Hypersonic space cannon promises 10 minutes from ground to orbit | Hacker News Reader

Hypersonic space cannon promises 10 minutes from ground to orbit

newatlas.com

18 pointsclouddrover14 comments

Life imitating Jules Vernes http://www.astronautix.com/j/julesvernemoongun.html

I mean, I am all for new launch tech but it currently already only takes ~10 mins from launch to orbit. That orbit just might not be very useful, which is a problem you will basically always have.

For context, this is fairly old - 40 to 60 years - technology:

https://en.wikipedia.org/wiki/Supergun_affair

https://en.wikipedia.org/wiki/Gerald_Bull

https://en.wikipedia.org/wiki/Project_Babylon

eqterty43, If I may add;

Railgun : https://en.wikipedia.org/wiki/Railgun

>A railgun is a linear motor device,

  typically designed as a weapon, that uses electromagnetic force to launch high velocity projectiles.<*

Also see;
Pentagon to build nuclear micro-reactor to power far-flung-bases : https://www.militarytimes.com/news/your-military/2022/04/15/...
--

Edit: Add; Scramjet : https://en.wikipedia.org/wiki/Scramjet

Love that this is basically a huge 'potato gun'.

The most loved part of the most advanced potato gun would be the ultra-sonic “THUMP-WHOOSH——BOOM-BOOM!”

What about (low orbit) orbital platforms? Powerful maser can strike almost everything instantly. They can even launch kinetic/chemical warheads faster than a ground launch site. With today automatic LEO transporters, such platforms can be restocked periodically.

I expect that the big issue with using a cannon to launch things into space is that the small payload must be resistant to this sort of extreme acceleration.

Extreme acceleration and extreme heat from extreme velocity in the lower atmosphere.

Problems that could be solved but at what cost? The marketing for this is the reduced cost --- which may or may not hold up in practical terms with real satellites that are usually more than a simple projectile.

In other words, the cost to engineer and build a satellite capable of withstanding the launch may exceed any savings.

Somehow I'm more skeptical about their claim that electronics can withstand 30,000G than that they can make this launcher work. Very interesting approach anyway.

The proximity fuses used in WW2 naval AA guns could handle 20000g and were using vacuum tubes. Electronics are more durable than you give them credit for.

one thing I've never understood about these kinetic launch vehicles is that, if something falls from orbit, it tends to burn up. But if we want to launch it from ground to arrive at orbital altitude with orbital velocity, then we have to launch it faster than orbital velocity and from thicker atmosphere.

So, do we cover it in big, aerodynamic heat shields or something?

> one thing I've never understood about these kinetic launch vehicles is that, if something falls from orbit, it tends to burn up. But if we want to launch it from ground to arrive at orbital altitude with orbital velocity, then we have to launch it faster than orbital velocity and from thicker atmosphere.

The kinetic launch vehicles achieve orbital altitude but not orbital velocity. They require a rocket engine to accelerate them to orbital velocity. This is no different from Blue Origin flights where they get to space, but then fall back down to earth (relatively slowly).

To achieve "orbital" altitude you need to start with enough kinetic energy to make it to the Karman line (100km) with zero (or more) energy left. The kinetic energy a tthe start of the trip needs to equal the potential (gravitational) energy at 100km (neglecting friction).

Gravitational energy is U=mgh so, for 1kg and 100km (g = 9.8m/s^2)...

U = 1e3 x 9.8 x 100e3 = 9.8e8

Kinetic energy = 1/2mv^2 so...

9.8e8 = 1/2 x 1e3 x v^2

Solving for v...

v = 1,400 m/s = 5.04e3 km/h (3355mph) or roughly mach 5 (if I got all my units right)

Launching a projectile at mach 5 will result in a significant amount of heat, but nothing close to the heat from orbital velocity (6.8 to 7.9 km/s => 24,840–28,080 km/h)

https://en.wikipedia.org/wiki/Gravitational_energy

https://en.wikipedia.org/wiki/Kinetic_energy

https://en.wikipedia.org/wiki/Orbital_speed

Yes. All the feasible proposals for ground based kinetic launch have involved significantly high percentages of thermal shield materials. We basically do cover it it big aerodynamic heat shields.

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