What are hypersonic missiles and why do they matter?

America, China and Russia are engaged in a new arms race, spending billions to develop new missile technology, but how different are these hypersonic missiles from what has gone before? And as countries work out how they might use them, are they increasing the risk of triggering conflict? Contributors: Dr Gustav Gressel, Berlin office, European Council on Foreign Relations Dr Laura Grego, Massachusetts Institute of Technology Dr Marina Favaro, Institute for Peace Research and Security Policy, University of Hamburg Dr Cameron Tracy, Centre for International Security and Cooperation, Stanford University Presenter: Tanya Beckett Producers: Bob Howard and Sheila Cook Researcher: Chris Blake Image: Military parade in Beijing marks 70th anniversary of Chinese People's Republic (Credit: Zoya Rusinova/TASS via Getty Images)