simply be a reversal that might be accommodated with a dynamic balancer. Hydrodynamic bearings carry a lot more weight than this all the time. The speed is a bit unique, but the characteristics of the fluid would be different, that's all. It looks like a really fun project. If you can deal with the structural resonances through careful pendulum design to prevent excitation from the mount, and careful mount construction to passively damp way below the other frequencies, a dynamic balancer in the counterweight and perhaps another at the payload might be able to significantly damp the system. Compensating mass might be emplaced (liquid or solid) rapidly enough to prevent any lower Q gain from amplifying to problematic levels.

#### Wanttaja

##### Well-Known Member
10K g's would be a major problem for things like space telescopes, but just to throw raw materials or solid state electronics into orbit, it actually isn't all that much of an issue.
Even as far back as WWII they were putting radar sets into anti-aircraft shells (proximity fuzes). One thing I read said they withstood 20K Gs.

Ron Wanttaja

#### BJC

##### Well-Known Member
There are a number of methods including release of a counterweight (liquid or gas), a sudden shift of a weight that slides outward in a timed fashion to be arrested at the release
I wonder where they would end up.

BJC

#### wsimpso1

##### Super Moderator
Staff member
Log Member
How much of the payload is heat shield? And the payload only has to be able to take 10,000 g!
I will leave the heatshield question to others, but electronics that can stand a gun launch have been around since WWII.

The US military deployed and used proximity fused projectiles for artillery against ground forces and as anti-aircraft fire. They have a battery, RF circuitry, antennas, etc and are widely deployed down to 20mm guns for air-to-air and ground-to-air. Max accel during projectile launch is in the 10,000 g range. There are also a variety of laser guided and GPS guided artillery shells, and they generally have to stand on the order of 10,000 g during artillery launch.

The simplest technique to stand launch is potting the electronics. When flight is only measured in seconds, who cares about cooling the circuits? For a satellite that would need months or years of operation time, they would have to get fancier about things, but it is all in range.

Yes, there will be weight consequences for a spin launch satellite over a rocket launched one that only has to be built to stand truck transport, handling, then rocket launch.

One of the things that I just can not let stand is the zero-emissions claim. The transportation, construction equipment, steel, cement, aggregates, sealers, electric motors, the tether, etc, to build such a huge vacuum chamber and centerfuge will take plenty of petrochemicals. Then to run it, the electricity has to come from a substantial power plant. Maybe you could run it with solar cells and wind power, while cutting other local electricity during the pump down and spin up. You would only need to squelch local power for a couple hours per launch. Maybe a local power system dedicated to the launch facility would make sense...

Billski

#### D Hillberg

##### Well-Known Member
Carnival ride gone NASA