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Comment by vkou | Hacker News Reader

At the expense of 'Everybody dies if the slightest thing goes wrong.' And 'Everybody better be wearing space suits... Unless you want to get Souz-11'ed.

There is more then an order of magnitude of complexity between designing a vehicle that can travel at Mach 2, and one that can travel at Mach 22. Personally, I'd pass on the risks of hypersonic re-entry for my SEA->NYC flight... And on having to pee into an astronaut diaper.

Space travel (And a ballistic suborbital hop is 90% of the way there) is, as a mode of transportation, incredibly dangerous.

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Why space suits? Just pressurize the cabin so everybody can breathe. As for Gs, just make sure they're pointed toward the back of the seats and you won't need G suits.

See https://en.wikipedia.org/wiki/Soyuz_11

Didn't know about that one. Thanks for the link. Still, passenger jets are pressurized today and they rarely lose pressure. The technology is much more reliable now.

IIRC pressure loss incidents are common, but not newsworthy because nothing really bad happens. The air pressure is still high enough to allow people to breathe, so you just need to supply oxygen-enriched air while the plane descends to 10000 feet.

With suborbital flights, neither breathing nor descending more quickly would be an option.

You don't need to go all the way to space to die of hypoxia, cruising altitude for modern jets is plenty good for that: https://en.wikipedia.org/wiki/Helios_Airways_Flight_522 (and several other examples of non-airliner "ghost planes" that I'm too lazy to look up)

I think you are confusing suborbital and orbital travel.

A suborbital flight that brings you all the way across the Atlantic will have almost the same speed and energy requirements as an orbital flight.

Just take a look at the typical orbit of a SpaceX second stage over the Atlantic: https://youtu.be/zBYC4f79iXc?t=32m13s - A suborbital flight that just barely goes back deep enough into the atmosphere over Africa to slow down would look almost exactly the same and wouldn't even be 100 m/s slower.

Compare that to the tiny ballistic arc of the first stage. That's how your suborbital flight would look like if you want to hit the atmosphere at a speed that doesn't require a heat shield.

There's a lot of possible trajectories, and one doesn't have use a ballistic one. Once out of the atmosphere you could leave low thrust on for the entire journey, alleviating concerns over both weighlessness and the need for excessively high speeds.

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