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Why We're Not Going To See Sub-orbital Airliners
glowend writes: Sci-fi author Charlie Stross has an article about sub-orbital flight, and why we'll never see it as a common mode of transportation. Quoting: "Yes, we can save some fuel by travelling above the atmosphere and cutting air resistance, but it's not a free lunch: you expend energy getting up to altitude and speed, and the fuel burn for going faster rises nonlinearly with speed. Concorde, flying trans-Atlantic at Mach 2.0, burned about the same amount of fuel as a Boeing 747 of similar vintage flying trans-Atlantic at Mach 0.85 ... while carrying less than a quarter as many passengers. Rockets aren't a magic technology. Neither are hybrid hypersonic air-breathing gadgets like Reaction Engines' Sabre engine. It's going to be a wee bit expensive."
Stross also makes a more general proposition that's particularly interesting to me: "One of the failure modes of extrapolative SF is to assume that just because something is technologically feasible, it will happen. ... Someone has to want it enough to pay for it—and it will be competing with other, possibly more attractive options."
Stross also makes a more general proposition that's particularly interesting to me: "One of the failure modes of extrapolative SF is to assume that just because something is technologically feasible, it will happen. ... Someone has to want it enough to pay for it—and it will be competing with other, possibly more attractive options."
So, you're not going to see it, because it doesn't save money. Except, it has the potential to be many times faster. Which is a reason to use it that isn't "it costs less." So the argument can't hope to support its thesis. If it happens or not is not based on just if "because we can." It is going to happen or not based on the actual advantages of being faster, their value, and the final cost.
We can certainly say, based on our experience with Concord, that if it is fast enough and safe enough the rich will use it, and if it as safety issues, they will abandon it quickly.
I think the thing being missed here is that people are in a hurry. If I can fly a 747 from Seattle to Japan and the flight takes 14 hours, I would pay more to be able to do it in 7. That's an easy choice. Time spent in the air is generally wasted time. Turn trans-Pacific/Atlantic into a weekend trip instead of the current 3 days of travel time and there's a market for it.
The futuristic prediction that it would be economical to take a sub-orbital flight from NY to LA is probably not going to happen, but for trans oceanic and/or China/Japan to Europe. Definitely a market there.
"Freedom in the USA is not the ability to do what you want. It is the ability to stop others from doing what THEY want"
Yup, this raise one of my big complaints about some SciFi stories: lack of economic plausibility.
Science Fiction is great for looking at how we might deal with various potential technologies. Readers are perfectly happy to suspend disbelief and accept whatever technology is proposed. What readers aren't willing to do is suspend disbelief and accept people behaving implausibly.
To write good science fiction, you need to accurately portray people. You can make up the technology, but you have to get humanity right. And that means you have to get the economics right.
This is exactly the problem I had with reading the Hunger Games. Everything worked, except why would a society with hover cars and other advanced technology have need of the services of the districts? Surely they didn't need coal, and yet they had a whole district dedicated to mining it. The lack of economic sense pulled me out of the book. Instead of thinking about the characters, I was thinking about why the society that was described didn't make any sense.
Sure it would be the fastest transPacific transport, but who can afford it.
Some of the flight is going to be in microgravity, There goes your lunch
And of course if something goes wrong, your chances of survival are zero as well.
Similar to space tourism I guess
An adjunct proposition to consider is that certain technologies will never disappear, no matter how many attractive alternatives arise.
I'll offer one example right now: paper.
Discuss.
If it weren't for deadlines, nothing would be late.
While Heinlein's juvenile fiction was, well, juvenile, I like that it at least played with the concepts of economics.
I will bite, if I gave you a tunnel between New Zealand and Australia how would you do that?
It's pointed to in the summary and was not missed - there were not enough people in a hurry to sustain Concorde flights.
An ironic thing is the 747 was opposed within Boeing in the late 1960s because it was thought that only supersonic airliners would have a place on long hauls in the 1970s - so very few were built in the first batch. As mentioned in the summary the 747 went on to render Concorde mostly irrelevant.
I've done some research into hypersonic technology, and it's not strictly true that hypersonic flights are necessarily less efficient per passenger mile. Sure, up to this point it has been the case, but we haven't explored in detail.
The US currently has tested a hypersonic glider that goes a heck of a long way, with a surprisingly good glide ratio, above Mach 20. Apparently it was to glide for thousands of miles, while only descending maybe 20 miles, implying a tremendously high glide ratio, over 100:1. If that's true, then you could have extremely efficient flight at Mach 20.
These "waverider" planes use radically different aerodynamics, so the old rules don't apply. They're nothing like the Concorde.
I love Mondays. On a Monday, anything is possible.
The article (well worth reading this time) argues that such a target market has left the building and is already on "bizjets" to avoid the time consuming fuss of getting onto an airliner and having to stick to a schedule. It also points out that suborbital spaceports are not going to be in the middle of cities so the time to get to and from them also has to be considered. Those factors seem to reduce the small market you suggest to zero. Expensive, fixed timetables and little or no time saved compared with "bizjets" in the same or lower price range that leave when you want and land closer to where you want to be.
