Dr. Phil Metzger @DrPhiltill Twitter profile

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Dr. Phil Metzger

6 months

Three collections of threads from over the years, sorted by how interesting (IMO). I hope you enjoy! 1. IMO, the best 🧵s. 2. The 2nd best set. 3. The 3rd best.

Dr. Phil Metzger

@DrPhiltill

6 months

This third and final 🧵 of 🧵s is for the those that I put into the 3rd tier of interestingness. I hope some will enjoy them, but they are probably not for all. /1

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Last Seen Profiles

@ManonMarsault

@Shlimaz

@Poarohercule1

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@ShouraHashemi

@ComicBookDads

@mame_salon

Dr. Phil Metzger

@DrPhiltill

3 years

The most difficult part of space exploration isn't rocket science, it is economics.

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Dr. Phil Metzger

@DrPhiltill

3 years

Here's a concept I developed at NASA 18 years ago: "Multipole Radiation Shielding." Our director called it the First Generation Star Trek Shield. My lab lead had the idea to use electrostatics to protect spacecraft from cosmic radiation and he asked me to lead the effort. 1/n

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Dr. Phil Metzger

@DrPhiltill

16 days

Untrue. This does touch on something related that actually happened, which people have apparently distorted and used to prop up the dumb conspiracy theory. I will explain… 1/N

Mike Gorman

@mikexgorman

18 days

NASA deleted ALL the footage and telemetry data from the moon landing … this was an amazing #JRE with Bart Sibrel

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Dr. Phil Metzger

@DrPhiltill

3 months

I could write a 50 page paper answering this :) A few points in outline form only: 1) The rocket exhaust is expanding into vacuum, so viscosity breaks down, so the gas does not obey the Navier-Stokes equation, which is the basis of CFD (computational fluid dynamics) models. /1

John F Kross

@johnfkross2

3 months

@DrPhiltill Can you elaborate on your statement that "we haven't solved the physics of blowing dust." In what manner are CFD models of lunar dust under rocket plume inadequate?

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Dr. Phil Metzger

@DrPhiltill

2 years

Contrarian perspective. I am sure there is NOBODY in this picture looking back at us. There might be beings out there looking in this direction, but they are looking at dinosaurs, or single cellular life, or a Milky Way before our Sun had formed — humans are not in their view 😞

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Dr. Phil Metzger

@DrPhiltill

4 years

Saw the most brilliant double rainbow today. It is cool how the sky is darker between the two bows and lighter inside the smaller now. This is because light that hits raindrops bounces back more in some directions than in others.

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Dr. Phil Metzger

@DrPhiltill

4 years

Best video ever. We can now deactivate the internet.

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Dr. Phil Metzger

@DrPhiltill

4 years

This is Johannes Kepler in a letter he wrote in 1610 telling Galileo that they need to do more telescopic observations of the Moon and Jupiter before spacecraft missions start visiting those planets. Yep, this conversation actually happened...in 1610 🤯

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Dr. Phil Metzger

@DrPhiltill

5 months

Christopher Nolan collided 500 main sequence stars to create a supermassive black hole for Interstellar rather than using CGI.

Historic Vids

@historyinmemes

5 months

Christopher Nolan planted 500 acres of corn for Interstellar rather than use CGI.

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Dr. Phil Metzger

@DrPhiltill

3 years

Since this Guardian writer has recycled the super-uninformed claim "we ought to be spending the money on Earth instead," it is now time to recycle the informed responses. (1) Hardly *any* money is spent on space. E.g., the US spends 4X as much on tobacco as on space. 1/n

Robert Zubrin

@robert_zubrin

3 years

“Revive the US space program? How about not” The Guardian discredits itself with another putrid article poo pooing progress.

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Dr. Phil Metzger

@DrPhiltill

4 years

Yes: the thrust will equal the mass of the EM drive times the speed you chuck it off the back of your spaceship times the number of them you chuck per second.

SPACE.com

@SPACEdotcom

4 years

Can the EmDrive actually work for space travel?

