To probe the edges of flight, NASA, together with Australia's Department of Defence and America's Air Force Research Laboratory, wants to see if they can make aircraft work flying many times the speed of sound. Together, they're working on a project called HIFiRE, for Hypersonic International Flight Research Experimentation Program.

This week, a successful test brought the HIFiRE rocket to a height of 172 miles, with a maximum speed 7.5 times the speed of sound.

From the Australian Department of Defense:

The success of this test launch takes us one step closer to the realisation of hypersonic flight,” Dr Zelinsky said. Hypersonic flight, involving speeds of more than five times the speed of sound, has the potential to provide immense social and economic benefits.
“It is a game-changing technology identified in the 2016 Defence White Paper and could revolutionise global air travel, providing cost-effective access to space,” Dr Zelinsky said.

Several earlier tests of hypersonic machines have failed, like this Army missile that exploded prematurely.

But the potential for a hypersonic plane is huge: with that much speed, it would be impossible for an enemy to move anything on the ground after radar detected the plane, letting it either capture pictures immediately or drop bombs almost unimpeded.

Here's what NASA said about the HIFiRES program in 2012:

NASA, AFRL and Australia's Defence Science and Technology Organisation (DSTO) are working with a number of partners on the HIFiRE (Hypersonic International Flight Research Experimentation Program) program to advance hypersonic flight -- normally defined as beginning at Mach 5 -- five times the speed of sound. The research program is aimed at exploring the fundamental technologies needed to achieve practical hypersonic flight. Being able to fly at hypersonic speeds could revolutionize high speed, long distance flight and provide more cost-effective access to space.

Check out another angle on the rocket below.