Making Laser Launch Take Off

Laser launch technology could replace conventional chemical rockets with a more efficient, higher specific impulse (ISP) form of rocketry. The basic idea is to shine a powerful laser - or a bunch of less powerful lasers - onto a rocket to deliver energy to heat reaction mass to a high enough temperature to make it expand rapidly and drive the rocket in reaction as it is expelled. Jordin Kare has suggested a form of rocket that is quite simple - a heat exchanger and a big tank of liquid hydrogen.

The problem is that this technology requires a substantial amount of investment in fundamental technologies - improved lasers, the heat exchanger, development of tracking systems, etc. And even once it's working, it requires a very substantial investment in infrastructure before you could make a rocket that could fly into orbit - fields of lasers being the biggest investment.

It seems to me that laser launch could be dramatically accelerated, by finding short term goals worth investing in, that require somewhat less advanced technology, and less capital investment. And it also seems to me that getting any investment for the concept will be difficult, so long as it aims to compete head to head with existing chemical rockets. It would have to jump directly from "no capability" to "better than existing rockets". That's a high first hurdle! Not to mention that your competitors will be telling potential customers and investors that they're crazy - not because it's a bad idea, but because they'll lose out if you succeed!

But what if one didn't have to go all the way to orbit? And what if you could actually convert those nay-saying competitors, into customers?

What if you initially targeted a very limited niche market - call it "rocket enhancement" or "payload expansion". The idea would be to simply provide a strap-on booster for existing chemical rockets. This booster would be used during the first boost phase, when the rocket is nearer and moving slower - reducing the technical challenge of tracking it with sufficient accuracy and beaming power through a wavery atmosphere, and allowing a working system to be put into operation with less up-front development time and money.

It would only have to improve the net ISP of a conventional rocket marginally in order to provide some value - allowing one to start with a relatively small booster. That means that the "field of lasers" can be substantially smaller - reducing capital investment.

Customers for such a system would be makers of rockets that can achieve orbit, but who want to deliver larger payloads, or deliver payload to more challenging orbits, with their existing rocket design - expanding the target market for a smaller rocket.

This approach also raises potential for variations on the laser launch concept. E.g. there might be a modest gain from simply directing laser energy into the exhaust expansion bell of a conventional rocket? Most of the energy would be lost in gases already out of the bell, but any small increase of a first stage's thrust would translate directly into greater upward acceleration, without adding *any* reaction mass to the rocket.

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