Suborbital Airliners?

[Aghanim]

That's silly. Contrary to a widely popularized speech, we don't do things because they are hard, we do things because they are worth doing. Especially when it requires a substantial effort. In fact, the bigger the effort, the more justification you need.

We don't build suborbital airliners because there is no demand for $200 000 express plane tickets. Concorde was a complex machine, but it flopped due to lack of demand. Nobody is going to start building rocket fuel factories and storage facilities at Heathrow, JFK, and Dubai International Airport for a handful of passengers every year.

Rocket fuel? Do you mean kerolox engines? That doesn't seems economic to me at all...

[Nibb31]

Rocket fuel? Do you mean kerolox engines? That doesn't seems economic to me at all...

Of course it isn't. Actually, the OP mentioned the Reaction Engines A2 (a suborbital airliner version of Skylon), which uses LH2. There are no LH2 facilities at international airports, so it would require a special area at the airport for production, storage, and handling of LH2. It would also require specially trained personel for all the activities related to this specific aircraft. The infrastructure cost would be huge.

[Aghanim]

LH₂. (I'm using subscript so it looks more cool) How about the aircraft volumetric efficiency of the fuel tank? LH2 is not dense... Although it only flies for ~2 hours still, it means that every time it landed it need refuelling

[SargeRho]

The A2 isn't suborbital, but a Hypersonic airliner, from what I understood anyway.

Question: How well developed are pulsed detonation engines, and how viable are they for suborbital "hops"?

[Red Iron Crown]

LH₂. (I'm using subscript so it looks more cool) How about the aircraft volumetric efficiency of the fuel tank? LH2 is not dense... Although it only flies for ~2 hours still, it means that every time it landed it need refuelling

That's no different from regular airliners which refuel after every landing, too. It's just not efficient to carry around more fuel than safety margins require.

[Lukaszenko]

It's just not efficient to carry around more fuel than safety margins require.

Nor safe. The worst aviation disaster in history was (in more ways than one) a result of ignoring this advise.

[shynung]

The A2 isn't suborbital, but a Hypersonic airliner, from what I understood anyway.

Question: How well developed are pulsed detonation engines, and how viable are they for suborbital "hops"?

Yes, the A2 in question was not suborbital. In order to use its high top speed, it has to fly over oceans or uninhabited territories, as supersonic flight over land is currently prohibited. For long trips such as London to Sydney, it had to go through The North Pole, over the Pacific Ocean, then arrive at Sydney from the north. Suborbital airliners were supposed to get over this problem by flying at an altitude where the air is too thin to transmit sonic booms to the ground, eliminating the need for unorthodox routes.

As far as I know, current PDEs are mostly either small-scale hobby projects, or experimental engines. We have yet to build one capable of actually propelling an airliner-sized aircraft (though, at least there's one highly modified light aircraft, a Rutan Long-EZ, flying on such an engine). Also, PDEs still need atmospheric oxygen to run, so it would run into the same problem as a scramjet would: choked out of air at high altitudes. With enough TWR, they could provide the initial acceleration for the "hop", but it would probably be rather uncomfortable.

Also, PDEs are quite noisy. From what I saw at Youtube, the things sounded like machine guns.

Edited March 4, 2014 by shynung

[PakledHostage]

Nor safe. The worst aviation disaster in history was (in more ways than one) a result of ignoring this advise.

If you are referring to the Tenerife accident, then to say that it was at all caused by carrying excess fuel is a bit of a stretch. So many things went wrong that day. All of them contributed to the accident in some way. KLM flight 4805 wouldn't have needed to haul itself into the air at low speed (where a lower takeoff weight due to less fuel on board might have helped) if everything else hadn't gone wrong first.