Dr. Phil Metzger Profile picture
Director, Center for Microgravity Research & Education @UCF. Previous: co-founder of NASA KSC Swamp Works. Space Mining. Space Settlement.

Oct 6, 2023, 9 tweets

I got word today that our research into the Starship launch pad anomaly is being forwarded uphill to NASA HQ. They are focusing on what we learned about launch/landing pad failure modes and how we can make lunar landings safer. /1

2/ What we found is that the pressure that built up beneath the launch pad was comparable to a volcanic eruption when the buildup of hot gas that evolves from the magma busts apart the caprock and expels it. (Pic: Fagents & Wilson, Geophys J Int 113(2): 359.)

3/ The theory on these volcanic eruptions predicts a range of velocities that matches what was measured for the ejected chunks of concrete from the Starship launch pad — about 90 m/s.

4/ But to explain the mass of gas needed to expel at this velocity, we had to conclude that groundwater under the pad was vaporizing. We estimated the water based on crater volume and permeability of the sand under the pad. It is in the range that agrees with theory.

5/ This raises the question about ice in lunar polar soil under a launch pad. If the pad cracks and hot gas is pushed through (like we think happened for Starship) then vaporization of the ice may create a similar situation. Ice can be as much as 5%wt (actually higher), which…

6/…predicts that ejection velocity of a lunar launch pad could be even faster than what happened for Starship. 5 wt % vs 1 wt % on this plot.

7/ So we need to develop methods to prevent this. It shouldn’t be hard to do. Examples: make the pad thicker. Measure the ice before construction. Put vents under the pad. In fact…

8/…we are already collaborating with Cislune on a project to develop these technologies. “Deflector cone and vented launch pad” — read more here: spaceref.com/science-and-ex…

9/9 So that’s how the Starship launch pad anomaly, while not *desired* ofc, turned out to produce insights for engineering lunar landing technology. This is the message that got attention and is being sent up to NASA HQ.

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