Scientists at NASA are attempting to come up with a novel way of saving many tons off the total lift-off weight of its future spacecraft.
The heavier the spacecraft, the greater the propellant requirement. In NASA circles, cutting down on the propellant needed to carry a spacecraft out of the Earth’s atmosphere could mean saving millions of dollars per mission.
All re-entry spacecraft that are launched from Earth need to carry a heavy heat shield along with it, otherwise the craft would burn-up when re-entering the Earth’s atmosphere. The heat shield protects the ship from the searing 3000°F heat of re-entry, so it isn’t something that can be left behind.
DIY Heat Shield Using Moon Dirt
The researchers at the NASA Kennedy Space Center in Florida are in the initial phases of testing a “Regolith Derived Heat Shield for a Planetary Body Entry and Descent System with In-Situ Fabrication”. (1)
The regolith (soil) in question could be taken from the moon, Mars or even asteroids and manufactured onsite, possibly by some kind of robotic device.
Michael Hogue of the Kennedy Space Center is the man who came up with the idea, and the NASA Innovative Advanced Concepts (NIAC) Program has funded the concept research. The initial testing period is focused on trying out different techniques and has so far been very successful.
Using materials similar to that which will be available on the moon, the engineers constructed small, dome-shaped bricks 4 inches in diameter and 2 inches thick. One side of the bricks were heated with a blowtorch up to a temperature of 4000°F, quite a bit higher than that encountered on re-entry.
The bricks stood up to the test without degrading, but more importantly the other side of the brick – the spacecraft facing side – remained at a passable 200°F throughout.
Emulating Realistic Re-Entry
The focused heat of a blowtorch is one thing, but now the researchers will try and emulate the conditions faced upon atmospheric re-entry, when they put the bricks to the test at the arc jet facility at NASA’s Ames Research Center in California.
There they will be subjected to searing plasma streams that will more closely mimic re-entry conditions. According to Hogue, this is the test that will decide whether the idea is feasible or not (2).
If successful, the massive weight savings gained at take-off would be beneficial in a large number of ways, not least of which being the smaller rockets able to carry more equipment with less propellant. Getting the heat shield off the moon or an asteroid would not generate any problems either, because the low gravity means less force is needed than on Earth for take-off.
NASA has been looking at other heat shield methods, and recently successfully tested their Hypersonic Inflatable Aerodynamic Decelerator (HIAD) technology, with the third installment of the Inflatable Reentry Vehicle Experiment (IRVE-3) (3).
The Inflatable Heat Shield
The inflatable heat shield technology resembles a giant cone of inner tubes, similar to a child’s stacking ring toy, and brings with it the same benefits as the “moon bricks”, reduced weight and increased size.
The most recent test launched the IRVE-3 over 288 miles up into space, before re-entering the atmosphere at Mach 10, ten times the speed of sound.
The heat shield performed beautifully, and is further evidence of the giant steps forward that the innovative engineers and researchers of NASA are taking.
Space Technology Program deputy director James Reuther sums it up nicely:
“Today’s test is the first example of what we are going to be doing in the Space Technology Program during the coming months and years. We are building, testing and flying the technologies required for NASA’s missions of tomorrow.”