a launch system with externally supplied energy is a massive infrastructure project. If we muster a capability for large infrastructure project a huge railgun launch would be much simpler.<p>With regard to incremental improvement upon what we already have - *&#x2F;LOX chemical launch, we have only scratched the cheapest and simplest way to boost specific impulse for the first stage - like 3 times - and thus to decrease the total launch mass 2+ times : <a href="http:&#x2F;&#x2F;www.astronautix.com&#x2F;lvs&#x2F;gnom.htm" rel="nofollow">http:&#x2F;&#x2F;www.astronautix.com&#x2F;lvs&#x2F;gnom.htm</a>  (much simpler than Skylon)<p>&quot;The concept was evidently been proved on a subscale tactical missile, the PR-90, now on display at MAI&#x27;s museum at Orevo, north of Moscow. The PR-90, with a launch mass of only 1500 kg, of which 550 kg was payload, could reach an altitude of 40 km and a range of 100 km. The booster unit used 200 kg of RAM-10 ballistite with a specific impulse of 180 seconds to get the missile up to ram-air ignition speed. Then the air-augmented unit, with a specific impulse of 550 seconds, cut in and used 300 kg of propellant to boost the vehicle to its 1 km&#x2F;s cut-off speed. An equivalent liquid propellant missile (such as the American Lance) weighed over twice as much. A solid propellant equivalent (such as the French Pluton) would weigh three times more&quot;