Ok I really got to thinking about this, and I think a few here don't fully understand rocket design.
First there are two kinds of rockets, solid fueled and liquid fueled. Solid fuel rockets are like most tactical missiles (Say a Sidewinder). The first solid propellant was Black Powder. They are great at long term storage which is why they are used in weapons which need to sit around but be ready on demand. Also they offer more power in relation to the space they take up meaning more more rockets in the magazine. On the flip side they are not as powerful as liquid fueled rockets. Some space launches use solid fuel rockets like the two side mounted boosters on the Space Shuttle (Called SRB for Segmented Solid Rocket Boosters.) Now Liquid Fueled rockets are a different creature. These are like the V2 rocket. Liquid fueled rockets have two chemicals that are mixed causing an explosion of thrust. For example Liquid Oxygen and some kind of Hydrocarbon fuel or Liquid Hydrogen. One of these chemicals is the fuel while the other is the reaction mass, the fuel basically allows the remass to explode and produce thrust. Liquid fuels offer a lot of power but are dangerous to store (The explosion on the K-219 was due to liquid fuel mixing with water from a leaky hatch). Refueling isn't really a problem if a liquid fuel rocket is used, you bring the equipment that can make fuel and remass on site. But we can do better if a rocket is say nuclear powered the Fuel is Uranium and the Remass is liquid hydrogen (remember all that steam coming from the Saturn V? Thats excess liquid hydrogen turning to gas). So hydrogen is one of the most common elements in the universe, in theory a we could just distill it from local water for a return voyage. Ok yes the down side is the exhaust is “somewhat” radioactive but if we use a conventional rocket for take off and the nuclear rocket for exo-atmospheric flight and take off from the LZ who cares, all that radiation is in a country we felt the need to invade.
But why even have part of the rocket land at all to deploy troops? Make the troop carrying section of the rocket a lifting body (like the Space Shuttle) that the troops parachute from during sub-orbital flight (don't worry its dark, you won't even be able to tell your falling 60,000 feet! Ooorah!), then the lifting body glides to a landing in friendly territory or is even recovered by a aircraft carrier somewhere on the other side of the world. This would be a lot like the Antipoldal Bomber the Germans designed during WWII.
Now do we really need a big rocket NASAs new Aries launch vehicle. Why not put it on the top of big aircraft with a loiter capability? When needed the launch vehicle detaches from a very high altitude and turns on its rocket and goes sub-orbital to the target.
Ok so lets design a rocket to insert troops that can be launched from the continental US. Let have an Aries booster with a lifting body on the top stage. The lifting body carries say a dozen SOF troops with an automated navigation system. The Aries sends its payload on a suborbital trajectory skipping off the atmosphere over the target area out SOF troops make a HALO jump as the lifting body fires a detachable rocket boosting it in to a higher trajectory towards friendly territory where it lands on autopilot.
Now as we can see its feasible to build such a launch vehicle. But whats the down side? Well stealth is almost impossible during the boost phase due to the massive exhaust plume thats sets off warning sirens in the control center of Russia's Strategic Rocket Forces HQ! So anyone with a basic space monitoring capability to know a operation is under way. When the lifting body skips off the atmosphere its plainly visible to everyone below, we all saw the footage of the ill fade Columbia burning up in the atmosphere. Now direction of flight is a problem, unless we forward deploy rockets overseas rockets (since current submarine launch tubes are too small to be of value modified boomers are out) would be launched from Cape Canaveral (or whatever they are calling it these days) or Vandenberg AFB. Launches from The Cape are to the east (to use the spin of the Earth to add velocity) this is good for targeting our good buddies in the middle east but lousy for say China or North Korea. Vandenberg is good for launches over the pole which is good for targeting Northern China and North Korea but targets in the southern hemisphere become a problem. Targets in Australia are out, so Crocodile Dundee has nothing to fear from Space Marines.
I would put this in the realm of possibility but a stealthy cargo aircraft capable of hypersonic fight (like the fabled Aurora spy plane) would be better.
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