Comment by ctkrohn | Hacker News Reader

Comment by ctkrohn | Hacker News Reader

Air transport is one area where technology has seemingly stagnated, or even reversed. Airliners seem pretty much the same as when I was a kid. You certainly don't get to your destination any faster. There have been improvements -- aircraft such as the 787 are built with light and strong composites; the A380 is the biggest airliner ever; low cost carriers have driven down prices; you can get WiFi on certain flights. But you're not going any faster, or traveling any more comfortably.

Compare that to the period from 1955 - 1975. Jets entered commercial service, displacing slow and noisy gas-powered propeller planes. The Concorde made its first flight in 1969, entering service shortly after. The US had its own supersonic airliners on the drawing board. There were even proposals for hypersonic transports. We ended up getting stuck with cosmetically identical jetliners and a series of unmanned hypersonic test vehicles. Remarkable feats like SpaceShipOne are few and far between.

Aerospace technology relies on inspiration. "Because we can" used to be a large motivator. It's tough to get around economic or military reality, but at the same time it's sad to see fewer mind-blowing engineering achievements. Most of us couldn't afford a Concorde ticket, but I bet there were plenty of people who still thought it was damn cool.

The problem with this analysis of aerospace progress is that you are focusing on the most obvious factors for differentiation and missing the real revolutions that are continuing to happen within the field. Yes, airplanes today have the same approximate shape and engine types that they had thirty years ago, but that is because the Cambrian explosion of the late forties and early fifties converged upon shapes and configurations that were simply the best option given all of the different factors that had to be balanced.

The concord was fast, but speed is not everything. The reason that there were no other supersonic passenger craft is because once this particular prestige project actually started flying everyone saw what a bad idea it really was; if the plane had been built and flown by private companies it would have been retired a decade earlier. It was cramped, had abysmal fuel efficiency, and required a great deal of maintenance to keep flying. It also turned out that few people actually needed (or were willing to pay for) the speed advantage being offered.

The current advances in passenger aircraft happen in areas that are not obvious to a casual observer; more efficient engines that require less maintenance, avionics that can fly the plane themselves and fly by wire systems that reduce weight and can increase safety. A modern sedan car looks very similar to one from twenty or thirty years ago, but the modern vehicle is superior in just about every possible way, The thing that you tend to forget about all of those "mind-blowing engineering achievements" is that most of them failed to have any significant impact -- optimization to an extreme along a single performance axis is neat, but not really as useful or interesting as most people think.

Flight fundamentally depends on cheap, portable energy. When energy is cheap and travel times are long, spending more energy to get there faster makes sense. But the Concorde was already on the marginal side of that curve.

Those faster planes, not to mention things like flying cars and jetpacks, are dreams from the era of (apparently) limitless cheap energy.

Passenger space ultimately depends on cheap energy too, which is why the innovation we see is in things like entertainment systems, climate control, bigger windows, reduced noise, and so on that don't require more space.

I just had a thought... could a nuclear powered aircraft be possible? With some form of electric turbines? Even if the thing could only land at a couple airports, it could easily serve as a bulk transport for people / equipment to get part-way to their destination. I mean, it'd have to be huge...

I mean, sure, people would freak about a flying reactor, if only on principle. But that sort of thing dies down with time.

/me starts hunting for weights of marine nuclear reactors

The idea is nice, but I think it's impossible. Just think of the amount of material you'd need to take in the plane for the shielding. And what about the water used to power the turbines? You'd also need a huge water tank. It's just way too heavy for the moment. We first need to find a more efficient (in the case of a plane, lighter) way to get energy out of a nuclear power source.

Actually, after a bit of hunting... an An-225[1] can carry 250,000 kilos, and a 100 megawatt SSTAR reactor[2] is projected to weigh ~500,000, with 10 megawatt ones projected to be ~200,000. A quick perusal of Wikipedia suggests other ones may be smaller yet, including a couple which have been made (but I can't find any weights except for the SSTAR).

Surely we can make a bigger plane, especially if the power output of these things is enough to significantly increase the power of the engines, meaning the plane won't have to be as light (I'm thinking a flying-wing plane). Though does anyone know what the approx. power of those engines might be?

[1] : http://en.wikipedia.org/wiki/Antonov_An-225 [2] : http://en.wikipedia.org/wiki/SSTAR

It has been done before.

In the 1950s, both the US and USSR did some fairly extensive research into nuclear-powered aircraft, culminating in flight tests by a US NB-36H carrying an operational 3 MW air-cooled nuclear reactor and a Soviet Tu-119 with a reactor powering two of its engines. The US had progressed quite far in developing nuclear-powered engines, culminating in Heat Transfer Reactor Experiment-3 (HTRE-3), but the project was cancelled in 1961 before it could go much further, with the Soviet project being cancelled soon afterwards. [1]

The program didn't solve all the problems that nuclear-powered aircraft could case, such as escaped radiation after crashes, but it did prove that crew shielding could be done safely at a low-enough weight that the concept remained feasible.

Scientific American featured an article [2] a couple of years ago about some people's recent calls to resurrect the idea for commercial use. But the inherent safety risks remain a big issue.

It's probably an inevitable development at some point, once the core problems have been solved. And with a new generation of high-temperature reactors emerging, such as South Africa's Pebble Bed Modular Reactor, we may see reactors that are ideally suited to this sort of thing coming through.

[1]http://en.wikipedia.org/wiki/Nuclear_aircraft

[2]http://www.scientificamerican.com/article.cfm?id=nuclear-pow...

exactly the sort of reply I was hoping to get. This site is fantastic.

And oops ^^; should've checked for "nuclear aircraft" on wikipedia first. I dove into details without hunting for attempts first. Thanks for the summary!

Space travel technology too. Both fields have had massive advances in terms of the underlying technology (and safety, which you overlooked) but have "stagnated" in terms of the practicality of shuttling people from one place to another.

However, with space travel, there's a growing consensus that sending people is too impractical and, importantly, needless. We can send robots to do our job for us. Likewise, I think air travel with stagnate because air travel will become almost inconsequential for business purposes and will merely be a leisure activity where time is not of the essence.

I'm sure studies are being done in to it, but I wouldn't be surprised if advances in communications technology and work culture are starting to have strong negative effects on compulsory business travel.

We can send robots to do our job for us.

That's kinda the general feeling I get when looking at anything space-oriented. Which is part of the reason I get a bit excited reading up on recent robotics & AI progress.

People need too many supporting structures to be at the forefront of space travel, methinks. Once a tech has been proven, people adopt it pretty quickly; if anything, space travel has been disproven in terms of practicality, until some major change occurs.

I think the biggest improvements were in safety, efficiency and emission/noise reduction. Have you heard the A380? It's incredibly silent. Not as bad-ass as the Concorde, though.

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