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A Space Cannon That Might Actually Work
Unequivocal writes "Chalk another one up to Jules Verne. Physicist John Hunter is proposing a space cannon with a new design idea: it's mostly submerged. 'Many engineers have toyed with the [space cannon] concept, but nobody has came up with an actual project that may work. Hunter's idea is simple: Build a cannon near the equator, submerged in the ocean, hooked to a floating rig ... A system like this will cut launch costs from $5,000 per pound to only $250 per pound. It won't launch people into space because of the excessive acceleration, but those guys at the ISS can use it to order pizza and real ice cream.' Though it won't work on people, with launch costs that low, who cares?"
The last guy with a plan to build a super-cannon (a Canadian named Bull) did some work for Saddam Hussein. The Israelis didn't like that much, so they murdered him.
I've calculated my velocity with such exquisite precision that I have no idea where I am.
Here is an interesting "tech talk" at Google where John Hunter explains the workings of the cannon:
http://www.youtube.com/watch?v=1IXYsDdPvbo
You could shoot a rocket from a cannon, meaning you'd need less fuel (meaning a smaller fuel tank, meaning even less fuel) to get it up to speed.
I'd rather you rationally disagree than irrationally agree.
Wow, that article is horrid. They don't even mention Hunter's startup company: Quicklaunch. On that page you'll find his Google Tech Talk on the subject which answers many of the questions that people are asking here.
How we know is more important than what we know.
10 mins into the Google Tech Talk he gives a slide with the amortization cost per lb. About 20 mins in, he breaks the project up into phases and costs needed to complete each phase.
http://www.youtube.com/watch?v=1IXYsDdPvbo
It's worth watching the video for more info on G-Force hardening, Hydrogen re-capture, per-lb cost and project milestone/costs.
-Malakai
A Dragon Lives in my Garage
You have to shoot a rocket from a canon anyway. If you don't, you just end up shooting yourself in the back. You can't put something in orbit solely with a gun.
Also Russian tanks starting from T-64B can shoot missiles from their cannons.
"It's such a fine line between stupid and clever" -- David St. Hubbins, Spinal Tap
Do you realize just how far away the moon is from Earth?
This to-scale image should give you an idea of just how ridiculous this idea is.
http://en.wikipedia.org/wiki/File:Speed_of_light_from_Earth_to_Moon.gif
Keep watching the Tech Talk, he 'rails' on rail guns.
Basically, world record for rail gun right now is 5.5 km/s, after 200 million being spent on it. World record for Hydrogen gas gun is 11.2 at a fraction of the cost. Energy storage costs and other factors kill using electric for so large of a project.
He spends quite a bit of time discussing it when he goes over the history of rocket/guns, about 25mins in I think.
Also, he was paid by the navy to make gauss guns and rail guns, he just doesn't seem them as the right tool for this.
-Malakai
A Dragon Lives in my Garage
The man doesn't seem like a quack to me: http://en.wikipedia.org/wiki/Project_HARP
Also, the only mentioned test wasn't exactly a failure what I see; it just revealed some problems, which is understandable with such project.
(and y'know, I was aiming more at Funny...)
One that hath name thou can not otter
The idea is to get something into orbit, not shoot it away from the planet. To go into orbit around Earth you have to fire the projectile with LESS than escape velocity.
If you just fire a projectile, with no rocket, into a non-escape orbit, the only possible orbits are those that intersect the firing point. That is, the projectile will go all the way around the planet and hit you from behind. You've just shot yourself in the back in the most dramatic way possible.
I think you dropped a zero or two somewhere in your calculation. Escape velocity from the Earth's surface (neglecting air resistance) is 7 mi/s. 7 mi/s * 60 * 60 = 25000 mph. Escape velocity is about twice the speed they're aiming for, plus you're going to burn a decent amount of that speed off in the atmosphere. Emphasis on "burn." Which makes perfect sense since they're talking about delivering payloads to Earth orbit, not to some solar orbit, which wouldn't be very useful.
Even if a 1.5 light second long cable were feasible you'd still have to deal with the fact that, as far as I understand, the anchor would have to be in geosynchronous orbit. Since the Moon isn't in geosynchronous orbit, the surface moves relative to the Moon you'd end up winding the cable around the planet.
A bit of math here. Escape velocity on earth is 10.735Km/sec, Acceleration at 6G = 9.8*6=58.8 M/Sec^2. 10735/58.8 = 182.5 Second to reach escape velocity
Distance travelled during that that time 10.735*182.5/2 = 979 Km. Basically to accelerate a body to escape velocity with a steady 6G acceleration would require a tube almost 1000 KM long. Even popping up to 10G the tube would be 585Km long.
These calculations do not even take into consideration deceleration due to drag.
By the way, escape velocity is approximately Mach 31. Building a 1000 pound object that can go through the atmosphere at that speed would be difficult. Cannon rounds from an M1 only go Mach 5.
The original Popular Science article is a much better read and includes additional detail, including the fact that the projectile will experience 5,000G forces. Definitely not for human passengers.
'The tyrant will always find pretext for his tyranny.' - Aesop's Fables
Sorry, but I don't see the benefit of floating the cannon in the ocean.
1. You can aim it. This is a big fucking deal
2. Weight is not a factor. You can build your cannon as heavy and as strong as you please.
3. You don't have to worry about safety because any failures will happen underwater and away from land. This is also a big fucking deal