In late 1960, RAE decided that the proposed HTP/kerosene third stage for Black Prince would not be able to put a communications satellite weighing 600lbs into a 5 000 nautical mile orbit. [NB this is not geosynchronous orbit.], and so Saunders Roe were asked to produce a study for a liquid hydrogen upper stage. This theye then did, with their usual thoroughness. The basic design data were:
| All up weight | 7 000 lb approx. |
| Propellants | 5 000lb approx. |
| Specific Impulse | 400 lb.sec/sec |
| Two boost phases: | |
| Boost | 3 500lb for 8 minutes |
| Cruise | 44lb for 2 hours |
| from Saunders Roe publication SP510 |
They concluded that such a design could actually put 900lbs into a 5 000NM orbit or 600lb into a 9 000NM orbit.
However, the nature of the second stage is very undefined, since by this time it was clear that Black Prince probably was to be replaced by some form of Anglo French laucher.
The boost phase was to use the main motors [see layout above] for the boost phase, with turbo pumps. The cruise phase used the 2 small motors at a very low chamber pressure [perhaps 2 atmospheres], thus dispensing with the pump. In the vacuum of space, the low combustion chamber preesure is no drawback. Although a good idea, it does mean carrying the dead weight of the large chambers and pump up to altitude.
This cruise phase would mean then that the stage would spiral up to its final orbit after another 2 hours!
2nd February 2000
... back to the liquid hydrogen page ...