How Quickly Will the Latest Arms Race Accelerate?

First time accepted submitter tranquilidad writes "Russia was concerned enough about the U.S. development of a Prompt Global Strike (PGS) capability in 2010 that they included restrictions in the New Start treaty (previously discussed on Slashdot). It now appears that China has entered the game with their 'Ultra-High Speed Missile Vehicle.' While some in the Russian press may question whether fears of the PGS are 'rational' it appears that the race is on to develop the fastest weapons delivery system. The hypersonic arms race is focused on 'precise targeting, very rapid delivery of weapons, and greater survivability against missile and space defenses' with delivery systems traveling between Mach 5 and Mach 10 after being launched from 'near space.'"

Re:Pointless

[daem0n1x]

Forget it.

Boys like to compete with each other by comparing dick sizes. This is just the grown up version of it. Big boys playing with their big dicks of mass destruction.

Re:Pointless

[Immerman]

Actually, not really. Going fast is easy - it's going stably hypersonic that's hard, and that's only a relevant concept while inside an atmosphere, not in space. About the only weapon-oriented research that would be applicable to space travel are fuels with higher specific impulse, and point-defense systems that can vaporize incoming debris as easily as RPGs. And force-fields I suppose, but it seems like we're going to need to develop some completely new scientific principles before those become a viable research option.

The trip to Mars is slow not because the rockets aren't strong enough, but because the fuel is too heavy to carry the quantity you'd need to get to Mars quickly. And in general as the specific impulse (newton-seconds per kg) of a propulsion system increases, the absolute thrust (Newtons) tends to decrease, making the sort of propulsion systems you'd want for interplanetary transport utterly unsuitable for rapid-deployment missiles. Witness ion drives, the best propulsion system we have for interplanetary rocketry - for a given mass of drive and fuel they can accelerate to *much* higher speeds than chemical rockets, but it takes much longer to get there. That's a winning combination when you're talking about having to cover the millions or billions of miles between planets, but the Eart is only a few thousand miles around - interplanetary drives will barely even be getting warmed up in that time scale. Even a hundredfold increase in absolute thrust - enough to make the entire solar system readily accessible to manned exploration on a timescale of months, would still be insufficient to even get a rocket off the ground - .1G acceleration for weeks on end will get you to insane speeds, but only if you don't have ten times that force keeping you in place.

Moreover, the single biggest cost of surface-to-orbit rocketry, the one area where missile technology is more likely to be applicable, is in the cost of the rocket itself (>90% by some estimates), making reusable rockets the watchword of the day, a concept utterly inapplicable to a system designed to explode as violently as possible at it's destination. As for the potential of cheaper disposable tech, getting to orbital altitude and back down again takes only a few percentage of the amount of energy it takes to actually reach orbital velocity once at altitude - if powered by magical massless pixie dust the missile would still have to be over ten times larger to reach orbit, add the diminishing returns of real-world fuel and you're likely talking at least 20-50x larger. And that's just to deliver the same tiny warhead - thanks to those diminishing returns on fuel delivering a useful payload of 10x the mass is going to take considerably more than 10x the rocket. It's not impossible that we might make some missile-based advances in rocketry that will scale to orbital rockets 500x as large, but it's unlikely they'll hold a candle to the advances that 1/100th of the funding would have returned on actual surface-to-orbit rocketry research.