On Jan/31/2020 at 07:03, Jeff Findley wrote :
In article , says...

On Jan/30/2020 à 17:02, wrote :
See:

https://www.wired.com/story/inside-s...t-kept-secret/

How practical is this idea compared to conventional rocketry?

Totally impractical. Try travelling at a speed near orbital velocity low
in the atmosphere. It is hard enough to do so at 50 km altitude, doing
it low in the atmosphere is quite unlikely. If you launch at an altitude
of 7.5 km (that would be in Asia, you can't find such a mountain outside
Asia) the atmospheric pressure would be about 150 times higher than at
50 km.

My opinion is that this is a scam.

I wouldn't go so far as to say it's a complete scam, but it's certainly
a niche solution looking for a problem to solve. You're only going to
be able to launch payloads which can take *a lot* of Gs (i.e. crew
launch is right out, as well as most satellite launches). And when the
vehicle (supersonic projectile really) exits the launcher, you're going
to get one hell of a sonic boom in the area surrounding the facility, so
you can't really build a spin-launcher anywhere near people or animals
(so desert or remote island launch?). So, anything you launch will have
to be transported to a remote site to begin with! Not terribly
practical compared with other launch options.

So, what's left that's remotely practical to launch with this thing?
Bulk cargo and warheads. And even with bulk cargo, you're going to
either need a tug in LEO to get the payload to somewhere useful, or this
thing is going to be resupplying a LEO fuel depot or similar.

I don't think it has a launch rate high enough to be interesting for
launching warheads. They advertise a possible high launch rate,
something like a few launches per day, that is high for orbital rockets
but way too low for guns.


Alain Fournier