Lift the launch site to the top of the atmosphere with hydrogen. Tether with helium filled \"potato chip bag\" tubing. Lift hydrogen propellant via tether. Concentrate 02 in situ.
Artisteroi
how about a green engine instead of a fuel? Chemical rockets, Bah!
Richie Suraci
There is plenty of sea water not being used as fuel....
Rustin Lee Haase
This is just another example of NASA\'s current \"Lack of Real Vision\" situation. We used to launch space shuttles back when the US was a space faring nation and their main fuel (ignoring the boosters) was Hydrogen with Oxygen as the oxidizer producing nice clean water as a product. You can\'t get much greener than water. (yes, I now water is generally regarded as blue)
Slowburn
Granted hydrazine is nasty stuff but it is a widely industrial chemical and is a less toxic but more energy intensive to produce fuel really greener?
For station keeping and deep space operations an ion engine will provide much greater efficiency.
............................................................................................................................ Liquid hydrogen is overrated as a fuel, rocket or otherwise. It energy density is a joke plus it migrates through everything and is energy intensive to produce, and concentrate. (liquify or compress) Dealing with LH requires expensive alloys to deal with the ridiculous cold.
Ultra refined kerosene is a much better liftoff fuel although the high quality diesel fuel produced by the Fischer-Tropsch method might work just as well and be cheaper. I am not a real fan of LOX as the oxidizer, being a cryogenic liquid it doesn't store well and any were in the system that can not be really well insulated will get freezing condensation but for non-weapon use it does appear to be the best.
NYIDave
Laser powered space elevator with power generated by remote reactor. this can eliminate breakout velocities and enable and allow greater cost/payload ratios. While we wait for this, how about a magnetic rail gun style slingshot. The technology seems there already and ready to modify and adapt.
Slowburn
re; NYIDave A space elevator requires a orbital tower. An orbital tower must be built from the top down, this requires moving a lot of stuff around in space which requires rockets and rocket fuel. This space to space fuel is what NASA is looking for a replacement for. The orbital tower will also provide a much better energy delivery route than a laser.
Rail guns are not really suited for orbital insertion, they require a super surge of electricity subject the load to ridiculous acceleration and an EMP event. There are much more efficient linear accelerators that also would provide a survivable launch. A laser powered rocket might work but for space you will still require reaction mass.