Point-to-Point Suborbital Flight

[ptpsuborbital]

To those interested in learning about point-to-point suborbital flight (e.g., New York - Tokyo in under 3 hours), please visit my blog at ptpsuborbital.com. I've been posting articles and videos about the revolutionary changes coming to the commercial aerospace industry. Virgin Galactic upcoming 'space tourist' flights are just the beginning.

Thanks for reading!

[Nibb31]

Suborbital is useless for point to point transport. It takes much less energy, and is therefore cheaper and easier, to just go supersonic or hypersonic in the atmosphere, and we all know how that turned out for Concorde.

Virgin Galactic flights are designed for zero-g joyrides that land at the launch site, not for transportation. It takes hours just for the Eve mothership to reach the SS2 drop altitude, which negates any transit time gains from the Suborbital part of the mission, and the SS2 is designed to go high, not fast.

[Chris P. Bacon]

and we all know how that turned out for Concorde.

Yup, it was considered the safest aircraft in the world until some junk fell off an aging DC-10 which took off ahead of it. No one wanted to fly on her after that.

It's a shame we never replaced her with more modern and efficient designs.

Edited August 3, 2014 by Chris P. Bacon

[shynung]

Yup, it was considered the safest aircraft in the world until some junk fell off an aging DC-10 which took off ahead of it. No one wanted to fly on her after that.

It's a shame we never replaced her with more modern and efficient designs.

It's not only that, but also the high per-passenger cost that brought her down. It takes a lot of energy to get anything going beyond the sound barrier, no matter what we power them with.

The Air France Concorde crash from the DC-10 junk was the last drop in a cup already full.

[Nibb31]

With only 12 units built, it was a commercial failure decades before the Air France crash. The only reason AF and BA kept flying them was national pride.

Anyway, looking at the way the OP's post was written, it looked more like a spam than a proper engagement in a discussion thread.

[K^2]

Suborbital is useless for point to point transport. It takes much less energy, and is therefore cheaper and easier, to just go supersonic or hypersonic in the atmosphere, and we all know how that turned out for Concorde.

It's not about energy. If you could shoot a suborbital out of a cannon, it'd be really cheap. I've done a rough estimate, and LAX to JFK (Los Angeles to New York, about 4,000km) requires mass ratio of 1.35 under glide ratio of 7 and I_SP of 3,000s at mach 2. These are the rough numbers for a Concorde. In practice, it's a bit more due to takeoff and landing. But this is a good baseline.

In contrast, the same suborbital trajectory requires ground velocity of 5.4km/s (e = 0.72). Add 1.5km/s for atmosphere, and you need 6.9km/s for the launch. Even with LH2/LOX rocket, that still gives you mass ratio of 4.8. So that's really expensive. But only because we're using a rocket to accelerate the suborbital craft. Using, say, a launch loop, the same suborbital flight can be done for peanuts. 5.4km/s is just 4kWh / kg. In contrast, the 0.35kg of kerosene above would yield 3.9kWh / kg. So with a launch loop or similar tech, suborbital flights suddenly become quite competitive. Of course, that only makes sense if you are going to be building a launch loop for orbital launches anyways.

[ptpsuborbital]

Thanks to all for replying to my post and offering your opinions. My intention was not to spam -- but merely to provide a source of information about point-to-point suborbital transportation. Whether it ever transpires or not, it's an interesting concept and one that many are taking seriously -- including the FAA.

[Nibb31]

So with a launch loop or similar tech, suborbital flights suddenly become quite competitive. Of course, that only makes sense if you are going to be building a launch loop for orbital launches anyways.

Sure, but notwithstanding that a launch loop is still impossible to build and highly impractical itself, there would only be one 8000km-long launch loop on Earth's equator, making it pointless for point to point travel.

[K^2]

Sure, but notwithstanding that a launch loop is still impossible to build and highly impractical itself, there would only be one 8000km-long launch loop on Earth's equator, making it pointless for point to point travel.

