Russian space chief, former NASA astronaut Scott Kelly trade barbs on Twitter

The space partnership between Russia and the U.S. looks shakier and shakier every day.

That partnership has been fraying badly since Russia invaded Ukraine on Feb. 24, spurring the United States and a number of other countries to impose new economic sanctions. Russian space officials have decried these sanctions; in response, they have stopped the sale of Russian-made rocket engines to American companies and halted launches of Russian-built Soyuz rockets from Europe’s Spaceport in French Guiana, among other measures.