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Dr. Phil Metzger

@DrPhiltill

1 year

We used steel plates for some of the Morpheus launch locations so we weren’t tied down to places with concrete. I analyzed the heating of the sheet and showed that the heat would redistribute fast enough that it would not locally melt on the surface, and… /1

Elon Musk

@elonmusk

1 year

@SciGuySpace 3 months ago, we started building a massive water-cooled, steel plate to go under the launch mount. Wasn’t ready in time & we wrongly thought, based on static fire data, that Fondag would make it through 1 launch. Looks like we can be ready to launch again in 1 to 2 months.

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Dr. Phil Metzger

@DrPhiltill

1 year

At NASA my last federal position description (PD) was “Physicist of Launch Pad Materials.” I was the only person in the government to hold that job title (because they created it for me). I’m still kinda proud of that 😅 So yeah, the #Starship launch pad is…interesting.

Paul Byrne

@ThePlanetaryGuy

1 year

The ground under the #Starship Orbital Launch Mount, h/t @unrocket [ooof .gif]

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Dr. Phil Metzger

@DrPhiltill

4 years

To get a sense for how big the Moon is, first look at Africa. The Moon is 24.5% larger! That’s why we call it “Earth’s 8th continent”. Source: IG/

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Dr. Phil Metzger

@DrPhiltill

4 months

True story about this you will likely find interesting. Right after SpaceX started crashing rockets into barges and hadn’t perfected it yet, I met a young engineer who was part of NASA’s research program for supersonic retropropulsion. He said,… /1

Peter Hague PhD

@peterrhague

4 months

A lot of people don’t realise just how clever the reentry burn is. Your rocket engines create their own transient heat shield

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Dr. Phil Metzger

@DrPhiltill

16 days

15/ A person who has done hard work preserving old space data is @wingod . He has copied and preserved many data tapes from the older robotic missions. Congress should set some money aside to preserve all the Apollo telemetry, too. /end 🧵

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Dr. Phil Metzger

@DrPhiltill

3 years

1/n. We were discussing this comic by @xkcd while examining simulated lunar regolith, today. It came from this great piece about research by physicist Dr. Karen Daniels on why SAND PHYSICS is so dang difficult. (THREAD)

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Dr. Phil Metzger

@DrPhiltill

3 months

A bit of physics to help understand why this happens. When a lander is tipping, inertial forces push it over, while gravity pulls its feet back down flat. On the Moon, gravity is reduced by a factor of 6, but inertial forces are not. *Everything is 6 times tippier on the Moon.*

Paul Byrne

@ThePlanetaryGuy

3 months

I, uh...

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Dr. Phil Metzger

@DrPhiltill

1 year

One thing that people probably forget when building launch pads is that there is gas pressure pushing up from under the pad. Dirt has air pressure in it. If rocket exhaust finds a crack, it pressurizes the dirt under the launch pad far more. This can lift concrete slabs. /1

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Dr. Phil Metzger

@DrPhiltill

6 years

I'd like to share the story of a personal interaction I had Alan Bean, Apollo Moon-walker and artist. In 2010, I needed more information about something Alan had seen when he was on the Moon. I was researching how rocket exhaust blows soil and dust during lunar landings. /1

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Dr. Phil Metzger

@DrPhiltill

4 months

3/ “But then @elonmusk just went and tried it, and it WORKED! So NASA canceled our entire program!” 😂😂😂 The beauty is that SpaceX didn’t even have to land on the barge for this result. Just hitting the barge with the booster proved that supersonic retropropulsion worked.

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Dr. Phil Metzger

@DrPhiltill

16 days

3/ The originals had been converted to digital and this was more convenient for us to use, since we wouldn’t need reel-to-reel NTSC video equipment, so this is what we got. I had high resolution copies of all the landing videos. There was no lost video. It all exists.

