There is a reason fish don't swim in a circle to build up speed to jump out of the water, because their own wake would stop them cold.
I wonder if someone could do a quick CFD of a payload travelling in a 7.6km/s at sea level is in the 'high hypersonic' regime (> MACH 10 closer to MACH 25) The energy you are dumping into the air at that point is going to create a pretty impressive flame front by itself. This is perhaps the coolest things about the really high speed videos of the Navy railgun project.
A plasma bearing.
You have to admire their chutzpah.
Super-interesting concept, and the people at HyperV Technologies Corp seem to know what they're talking about, so I am excited about this. For example, their other KS project—the Plasma Jet Electric Thrusters for Spacecraft[^1]—was successful both in funding and delivering what was promised.
Also, you gotta love their pretty low-key / somewhat amateur'ish videos. ;)
Everyone grows up. Except physicists. Physicists are special.
Or else, how do you explain a grown man sitting in front of a leynhurst generator for an entire noon just turning the wheel and marveling at the discharge?
The kickstarter aesthetic
I disagree. Most KS videos I watched were very upbeat/chippy/hipster'ish/enthusiastic pieces of semi-professional ad/film making. The HyperV videos, not so much. They look like transfers from a VHS camcorder. :)
Wikipedia helpfully informs me that this is 3-4 times the rating of the electronics used in artillery fuzes.
Radial forces on the launch platform itself are more of a concern. You have to stop it from tearing itself apart while it overcomes friction/drag and reaches escape velocity.
a = v^2/r
so let's go with 1km/sec and a diameter of 5m. a = 1,000 x 1,000 / 2.5 = 400,000 m/s^2 or roughly 40,000 g
Now let's assume that it's a 1/4lb weight as described or 0.1kg.
F = m x a = 0.1 x 400,000 = 40,000 newtons.
Next let's assume that the piece of metal is steel and roughly cubic. It's density is around 8g/cm^3 (http://hypertextbook.com/facts/2004/KarenSutherland.shtml).
Mass = density x volume => volume = mass / density = 100g / 8g/cm^3 = 12cm^3
cube root(12) ~= 2.3 so we've got a cube with faces around 2.3cm on a side.
They've said that they're going to encase it in plastic so let's neglect the strength of the plastic and call it 2x the size of the cube. That brings this to 5cm x 5cm.
Now let's translate that into pressure.
P = F / a = 40,000 / (.05 x .05) = 16 MPa
The tensile yield strength for a regular, boring steel (A36) is 250MPa and the ultimate tensile strength (the max it can hold prior to breaking but after deforming) is 400MPa so this is fine for now.
At 2km/sec you get 64MPa needed and at 7km/sec you need 784MPa all of which are within the realm of possible but rapidly heading towards the limits of material strength.
The 784MPa number would go down if you made the diameter bigger, too.
Ultimately they aren't building a thing which will disintegrate the slug (my initial thought) but it's going to have to be extremely well engineered and precisely made for balance in order to ensure that it doesn't tear itself apart. The technical combination of a steel rolling mill and a swiss watch. And due to balance issues definitely harder from a technical perspective than even the really tough portions of a rocket.
EDIT: didn't realize that "*" did formatting so I fixed it.
EDIT2: Screwed up on the calcs, assumed 10,000m/sec instead of 1,000/msec. Fixing those.
Of course you burn up because you are moving so fast. But imagine that you put a big tube around the planet and pulled a vacuum in that tube. Then you could be in orbit just off the ground, how fun would that be?
Just as impractical as this idea however as you'd have to hold the vacuum in a very very long tube.
a = v^2 / r = 15,000 x 15,000 / 500 = 450,000 m/sec^2 or 45,000g. It's on the same order of magnitude as the previous calcs.
That's obviously also a big engineering challenge because it's freaking HUGE, especially for the precision required.
The really great thing about going super-super fast is that at 15km/sec you're in space in ~10 seconds. Obviously you're going to start scrubbing speed really fast since drag is proportional to velocity squared. But you can evacuate the whole launch assembly and put some kind of an explosively opened door at the exit point and maintain your speed up until the last second.
I don't think it's practical in any manner but I think such brute-forcing stream of projectiles out of atmosphere by literally punching hole in it might be nice to look at.
When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction to that of the first body.
If you plan to generate acceleration using mechanical force like the reference design, you'd need a massive counterweight. An equal and opposite energy would be transferred to the counterweight, so you need a lot of mass, which would require an even more massive dirigible. You also need somewhere to dissipate that energy. In the reference design, the Earth is used as the counterweight.
Alternatively, you could generate the circular motion using something like a rocket engine, in which case you might as well just use a rocket for linear acceleration and ditch the gyration mechanism.
indeed. tho, we should also note that we are looking at a weakest link thing. can that one bolt sustain that much pressure? or maybe that one weld? or any of the concrete parts that attach to the earth itself?
Also, you'd durability as well as raw strength of materials will come in here since they'll be trying to use the thing repeatedly.
I realize building it in space would be a good bit harder than on the ground. I'm just in wouldn't-it-be-cool land.
Is Mike already lurking in some massive instance?!
If you want to throw something that heavy, you'll have a much easier time using explosives to do it -- and we've been able to do that for quite a long time now (multi-ton shells were fired in WWI).
I really like the outside-of-the-box approach and idea, it will be interesting to see if $250,000 is enough to build something of this magnitude which will need to be tested and tested and then tested 100 more times before you could even attempt to try it in the real world.
Also really interesting references to HARP in this thread: http://en.wikipedia.org/wiki/Super_High_Altitude_Research_Pr...
This general idea was the best I could find. Put the mechanics and fuel for the vast majority of orbital insertion inside some ground-based system, instead of trying to carry it. Impossible to use with humans, but for lots of other stuff like supplies, more fuel, habitats, etc -- should work fine. At least as far as I could tell. It's much more feasible than a Space Elevator, and no new tech needs to be invented.
Having said that, I'm not so sure this is going to work in KickStarter format. Sure, build a bigger laboratory model, but to make this really work it's going to need a lot of cash.
I'll suck on the -2 Karma for a while...