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Apply HN: Ram Accelerator Supergun Space Launch

27 pointsrdl15 comments

Idea: a cheap cannon-based space launch system

Who: Ryan Lackey <ryan.lackey@gmail.com>

Objective: to put satellites into LEO, materials into higher orbit, and do so at <$500/kg to LEO.

Stage: some research, no detailed plan, looking for expertise

Technology: A "Ram Accelerator" -- essentially a 10km long, 1m bore cannon, to be built in a remote location, ideally on a mountain near the equator (Ecuador? Ethiopia? Somalia?). 500 m/s chemical gun at the breach, projectile enters a tube 10km filled with ~10 different mixtures of natural gas and oxygen. Projectile is shaped like a ramjet core (cones), so it compresses/detonates fuel, causing constant acceleration. Leaves muzzle at 10 km/s. Hits atmosphere, massive boom. Projectile contains booster rocket and circularizing rocket.

Projectile peak G load is ~5-10k G, which is a non-issue for solid state/potted electronics. Deployables can be immersed in incompressible liquid fuel.

When: "Someday". I'm not an expert in aerospace/mechanical engineering, so I'd need to find solid cofounders, and would like to validate the idea more. It's been researched extensively at UW, Boeing, and other places over the past 15y. Production scale is a $50-100mm project. Subscale is maybe $5mm.

Fellowship product: Detailed computer simulation and answers to key questions (barrel erosion, payloads/capacities, costs, market)

Final Product: Probably a LEO satcom/sensing constellation, or delivered components to orbit, rather than launch services themselves, due to unique characteristics of launch platform.

Links for reference: http://ramaccelerator.org/home/ https://en.wikipedia.org/wiki/Ram_accelerator http://www.tbfg.org/papers/Ram%20Accelerator%20Technical%20Risks%20ISDC07.pdf

(I have full-time other things to do, but I wanted to write this up just to get feedback from people smarter than me.)

1) What timelines are you looking for a prototype device?

2) What are your rough upfront cost estimates for the timeline you are looking at? IS this cost based on building-from-scratch type of approach or buy off-the-shelf-components-and-repurpose kind of approach?

3) Which country are you looking at realistically? (Some of the countries you have outlined are battling big economic, political and piracy issues)

4) What container materials are looking at - considering they have to withstand massive G-forces plus friction heat (air or inner cannon surface) ?

1) ~6mo to recruit a team and agree on the broad plan. During that a combination of more comprehensive literature survey, meeting with the experts, investigating university research programs solving key problems which could be funded, etc. Concrete deliverables around a well communicated-to-public plan, simulation, etc., both of the launcher and application/payload.

Probably (to be altered): ~1y to recreate the subscale systems used at various universities, set up basic capabilities, etc. Obviously faster if I can just work with UW or one of the other groups. Another...2-3y to build the first subscale prototype capable of putting 1 gram into space (without circularization), but with a rocket second (and maybe third) stage.

Parallel development of the ~1m scale projectile, boost rocket, circularizing rocket.

Parallel development of LEO satcom payloads -- initial payloads inert, then maybe some remote sensing/beacon/etc. payloads, and suboptimal but research/commercial satellites. For a full LEO 1-3Mbps to the handheld terminal constellation, need frequency licensing, a lot of consumer electronics and specialized electronics, etc.; it used to be a 5-10y project even given standard satellites -- it probably could be done in 2-4y today. One huge advantage of low-lifespan LEO: you can rev the satellite design every month.

(Another option is doing the LEO satcom stuff in parallel using a conventional launcher at lower density.)

The full production scale system to orbit is probably ~5y after the first subscale to space.

(My real problem here is I have another much more practical startup which is unrelated, and in an area where I'm an expert, unlike this, where I'm merely interested. I'd rather do that, make money from it, then build this when I can at least contribute 3-5mm to it myself. So that pushes all of this out at least 3y and hopefully 5-10y. If I suddenly have a lot of cash, I'd probably be able to pay to have some of the earlier engineering work done on this, and if I had the right team, could probably just be an investor/boardmember.)

3) Kenya is probably the win (definitely Horn of Africa or South America; nowhere else is economically viable). Ethiopia also works. It would be done with full US ITAR compliance -- physical custody of the site, local construction and education, but no weapons proliferation. Ethiopia and Kenya are pretty solid US allies. I'd expect there would be a Bn or greater of host nation military/police assigned for outer security.