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Dr. Phil Metzger

@DrPhiltill

2 months

I’m telling you guys, step by step, computing will move to space. Soon most computing will be off-Earth where it doesn’t devour Earth’s energy budget. Most of the value created by the economy will be created in space. This is just one step along the way:

emperor constantine xii

@somefoundersalt

2 months

Today I’m unveiling @AetheroSpace 63,500 satellites will enter orbit by 2030, but ground stations can’t keep up with demand We build radiation-hardened edge computers to fix that problem Our goal? Let satellites process data on orbit and automate the future of space operations

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Dr. Phil Metzger

@DrPhiltill

3 months

Imagine you built an experimental payload and it is going on a test ride to the Moon. Then the spacecraft engineers ask if they can use your *payload* to *navigate* for *lunar landing*, something never planned for, and they write a software patch in lunar orbit, and it WORKS🔥

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Dr. Phil Metzger

@DrPhiltill

4 years

I thought I would point out a few of the cool, but maybe unnoticed, phenomena that occur in this video. Here goes! ...1/n

✍️ Leonardo D'Anchiano

@HdAnchiano

4 years

Dinámica de fluidos en toda su gloria.

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Dr. Phil Metzger

@DrPhiltill

5 years

1/ I just stumbled on these pics I took 3 years ago at a public pool showing the waterfall feature. There's some awesome science in this.

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Dr. Phil Metzger

@DrPhiltill

4 years

If Salvador Dali built wind turbines

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Dr. Phil Metzger

@DrPhiltill

4 years

Books always say Saturn has such low density it could float in water. But a planet with an ocean big enough to put Saturn in would have so much gravity it would rip Saturn apart and the materials would merge into one planet. Saturn floating never makes any sense 😜

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Dr. Phil Metzger

@DrPhiltill

8 months

The power! The regolith didn’t last very long. So cool! (Sorry for the bad camera work. My eyes were on the rocket.)

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Dr. Phil Metzger

@DrPhiltill

7 months

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

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Dr. Phil Metzger

@DrPhiltill

1 year

We did see plume anomalies during ascent. Engine shutdowns are common but very few are “loss of nozzle” events. Six in one flight suggests a common cause. I’d guess it was failure of the launch pad creating ejecta that struck various bells, causing their failures during ascent.

Ezer

@EzerRatchaga

1 year

In Everyday Astronaut's stunning 8k video, it was observed that the six Raptors which failed were completely devoid of their nozzles.

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Dr. Phil Metzger

@DrPhiltill

6 years

1. Wanna hear a weird but true story? (I have a few minutes to type, so here goes). I almost lost my hearing from the lid on the tank of a toilet. Noise-Induced Hearing Loss. You wouldn't think a toilet lid could be so loud, would you? Well, I learned otherwise...

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Dr. Phil Metzger

@DrPhiltill

1 month

I'm tired of reading in the news people proclaim that starting a city on another planet is economically ridiculous when clearly they are just guessing. So I'm finally starting to write a paper on the analysis I did a few years ago that found (to my surprise) it is quite feasible.

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Dr. Phil Metzger

@DrPhiltill

16 days

2/ First I’ll tell you what I know about the videos, then the telemetry. When I analyzed the plume effects of the lunar landings, starting in the late 1990s and early 2000s, I tracked down the original data. One of the guys on my team worked with Houston to get the videos.

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Dr. Phil Metzger

@DrPhiltill

16 days

14/ The telemetry exists, but it is so hard to get that I wonder if now, even 20 years after I tried, whether anybody has spent the funds to bake those tapes, read the formats, and archive it in a more modern digital format. It may literally take an act of Congress to authorize.

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Dr. Phil Metzger

@DrPhiltill

6 months

As a friend asked today, “Have you ever seen a Mach diamond NINE METERS IN DIAMETER?!”

Max Evans

@_mgde_

6 months

Thirty. Three. Raptors. Super stoked to have captured Booster 9 and her Raptor engines in their glory this morning - the was the first time all 33 were successfully ignited with continuous burn through first stage flight. 📸 - @NASASpaceflight 📺 -

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Dr. Phil Metzger

@DrPhiltill

16 days

4/ The telemetry is more interesting. It still exists, too, but it is nearly impossible to read. When I inquired, they told me the reel-to-reel magnetic tapes were all in storage, and they could get them out for me, but the specific player for those tapes was not at KSC. Worse…

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Dr. Phil Metzger

@DrPhiltill

2 months

Wow! Having studied hundreds of videos of rocket plumes blowing craters into fluidizable surfaces, I’ll say that this interpretation is exactly correct. The plume blows a narrow deep hole into the ocean that rapidly broadens into a large “water crater”. It is the ocean.

