[beervirus]

“The reason it's hard to get to orbit isn't that space is high up. It's hard to get to orbit because you have to go so fast.”

https://what-if.xkcd.com/58/

Sounds like this solves the easy part (getting to high altitude), but makes the hard part (getting to orbital velocity) even harder.

[CGamesPlay]

I think you're imagining that the rocket is fired directly vertically and peaks at some altitude, when the rocket ignite to "make it go fast". Instead, imagine the flings the rocket at a 45 degree angle so when it peaks in altitude it's already going quite fast. As other commentators in this thread point out, it's really an alternative for the primary stage rocket booster part, which doesn't just shoot a rocket straight up vertically.

[mlindner]

Except they're completely inverting the rocket. The rocket goes slow in the lower atmosphere where the forces are lower. This allows them to lose much less energy in the lower atmosphere from drag.

If they could just launch at 45 degrees to get to orbit the rockets would do that too, but no they don't. They go straight up at first because the drag is such a huge penalty to the performance.

If they actually build this thing, the most efficient way to launch is to launch it almost straight up at 90 degrees so they lose the least energy. However the hardest part is going to be immediately after exiting this thing where they hit the atmosphere going mach 6-7 and instantly turn into a glowing ball of plasma, which is what happens if you try to move that fast at sea level.

Drag forces increase with the square of the velocity and linearly with fluid density. The instant it leaves the cannon it will feel like it's hitting a brick wall.

[beervirus]

That would just cause even more problems with air resistance. We've flown at 5,000 miles per hour before, but nowhere near ground level.

This thing is going to tear itself apart as soon as it leaves the centrifuge.

[unnouinceput]

The image on the site says 35 degree angle.

[spicybright]

I'm still scratching my head thinking of how much force will be crushing the rocket and satellite for an hour. I know space stuff needs to be super durable, but surely the G's it'll experience over an hour will be more grueling than a traditional rocket, no?

[h2odragon]

> "At this point the spacecraft will be subjected to a peak force 10,000 times greater than Earth's gravity, something opponents believe will seriously affect its structural integrity and the safety of its complex electronics."

Centrifugal projectile weapons scale up poorly and have issues even at BB gun scale. Envisioning what happens with a 200lb projectile; leave aside the laughable velocities they're talking, and I want to be well distanced from these people when they power shit up.

I think this is a device for separating investors from money.

[pengaru]

I just assumed they fully expect to pivot into the defense industry.

[jasonwatkinspdx]

This isn't very appealing to defense either, due to the slow spin up.

[pengaru]

This isn't my area of expertise, but judging from some of the extreme physics they're dealing with I'm assuming they're solving problems with potentially lucrative military applications.

[jasonwatkinspdx]

They aren't solving anything, and no, there's no potentially lucrative military applications. This is just an investor scam. Dunno if the founders are true believers it or not, but this thing has 0% chance of producing anything interesting.

[TeMPOraL]

Hypersonic anti-ship missiles are a hot topic these days, maybe this is related.

[bfuclusion]

To get a rough idea of the numbers if this was a rail gun and accelerating linearly: 1G is 32 feet/second 32 feet /second is ~22 mph They're accelerating to 5000mph so they need to crush things at 1G for ~230 second or just under 4 minutes.

If I understand correctly, this would hold for angular acceleration too, since they'd just release at some point. Can someone correct me if I'm wrong?

[jseutter]

You're probably correct, but there is more.

Take a 200 pound payload, add some rocket to it, let's say 10x the weight to be generous, then spin it in a circle 200 feet in diameter. You're looking at 18 thousand tons of force spinning it at 5000mph. So you're spinning 4 navy destroyers worth of force in a circle, which means you need a latch mechanism that can not only hold that much force, but release it at the exact moment to exit the biggest vacuum chamber ever created through a door that just opened at the right time, generating a mach 6+ shock wave at about 0 meters distance from the door and somehow not destroying it in the process. I don't know that it is impossible, but it is highly improbable. They'd probably have a burst disk rather than a door, because that would let you use the capsule as a bullet to penetrate the exit.

In the article they mention the payload experiencing 10000g, so they must be planning on a circle greater than 200 feet in diameter. I can't find numbers on existing satellites, but I remember reading that rockets typically top out at 6g acceleration and figure on a 10x momentary acceleration due to vibration. To tolerate 10000g the payload being launched will need to be built like a tank, rather than the relatively light current designs. To ease that requirement you could submerge the payload in liquid, but that would decrease your usable payload accordingly.

It would be impressive if they could actually pull it off. I think it would be useful for limited applications. I have watched science fiction shows where mass accelerators could basically nuke planets without radioactive fallout. Maybe this would be something similar.

[inetsee]

Having read "The Moon is a Harsh Mistress" a looong time ago, I have sometimes wondered why no one has ever tried to use rail guns as launch mechanisms. I vaguely remember from not so long ago that one of the criticisms was that the acceleration forces would crush any fragile parts like electronics, but is it still true that electronics can't be hardened to survive the acceleration forces? Are there other problems that make the idea of rail gun launchers simply impossible?

[beervirus]

A rail gun would work from the moon, where there's no atmosphere. On earth, the projectile would attain its highest velocity (right as it leaves the rail gun) in the thickest part of the atmosphere (at ground level).

And just for a sense of scale, escape velocity from earth's surface--assuming no atmosphere at all--is 25,000 miles per hour. The projectile is going to tear itself apart in atmosphere at those speeds.

[dboreham]

Main problem is to avoid being assassinated by Mossad.