Sucks, but all that extra effort to go supersonic/hypersonic prices it out of most civilian situations.
It's likely to be like this. First you have to get to New Mexico to get on the sub-orbital flight, and it only flies on Tuesdays. Not a lot of use if you are in a hurry.
I recommend reading the full article on the website, it isn't very long and I should have read it before I wrote my single point post above. The article covers many more points including those you raised above.
I'm hoping for a bungie sling with a cannon on the end, swung from the side of the space elevator. And for landing, a net attached to a pole that rotates around the space elevator. Then you can use regenerative braking and recover some electricity during the landing.
It's pointed to in the summary and was not missed - there were not enough people in a hurry to sustain Concorde flights
Wikipedia sites other, different reasons. Specifically, the decline of the airline industry after 9/11, combined with uncertainty because of the crash, and the withdrawal of maintenance support by the manufacturer. Sir Richard Branson was trying to pay lots of good money to buy them and continue operating, but it was that last one, lack of maintenance support, that foiled him; not any speculation about how much of a hurry people were in.
Branson would be operating them today, but for the withdrawal of maintenance support and that is just a historical fact. So there was business interest, with real cash money offers, to keep it going, and there was never any failure to sell tickets that would imply lack of interest; regardless of if interest was based on being in a hurry, or just the appeal of a premium service.
"Nonlinear" is not an equivalent phrase to prohibitively expensive. He doesn't actually say a thing about fuel consumption costs. It's all about "expending energy" which is not actually a significant cost constraint in rocketry.
For example, as I recall, getting a 100 kg adult to Earth orbit using kerosene and liquid oxygen costs around $10,000 in propellant. It goes up to $30,000 if you use liquid hydrogen and liquid oxygen. The actual cost of the energy required to put a person in orbit, if it were electricity? Around $1000 per person. The cost for suborbital to the other side of the world, will be at most about half those figures with a significantly lower energy cost (perhaps about a quarter that required to go to orbit). And it's obviously going to cost substantially more than just fuel cost.
Now look at what he writes, aside from the preliminary hand waving about non-linearity, air resistance, expending energy, rockets not being magical, etc, none of which says anything about actual constraints on real world rockets, he spends more than two thirds of the article discussing the two nearly irrelevant aspects I noted before.
....We may see a return of supersonic flight within the next 15 years.
Thanks to better understanding of how sonic booms are generated from the shape of the plane and definitely way better jet engine technology, we may be able to very soon build a business jet seating 10 passengers capable of flying at Mach 1.6 at ranges up to 6,000 nautical miles with just about no sonic boom audible on the ground even when the plane is fly at Mach 1.6.
How is this possible? First, aerodynamic research using computational fluid dynamics have identified ways to minimize the pressure wave buildup that causes the sonic boom in the first place with very careful shaping of the fuselage and wings. This makes to possible to effectively eliminate the audible sonic at speeds up to Mach 1.6. Secondly, modern engine design using variable cycle engines (GE Aero Engines successfully tested the technology on a engine intended for the Advanced Technology Fighter program that resulted in the F-22A Raptor) means high-bypass turbofan fuel efficiency at subsonic speeds but can change configuration to fly at supersonic speeds with a small amount of reheat (afterburning) to keep fuel consumption and harmful exhaust missions as low as possible. Finally, by keeping the top speed to Mach 1.6, it means less structural heating from flying at supersonic speeds and less need to run a lot of reheat (afterburning) on the engines, which means lower fuel consumption and less need for expensive high-temperature rated stainless steel or titanium structural parts like those used on the Concorde.
I've read companies that sell fractional ownership of private jets such as FlexJet or NetJets would immediately buy 50 of these supersonic business jets once approved for production. The ability to fly from New York City to London in around 4 hours as opposed to the circa 7.5 hours with current jet airliners makes it very attractive to business customers, especially since many live by the motto of "time is money."
Err..
First, the Concorde cruised at Mach 2.0 without reheat. On the Concorde, reheat only added some 20% (IIRC) to the thrust was used mainly to accelerate to cruise speed.
Secondly, to design a more powerful/fuel efficient engine without reheat, you need to handle higher flows, temperatures and pressure.
Reheat is a "cheap and easy" way to work around this issue, although at the expense of fuel efficiency.
That said, using more advanced materials which can handle higher temperature and pressures to build more powerful and efficient engines is the normal business in jet engines.
Using modern materials and designs, one could surely design a high/medium bypass turbofan that is quite more efficient than Concorde's turbojets.
There's another problem. Turboprops are in fact more efficient for long range and are capable of only marginally slower speeds than modern turbofan aircraft but they are comparatively very noisy. As a result, they are far less comfortable to travel in and often incur additional penalties due to noise on take off.
If you read the actual article (and perhaps some of his replies in the comments) you'll find he isn't really saying "never", he's talking about the short to medium term: the next few decades. And the main thrust of his argument depends on post-9/11 security measures rather than overall pricing. That won't last forever either ... or at least I hope not ... but it probably won't change much in that timeframe.