To be fair, it’s only meant to throw stuff to the point second stage rockets normally fire. Only 10000g….no problem, right?
Rail guns seem much more reasonable IMO. So does launching from a mountain top to avoid air resistance.

I was thinking the same thing.
But I do agree with him that it would be great on the Moon.

Using a mountainside might help with structural integrity, but it's not likely to give much air resistance advantage if I'm reading the math correctly. The 5 highest peaks in the US are all in Alaska and and range from just under 5km to just over 6km. Commercial jets using air resistance/density for lift fly at about 10km and even at 38km aerodynamic lift still carries 98% of the weight of the plane (https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line)

Air density is halved at 5km compared to sea level, but air resistance doesn't diminish as quickly (due to it being multiplied by velocity squared and drag coefficient), and only becomes irrelevant (for short-term purposes) around 100km at the Karman Line.

If we had a 5km peak in Florida, the lack of logistical costs might make the benefits worth it, and if we could build on one of Equador's 5km peaks, then there's the further advantage of equatorial location for optimal rotational advantage (part of the reason we launch from South Florida)

I’m thinking Mt Chimborazo in Ecuador…at over 20000 ft, it’s peak it the farthest from the center of the earth (while not being the highest above sea level thanks to the equatorial bulge).
Sure, it doesn’t remove air resistance or friction, but halving it, even cutting it by 1/3 is a massive leap in efficiency and negates much of the extreme engineering and materials needed to overcome the friction….plus, as you mentioned, there’s the rotational speed advantage from launching on the equator vs Florida.
Also, while extremely minor, there’s also a slight reduction in gravitational pull at those heights. A joule saved is a joule earned!

At those g forces, with few exceptions, it seems it would be useless to launch most satellites, and it’s definitely not for live cargo.
It would be great on the moon….as a super weapon to blackmail earth with. It could launch all the rocks the Moon Master desires at any earth target….like a moon mortar with unlimited ammo.

Yeah, 20000ft is roughly 6km. The air density is about 1/2 but from what I can determine that doesn't equal 1/2 air resistance, but something more like 90-95% air resistance of sea level.

Having said that, I haven't studied aerospace engineering, so I might be getting the details wrong.

There are definitely some minor advantages to building on a mountainside, but I don't think they outweigh logistical difficulties under normal circumstances.

The idea has a good bit of scifi (and probably scientific) history behind it though. I believe Heinlein used a railgun cargo launcher from the moon in Moon is a Harsh Mistress and a mountainside sled rocket in one of his earlier books.

Project Rho is a great resource for hard scifi and rocketry research for writers. http://www.projectrho.com/public_html/rocket/surfaceorbit.php is the link to a page that discusses maglev, railguns and rocketsleds.

*related=https://videosift.com/video/SpinLaunch-Engineering-Doc-Throwing-Satellites-into-Space

SpinLaunch Engineering Doc - Throwing Satellites into Space? has been added as a related post - related requested by eric3579.