4) Ablative coatings, carbon/carbon structure. Only getting cheaper/better. I don't know much about the state of the art here, but it has been feasible for decades using older tech.

Thanks for the detailed reply.

This concept has been around for a very long time. The first question I would ask is, if it's feasible and superior to rockets in some way, why hasn't it been done yet?

1) Hasn't REALLY been proven (the chemical and light gas guns are farther along; the ramac part not as much).

2) Until SpaceX, the idea of entrepreneurial space didn't exist.

3) Payload uniqueness -- this never will work for human passengers, so NASA won't fund it. The value of 1 x 100kg into LEO every hour every day for years on each launcher is not yet established.

What sort of simulation would you do that has not been done at Boeing, UW, etc.?

I am an aerospace/mechanical engineer. I think that the manufacturing aspects of this would be far more difficult to overcome than the mathematics of proving the idea as viable. In other words, it works in theory but in reality you can't make a tube with smooth enough connection points etc. Will you look at that too?

If you get this and are looking for minions let me know.

Mainly interested in openly vetting the launcher itself, but also doing reasonable system planning for the LEO satcom/sensing portion (which has evolved a lot over the past years). I have some experience in satcom myself.

(frequency access is probably the main issue there)

I'd suspect that the hardpart wouldn't be finding payloads that can surived the G forces but building a rocket that that can. If the rocket could be stored in in-compressible fluid,then the mechanism to eject the rocket from fluid would need to be safe against super high g forces.

Mostly a solved problem. 155mm artillery rounds with full computer guidance and rocket-assist exist, and they get 50k G. (We can put nuclear bombs inside 203mm artillery, which is maybe 30k G.)

The bigger the bore, the lower the peak acceleration, and RAMAC is inherently a "long shove" vs. a specific impulse at the breach.

It absolutely rules out passengers, but doesn't really seem to be a big problem for components.

The much bigger problems are sound/ablation at the muzzle (hitting the atmosphere suddenly at 10km/s...), and barrel life/erosion (big battleship guns got...150 round lifespan. Barrel erosion is related to velocity. The breach of this will not have much difficulty, but the muzzle end probably won't do well. OTOH it's not rifled or otherwise close-fit, and could have "wipers" which are themselves ablative/disposable. Since there's a rocket/guidance package, it doesn't need to be as low-tolerance as an old battleship gun.

(System has been prototyped by Bull using 16" surplus battleship guns in Barbados)

Can you aim the cannon? If not, you would be limited in the orbits that you could access without some sort of on orbit propulsion. Is that true?

You can't aim the cannon itself; you can adjust trajectory using the second-stage rocket. It's essentially just a launcher for one set of orbits, though. The actual launcher cost is probably not that significant ($100mm?) once you've built one; you can build 10 in different locations/orbits.

For the thing I want to do, one launch position works (I think) for LEO comsat constellation (hundreds/thousands of <2y lifespan satellites).

I am deeply skeptical at the notion that electronics payloads can withstand 5k to 10k g's of loading. A one gram component would experience 100 newtons of loading. That's over 20 pounds of force exerted on something the mass of a paperclip.

These aren't your nice, typical static loads, either. Dynamic loading tends to not play nicely with brittle materials, so solar panels will fracture. I would be extremely concerned about the integrity of highly chemically reactive batteries when what's normally a small five pound pack weighs as much as a Bradley fighting vehicle.

My questions is, am I getting this wrong? Are you able to cite sources that say this kind of g loading isn't an issue?

Addressed comprehensively in http://www.tbfg.org/papers/Ram%20Accelerator%20Technical%20R... (pages 12-14).

The load on a dropped consumer electronics device falling onto a hard surface at deceleration is actually pretty close.

It actually isn't even 10k G for a 1m diameter ram accelerator; that was for a light gas gun of smaller diameter and length). More like 2k

Won't this greatly harm(financially) SpaceX and other rocket companies, and thus prevent further effort on settling mars ?

There are some payloads which work well in a launcher like this -- bulk materials/fuels, tiny satellites for LEO. Other things will never work -- big satellites, humans.

ULA = extortionists. SpaceX should do fine. (Also, if Elon wanted to build this, I'd be perfectly happy to work with him; I just want the 100000th ticket to Mars.)

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