I don’t know. A few trillion is probably the total cost of NASA down the decades, and I don’t see how if instead of lots of little missions they had spent it on one big one we’d be on our way to the stars. To Mars maybe.Darkflame wrote:I'm still pretty convinced if you chucked a few trillion at the problem we could have probes going at 25% of C without too much issue. Presumably with externally supplied momentum, either via solar sails and a lazer, or some sort of array of satellites around the sun each giving it a little magnetic push as it goes past.
The problem is the laws of physics. To e.g. send something like New Horizons but twice as fast, to cut the journey time to the nearest star to 4,000 years (!!), you need to supply four times the energy, as energy = ½mv² scales with the square of speed. But that does not mean 4x the fuel. It means much more as every kg of fuel or power systems you add also needs accelerating. It means bigger rockets with more stages to get off the Earth. And so on.
Do the math and you find that the mass required doesn’t grow quadratically, it grows exponentially.
https://en.wikipedia.org/wiki/Tsiolkovs ... t_equation
It’s mass, not energy, as only reaction mass ejected from the craft will accelerate it. So space lasers aren’t the answer, while solar sails provide far too small a push and only work close to the Sun.
To have any hope of getting to the stars we need to be able to do so from space: bypass the most expensive part of the Tsiolkovsky rocket equation and build and fuel big-ass rockets entirely in space. To do this we need not just a fragile and expensive low-orbit space station but large scale permanent bases in deeper space, probably on or among the asteroids which can supply resources and serve as platforms without the twin burdens of Earth’s gravity and atmosphere we have to contend with launching from here. But we are many decades from that.
