January 10, 2015

Sub-orbital airliners? Not if you know much about economics and physics

Filed under: Economics, Technology — Tags: , , , , , — Nicholas @ 02:00

Charles Stross in full “beat up the optimists” mode over a common SF notion about sub-orbital travel for the masses:

Let’s start with a simple normative assumption; that sub-orbital spaceplanes are going to obey the laws of physics. One consequence of this is that the amount of energy it takes to get from A to B via hypersonic airliner is going to exceed the energy input it takes to cover the same distance using a subsonic jet, by quite a margin. 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. But let’s suppose we can get the price down far enough that a seat in a Mach 5 to Mach 10 hypersonic or sub-orbital passenger aircraft is cost-competitive with a high-end first class seat on a subsonic jet. Surely the super-rich will all switch to hypersonic services in a shot, just as they used Concorde to commute between New York and London back before Airbus killed it off by cancelling support after the 30-year operational milestone?

Well, no.

Firstly, this is the post-9/11 age. Obviously security is a consideration for all civil aviation, right? Well, no: business jets are largely exempt, thanks to lobbying by their operators, backed up by their billionaire owners. But those of us who travel by civil airliners open to the general ticket-buying public are all suspects. If something goes wrong with a scheduled service, fighters are scrambled to intercept it, lest some fruitcake tries to fly it into a skyscraper.

So not only are we not going to get our promised flying cars, we’re not going to get fast, cheap, intercontinental travel options. But what about those hyper-rich folks who spend money like water?

First class air travel by civil aviation is a dying niche today. If you are wealthy enough to afford the £15,000-30,000 ticket cost of a first-class-plus intercontinental seat (or, rather, bedroom with en-suite toilet and shower if we’re talking about the very top end), you can also afford to pay for a seat on a business jet instead. A number of companies operate profitably on the basis that they lease seats on bizjets by the hour: you may end up sharing a jet with someone else who’s paying to fly the same route, but the operating principle is that when you call for it a jet will turn up and take you where you want to go, whenever you want. There’s no security theatre, no fuss, and it takes off when you want it to, not when the daily schedule says it has to. It will probably have internet connectivity via satellite—by the time hypersonic competition turns up, this is not a losing bet—and for extra money, the sky is the limit on comfort.

I don’t get to fly first class, but I’ve watched this happen over the past two decades. Business class is holding its own, and premium economy is growing on intercontinental flights (a cut-down version of Business with more leg-room than regular economy), but the number of first class seats you’ll find on an Air France or British Airways 747 is dwindling. The VIPs are leaving the carriers, driven away by the security annoyances and drawn by the convenience of much smaller jets that come when they call.

For rich people, time is the only thing money can’t buy. A HST flying between fixed hubs along pre-timed flight paths under conditions of high security is not convenient. A bizjet that flies at their beck and call is actually speedier across most intercontinental routes, unless the hypersonic route is serviced by multiple daily flights—which isn’t going to happen unless the operating costs are comparable to a subsonic craft.

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