Whilst researching propulsion systems for a project I was amused to learn that Project Orion (Nuclear Pulse Propulsion) was an idea to propel a spaceship, using atomic bombs going off underneath the ship. As each bomb went off the ship was forced higher, as it would be. Makes you really glad that they didn't actually try it! The theme was used by Stephen Baxter in his novel "Ark". I would bet high odds that if certain of our allies actually decided to explore this idea the chances are that it wouldn't be held on their own turf.