After the demise of the joint NASA/ESA gravitational wave mission LISA, it’s good to learn that the US has not completely given up on the idea of a space-based experiment to detect gravitational waves. A paper submitted to arXiv on 22 November 2011 proposes a mission called LAGRANGE. (You’ll be pleased to know that this is yet another acronym. This one stands for LAser GRavitational-wave ANtenna at GEo-lunar Lagrange points.) It uses the same sorts of ideas as in LISA, but it would be vastly scaled down: LAGRANGE would have spacecraft at three Lagrange points in the Earth-Moon system, with an arm length of 670 000 km. LAGRANGE would thus not be as sensitive as LISA to long-wavelength gravitational waves, but the mission would be much cheaper.
ESA, of course, have their own plans for a scaled-down version of LISA: they hope eventually to launch the New Gravitational Wave Observatory.