Were you told the rationale for continuing without a fix?
- Yes, the solution to cryo-pumping was to "pot" the honeycomb between the composite facesheets of the LH2 tanks with injectable closed-cell foam. This solution was relayed to the chief engineer. He rejected it because it would have added about 500 kg of weight to the two LH2 tanks "south" of the CG and the vehicle was already in trouble with its CG location. It was already too far "south" because of the overall triangular design of the vehicle and substantial weight growth in the ramps of the aerospike engines. Further weight "south" of the CG was not permitted. By contrast, weight growth "north" of the CG was encouraged, since there was already ballast in the nose of the vehicle that could therefore be removed. But the LOX tank was aluminum and didn't have the cryo-pumping problem.
- Wow. Just... wow. AvWeek didn't report on the CG issues that I recall, but that follows what heard, that the linear aerospike was very much overweight from the design values, and the low CL generated by the shape was causing larger wings aft - and wings are just dead weight.
- Do recall if the aft end of the CG range was tanks-full or tanks-empty? I could see it driving weight into the design either way. And BALLAST is not something you're wanting to have in an SSTO. 🫢
Didn't they later experiment with a layer of foil inside the tank, and improved an aluminium tank that could be as light as the carbon one. But as the aluminium tank was out of the scope of development they could use it.
