SR-72 and NASP can benefit the airborne refueling to flight to the orbiter.

SR-72 and NASP can benefit the airborne refueling to flight to the orbiter. 

The thing is that the new type of airplanes like SR-72, or NASP (National Aerospace Plane), would have the ability to make the ballistic jump to the suborbital trajectory that can jump through the ionosphere during their missions. The normal profile of this kind of ultra-fast aircraft would be accelerating their speed to level over Mach 10, and then the aircraft can dive to the suborbital jump, what would take it to the Van Allen Belt can make the craft to the ability to benefit the ion layer as the stealth missions. 

The airborne refueling can also make SR-72 type hybrid rocket aircraft ability to fly to the LEO (Low Earth Orbit) or if there is some satellite, what can refuel that thing there is no limit for flying that kind of small shuttle straight from the ground. There is a possibility that that next-generation shuttle-aircraft would fly even higher than the suborbital trajectory in a simple way. Another SR-72 can take fuel from the other in the maximum altitude, and that makes that there is always enough fuel for that another craft would fly higher than they could to fly straight from the ground. 

The simplest possible way is to use two aircraft, where the first will pull another one behind it. When that aircraft combination is high enough the puller would just turn to dive, and the rope would sling the rocket aircraft to the orbiter. Or it can give more power to that craft, what might be the normal rocket engine aircraft. 

The system that makes this kind of flight possible requires the new type of engines. And one possibility is to use the so-called turbo-rocket ramjet or scramjet concept. The normal turbine or turbo-jet engines would raise the speed to the level, where the ramjet can be started. Then the speed would have risen to the level that makes it possible to start the scramjet engine. 

And when the craft would rise above the atmosphere the air intake would be closed, and the fuel and oxygen would start to inject the chamber, which turn to rocket. The reason why the use of the air, what is taken from the atmosphere should continue as long as possible is that the load of the oxygen is smaller in that kind of case, where a large number of it can be taken from the atmosphere. 

SR-72 https://en.wikipedia.org/wiki/Lockheed_Martin_SR-72

NASP: https://en.wikipedia.org/wiki/Rockwell_X-30

Image: https://en.wikipedia.org/wiki/Lockheed_Martin_SR-72#/media/File:Lockheed_Martin_SR-72_concept.png