Earlier this month the Ares I-X team conducted a successful frustum separation test. The success of the test showed that the separation charge is fully capable of splitting the joint of the frustum’s aft ring — an important hurdle to clear.
The test simulated the first separation event that will happen about 2 minutes after launch when the propellant in the first stage booster is used up. After the booster burns through all the propellant, the first stage (bottom half of the rocket) splits from the upper stage simulator and crew module/launch abort system simulator (upper part of the rocket). This split happens at a piece of the rocket called the frustum.
The frustum is an upside-down cone-shaped piece that connects the skinnier first stage to the thicker upper stage. The large forward (top) section of the frustum, which connects with the upper stage, is eighteen feet in diameter while the aft (bottom) end is twelve feet in diameter to attach to the booster. During separation, linear shaped charges detonate at the frustum’s aft ring, allowing the first stage to return to Earth where it will be retrieved and refurbished for other Ares missions.
The shock created by the charge was measured by accelerometers and acoustic pressure sensors. Measuring the shock is an important part of the test because if the bang is “too big for the buck,” it could damage some of the avionics or other pieces of hardware. It’s a balancing act between having a bang that is strong enough to separate the metal but not so strong as to damage the working parts of the rocket.
The test took place at ATK’s Promontory facility in Utah. The data from the test will be used to prepare for the Ares I-X flight and will help Ares I engineers make sure the calculations they are currently using are correct.