Dr. Phil Metzger Profile picture
Oct 6 9 tweets 3 min read Twitter logo Read on Twitter
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.) Image
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. Image
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. Image
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. Image
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… Image
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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More from @DrPhiltill

Aug 23
Thanks to all who sent info on the Starship launch wind conditions. I haven’t responded to all the replies individually yet to express thanks since I was swamped with three proposals last week and now I’m on travel. HOWEVER,… 1/2
2/ …I have a new request for help.

Does anybody remember seeing the brown dust cloud that drifted north toward Port Isabel from the launch site? We need to estimate it’s altitude. Cloud height is hard to judge, but…
3/ …if you can estimate the angle it was above the horizon and how many minutes from then until it was overhead, we can use that to estimate its height (using the winds data).

This is important because…
Read 11 tweets
Aug 16
#WeirdWednesday thoughts. Can civilization be studied like it is a **material** that forms naturally in the cosmos? What are the material properties of this bizarre material?

I'm wondering because papers that try to answer the Great Silence (or Fermi Paradox) treat it this way, and it is very helpful. 🧵 /1
2/ We can consider civilization to be a phase change of matter. Phase changes include melting, freezing, vaporization, and condensation. Matter is in one state, then something happens and it goes to another state.
3/ The phase changes that move matter from disorder toward order include freezing and condensation, whereas melting and boiling move matter from order toward disorder. Consider the order achieved by the phase transition that makes a snowflake.
Read 18 tweets
Aug 8
The UAP debates reminded me of a personal story about handling evidence and judging likelihood. I think this is interesting & amusing.


On Shuttle mission STS-128 the rocket exhaust blew out 3,500 tiles from the side of the flame trench. /1 Image
2/ The bricks were smashing into each other as they blew, fragmenting into millions of pieces of all sizes. The results were devastating to the perimeter of the pad. This is what the security fence looked like about a kilometer away. See the brick fragments? 🤯 Image
3/ My research group collected an unbiased sample of fragments so NASA Marshall could use a realistic range of fragment sizes in their computer modeling of the event. This is @Ryan_N_Watkins and John Lane measuring and weighing fragments. (I’m holding the camera.) Image
Read 26 tweets
Aug 1
Lots of people are telling me that the radar observations make the aviator TicTac observations more likely an advanced vehicle, but tbh the radar observations are my biggest cause for doubt. (I used to be a radar/avionics engineer for NASA for many years chasing such anomalies.)
2/ Here are a few of the many weird things we saw on radars/avionics at NASA.

(1) for a while, we started getting weird signals on the Space Shuttle TACAN systems and we were in a NOGO for launch because of it. We went into emergency mode trying to figure out their source...
3/ We worked around the clock for a month, so our office was split into three shifts and we handed off shift-after-shift while trying to chase down the anomalies. We looked into every possibility. Ionospheric skip, onboard signals, cruise ships leaving Port Canaveral. All no joy.
Read 41 tweets
Jul 17
Some clarification about the possible interstellar material from the ocean bottom — why scientists care.

Also, did you know that not just the elements of our world are stardust (interstellar), but even an important class of *molecules* here may be interstellar? /1
2/ The elements heavier than helium were made in the fusion and/or supernova of stars. It was swept into the disk that formed our Sun and planets. So people are pointing out that we already have interstellar material here. That’s true, but there is something else more interesting
3/ We find that asteroids and comets have organic molecules in them. We don’t think these small bodies like asteroids had enough gravity, warmth, and water to form and concentrate SO MUCH organic material, so how did it get there?
Read 19 tweets
Jun 12
This is a well written piece by @SineadOS1 criticizing the hype that Starship radically lowering launch prices will send the space sector into hyper-growth. Mandatory reading to be informed, IMO, but I want to give a nuanced response… 1/n

2/ Many of us space technologists have argued for years, long before Starship was even imagined, that space will grow to much more than the trillion dollar industry Sinead discusses. But we have argued this growth will not be overnight. It will take decades. /… Image
3/ The problem is that it is hard to find near-term or even mid-term business cases that justify the extra transportation cost, harsh environment, and logistical challenges of making or doing things in space.
Read 23 tweets

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