I have no idea where you got that 8,000km figure, but it's silly. At just 3G, you need less than 1,000km. Launch loop doesn't have to be equatorial, either. It's with chemical rockets every few m/s count. With launch loop, extra 400m/s isn't a huge deal.

But hey, that's just one example. The big picture is that we either figure out how to make launch to orbit cheap and routine, or we are screwed as a civilization. There aren't any alternatives. Right now, launch loop looks like the most plausible of known options. And we'd need several at different latitudes and in different countries to make access to LEO convenient. We might figure out a different way to do this. But whether we find a way to push off the ground, or find a very cheap way to do reaction drives for space launches, we will need to be able to launch to orbit from multiple locations around the world at a reasonable price. And that means reasonably priced suborbital flight as a consequence.

Maybe we won't get there. Then we'll suffocate on this planet and become extinct sooner or later. And that's a good enough reason to try in my books. And if economical interest in suborbital flight is going to be the thing that helps us get over that barrier, so much the better.

[Tommygun]

Well Point-to-Point Suborbital Flight at least makes more sense than skipping across the upper atmosphere with some of those hypersonic craft proposed for the general public.

Going from micro gravity to one plus G every 5 to 15 minutes as it skips is too much for the untrained public. You'll need mandatory airsickness bags Velcroed to everyone's face.

Ultimately we need to find cheaper and less polluting ways of mass space flight. I can't imagine how much pollution would be generated to lift even a million people into space let alone the number of passengers you see on international flight.

Unless some truly unconventional technology comes along, commercial flights for the general public I think will be just short joy rides.

[Godot]

Well Point-to-Point Suborbital Flight at least makes more sense than skipping across the upper atmosphere with some of those hypersonic craft proposed for the general public.

Going from micro gravity to one plus G every 5 to 15 minutes as it skips is too much for the untrained public. You'll need mandatory airsickness bags Velcroed to everyone's face.

Ultimately we need to find cheaper and less polluting ways of mass space flight. I can't imagine how much pollution would be generated to lift even a million people into space let alone the number of passengers you see on international flight.

Unless some truly unconventional technology comes along, commercial flights for the general public I think will be just short joy rides.

Or until we are able to design the suborbital shuttles much larger than conventional planes, so that a single suborbital fligh transports the passenger load of sevral conventional planes, so that the polllution per passenger delines rapidy

[Firov]

Or until we are able to design the suborbital shuttles much larger than conventional planes, so that a single suborbital fligh transports the passenger load of sevral conventional planes, so that the polllution per passenger delines rapidy

Kerolox is rather polluting, since it generates carbon dioxide, but something using Liquid Oxygen and Liquid Hydrogen are, in theory, completely clean. Generating only water vapor. In practice they run a bit rich and so the exhaust contains some H2, but that's largely harmless.

Unfortunately, the low density and cryogenic properties can make H2 a bit of a pain to use for a first stage. Though a number of launch systems used it as a first stage propellant despite that. The Shuttle, obviously, but also the Delta IV and Ariane 5.

[Kryten]

Unfortunately, the low density and cryogenic properties can make H2 a bit of a pain to use for a first stage. Though a number of launch systems used it as a first stage propellant despite that. The Shuttle, obviously, but also the Delta IV and Ariane 5.

Delta IV usually uses solids to augment it's first stage, and Shuttle and Ariane V have/had mandatory large solid boosters.

[Firov]

Delta IV usually uses solids to augment it's first stage, and Shuttle and Ariane V have/had mandatory large solid boosters.

Quite right, for the Shuttle and Ariane 5, though there's hardly any need to even mention it since both launch platforms are so well known. The Delta IV, however, is a different matter. You're thinking of the current Delta IV Medium+, which relies upon a variable number of strap-on GEM solid rocket boosters (between 2 and 4).

However, remember. There are different variants of the Delta IV, and some of them have not relied upon those solid boosters. The original Delta IV Medium didn't, and the Delta IV Heavy also doesn't use GEM boosters. The GEM boosters were just added to give slightly more payload capacity. The Delta IV is quite capable of flying without them.

Edited August 4, 2014 by Firov