I've read that in practice, the weight of a bicycle in use doesn't vary - the lighter the frame & hardware, the heavier the lock required! :)

The price of carbon fiber has been a major factor, along with the difficulty of using it in manufacturing. Both of those have improved by orders of magnitude, and if one company I'm familiar with succeeds, they'll cut the cost of the fiber by another factor of 10 while greatly improving the quality. These incremental advances are truly changing the equations for many of the things you're pointing out.

As someone peripherally involved in "New Space", I'll say that the advances in technology really are making some of those fanciful ideas possible, even economically feasible. People right now are putting their money into those new ventures, and they're not doing it for entertainment but because the numbers pan out at least as well as many of the dotcom ventures. SpaceX has cut the cost of launch by 50% just by using well-tried industrial cost management methods - faced with exorbitant pricing for turbine pumps, the company built their own at 1/10 the cost. If the reusable first stage pans out, that will cut the cost by about another 1/2 (they think it will be better than that, but I think their long term costs will be higher as they transition their systems to support the more rigorous requirements of manned launches - that will affect all of their systems, even the unmanned launch ones.)

Another example, 3D printing has already proven itself with multiple different entities successfully printing components and even entire rocket engines, with costs and production times reduced by 90%.

Bottom line - much of the extremely high cost of space has been the government-run cost-plus market structure and extremely careful engineering practices. In fairness, I think this was necessary for the early days, but now we can move past that and into a more market-driven economic model with fixed prices on off-the-shelf products. Consider that development costs on a rocket engine are going to be on the order of a billion dollars, regardless of whether 10 or 10,000 of that engine are produced; but if 10,000 are built the amortized cost is $100,000 vs. $100,000,000 per engine.

If reusability pans out, the fuel cost of a launch is less than $500,000.

I learned a while back that the cost of an F-18 was more than 1/2 software. The plane had 1600 VME boards. (VME was a common instrumentation/computer bus, back in the 1970s and 1980s). All that fancy over-the-horizon radar, integrated electronics, head up displays, etc. takes a lot of computing power and software. I'm sure that is even more true for the newer planes.

On the Titanic, steerage pasengers paid IIRC $8, while the top tickets were $30,000. I think that's the equivalent of $1,000,000 or so today.

I read somewhere that flying NYC to LA on a corporate jet costs about $30,000 - not sure if that is total or per passenger. So that's something close to the cost target. If they can get you there in 1/2 the time, is it worth $60,000? These are the numbers they're probably working with. Note that Virgin Galactic has flights booked solid for seven years worth of flights at $200,000 each, and those flights are just up and down for entertainment.

The major US air carriers have definitely gotten out of their repeating-bankruptcy spiral and are registering record profits these days. Through mergers and other tactics, they have eliminated almost all of the low cost alternatives, and at nearly all major airports the majority of the gates and flights are 'owned' by one or two airlines, eliminating effective competition. Note that they raised prices when fuel prices went up, and kept them their afterwards, and added baggage fees, etc. - soon they will be charging extra for the right to breathe actual air, I'm sure.

I saw the SR-71 at the Abbottsford Air Show in British Columbia a long time ago. The plane took less than an hour from takeoff in San Francisco to arrival in BC. They did a 'slow' fly by, which was deafening. Then they did a faster fly by and went vertical into the low hanging clouds.

It's quite possible that Virgin Galactic, or some other entity working on suborbital flight systems, could make this whole idea moot. Rather than worry about sonic booms, get completely out of the atmosphere. Think of it as a two-stage passenger-carrying intermediate range ballistic missile, probably with horizontal take off and certainly horizontal landing. This system could provide 3000 mile / 5000 km flights at Mach 5, 10 or more, depending on where the economic sweet spot is, with near-zero concerns for sonic booms. I have heard that Virgin is considering this as a future service. Of course, if the Skylon project pans out, it's doable with one stage.

I forget - cube => square

I get almost 28 MPG on long trips at 67 MPH, about 25 MPG at 75 MPH. That cubic drag coefficient really starts to hurt.

IIRC the reason golf balls have those little dimples is that they cause little 'air ball bearings', which both increase the distance and reduce turbulence, which reduces the wobble and increases accuracy.

Or just throw a wall of bullets in front of it. I've read that during the VietNam war, to avoid ground-to-air missiles the US fighters often flew low to the ground - they were so fast that by the time you saw one coming over the ridge it was too late to shoot at it from the ground. But the North Viets figured out that they could have spotters on radio or telephone or whatever, and when one was spotted in the next valley over, everyone in this valley would just start shooting into the air. Some of those bullets got in the way of the fighter, and they did bring some down that way. Or so I've heard.

In theory, it's quite possible. Supersonic planes are going at bullet speed, so a stationary object has the necessary relative velocity to act like a bullet.

IMHO the fundamental issue is the inexorably increasing cost of speed - doesn't drag increase as the cube of velocity, all other things being equal? You can make things more and more pointy, but that has decreasing returns.

Maybe (my idea recently) you could push very high pressure air out the tip of the plane to insulate against the heat build up (but pressurizing that air would also cause heating ...) Maybe with such an analogue of supercavitation you could reduce the drag by 'hiding' the vehicle behind the supersonic wedge created at the front?

That's mostly wrong. The US SST was well along when the issue of sonic booms was raised, not as an anti-EU competitive measure but because there was existing law already on the books that banned supersonic flight over the continental US, at _any_ elevation IIRC, except over certain (very large) military reservations. One of the reasons the SST was cancelled was because lobbying by Boeing et al failed to overturn that sanction, making it impossible to run SSTs from NYC to LA, which was the primary target market. Without overland flights there was no way for any supersonic airliner (or any airliner for that matter) to make money. The Concorde development was continued in the face of that for purely national pride and EU cooperation reasons - basically by then its completion and operation were a political necessity even though nobody thought it could make money. Politicians in UK and France would _both_ have to had the guts to put thousands of workers out of work, at a time when the unions basically ran both countries.

It's possibly worth noting that according to some thing I read a year or two ago, biologists who knew such things believed that the reason bears died out in Africa lo these many years ago is that they are omnivores, and designed to do reasonably well at many things but are not optimized for any of them. But Africa gradually became populated by specialists who did _one thing_ very well, and the bears were gradually out-competed at everything.

Sturgeon's Law

That made me think - you could actually incorporate xCoin, so folks whose postings are popular would actually get paid a tiny amount, and everyone pays a tiny amount to post. I'm not sure of how this would exactly work, but it's certainly possible. Maybe it costs $1/month to join, you get 1000 up/down votes per month. So if someone's posting got 3000 votes (either up or down), their account would accrue $3 less whatever the website's overhead is ($.50 for purposes of argument), netting $2.50. It's not a zillion dollars, but could be fun. Maybe only get paid 1/2 for a down vote, but IMHO downvotes should get something, as it still represents traffic and interest. Maybe have a threshold - no pay for less than 10 votes.

Kinda like the 'ante' in poker? Such a site might be successful without advertising. This is a good enough idea that I'm proposing it to some friends.