NASA鈥檚 boldest gamble to slash the costs of launching reusable spacecraft is
looking riskier than ever. The future of its X-33 vehicle is in question after
an innovative composite fuel tank failed on 3 November.
The $1.3 billion X-33 is one of several NASA projects aimed at
replacing its ageing space shuttle fleet. Most involve modest improvements in
technology. But the X-33, which aims to cut the cost of space launches by a
factor of ten, is on 鈥渢he razor edge of feasibility鈥�, according to John Pike, a
space analyst with the Federation of American 快猫短视频s in Washington DC. The
craft is produced by Lockheed Martin鈥檚 鈥淪kunk Works鈥� in Palmdale, California,
which specialises in high-risk projects.
The X-33 is designed to demonstrate two crucial technologies: a novel
鈥渁erospike鈥� engine
(快猫短视频, 6 July 1996, p 36), and lightweight
graphite-epoxy composite liquid-hydrogen fuel tanks
(see Diagram). The craft is
a half-scale prototype of VentureStar, a single-stage vehicle which NASA
originally hoped would fly by 2004.
Advertisement
Even before the latest setback, the fuel tanks were causing problems. 鈥淎s
originally designed, the composite tanks would save about 20 per cent weight,鈥�
says a Lockheed Martin spokesman. But modifications to strengthen the two
8.8-metre-long tanks had already made them about as heavy as metal designs.
Now it seems even these changes may not be enough. The latest blow came after
engineers at NASA鈥檚 Marshall Space Flight Center in Huntsville, Alabama, pumped
110 000 litres of liquid hydrogen into one tank to test whether it could support
the liquid oxygen tank that would sit on top of it at launch. After the hydrogen
was pumped out, engineers noticed that the outer graphite-epoxy skin and an
insulating honeycomb structure had separated from the inner skin along a
structural seam.
Lockheed Martin is putting a brave face on the failure. 鈥淚t鈥檚 what we鈥檙e in
this programme to learn,鈥� says a spokesman. However, the company last month
announced that it plans to 鈥渁ggressively pursue the reduction of capital
expenditures鈥�. VentureStar, which will require a large investment by Lockheed
Martin, could be among the casualties.