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I think they were suggesting that you could save fuel for once you're out of atmosphere, so that you're not fighting air resistance when you start a burn to get into orbit.

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You could save a decent chunk of your fuel this way. Maybe 25% or so.

In exchange for that, you have to build your rocket and satellite to withstand 10,000 gees of acceleration and hypersonic flight through the lower atmosphere. And somehow build a rail gun that can fire something the size of an office building.

You use an extremely long track, not high acceleration.

Hard to do if you’re aiming straight up.

You'd have to re-purpose something like a deep mining shaft from a diamond mine, then stick a giant rail gun in it, almost like Germany's V-3 cannon[1] but on steroids.

[1]https://en.wikipedia.org/wiki/V-3_cannon

No we aren't aiming straight up because we need to get into orbit. We need to go sideways as fast as possible. As long as you're not aiming at the ground you will always aim "up" but not straight up.

“Imagine putting one or many of those new Space X internet satellites into a rail gun that goes straight up.”

Firing sideways could save you much more fuel but also means you’re in the lower atmosphere at much higher speed and for much longer.

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