∆lex ÐelderfiΞld 🎮🚀🟠

@Alex_ADEdge

2 months

Rewatching the final moments of Booster 10. It looks like we are actually seeing the moment of impact with the ocean in those final frames?! Altitude does read 0 as well. #SpaceX #Starship

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Dr. Phil Metzger

@DrPhiltill

1 year

I guess I need to do simulations to see how sand can fly 5 miles from a Starship launch. I did the analysis for NASA for Mars landings, and the size of particle that went farthest in that super-thin Martian air was pea gravel (~3 mm diameter) and it only goes 725 meters. /1

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Dr. Phil Metzger

@DrPhiltill

5 years

THIS IS MORE AWESOME THAN ALL THE OTHER AWESOMES! We drove from the lunar resources workshop into D.C. to see this. Look at the LOX venting! 🚀🚀🚀

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Dr. Phil Metzger

@DrPhiltill

16 days

6/ They said that I could do this if I needed the data. Then I could take the tapes to Langley where they still had one of the old Apollo-era reel-to-reel tapes so I could read the data. But then I would need to interpret the data stream. Spacecraft have multiple data formats.

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Dr. Phil Metzger

@DrPhiltill

10 months

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.)

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Dr. Phil Metzger

@DrPhiltill

7 months

I like this quote from SpaceX: “Their [FAA’s] mission is to enable safe spaceflight. We cannot give up on the safety side, but could there be a little bit more emphasis on the enable side?” /1

Eric Berger

@SciGuySpace

7 months

In a remarkably frank discussion this week, several senior SpaceX officials spoke with Ars Technica on background about how working with the Federal Aviation Administration has slowed down the company's progress. Article:

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Dr. Phil Metzger

@DrPhiltill

1 year

Having worked on and around Space shuttle tiles, I can tell you there’s a thing known as “step and gap” (important for laminar flow and heat transfer), and the tiles in this picture don’t yet demonstrate mastery of that topic (to say the least).

Chris Combs (iterative design enjoyer)

@DrChrisCombs

1 year

Notice how w each iteration we see a higher % of tiles that are a custom fit to their unique location. Was probably inevitable I know they wanted to simplify things but I’ve got a feeling the tile layout is basically gonna look like the shuttle when it’s done #starship #SpaceX

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Dr. Phil Metzger

@DrPhiltill

2 years

I’m shocked by the streamers in the ejecta. In ordinary granular splash experiments we see nothing like this. A few musings about this in a thread… /1

LICIACube

@LICIACube

2 years

Here are the first images taken by #LICIACube of #DARTmission impact on asteroid #Dimorphos . Now weeks and months of hard work are now starting for scientists and technicians involved in this mission, so stay tuned because we will have a lot to tell!

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Dr. Phil Metzger

@DrPhiltill

6 months

This is mind-blowingly cool. Continent-sized fragments of the ancient planet Theia, which collided with Earth 4.5 billion years ago to form the Moon, have been located deep within Earth’s mantle. They are STILL THERE 🤯

Qian Yuan

@qianyuan_geo

7 months

First-ever: We've identified a new astronomical object, 'Buried Planet', using SEISMOLOGY, rather than telescopes. It's a survivor of Theia, the planet that collided with Earth 4.5 billion years ago to form our Moon. See our @Nature cover paper:

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Dr. Phil Metzger

@DrPhiltill

3 years

If that signal from Proxima Centauri turns out to be aliens, it will be the only thing people in the future remember about 2020. They won’t remember all the stuff that sucked.

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Dr. Phil Metzger

@DrPhiltill

16 days

8/ To read the data you need to find out which format they were in for the period of time you are looking. Then you need the document that tells which data words are in each position of the telemetry, and how to convert the 1s and 0s to engineering units. Those documents exist…

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Dr. Phil Metzger

@DrPhiltill

16 days

7/ There is so much data on a spacecraft but only limited bandwidth in the communications channel, so they do not send all the data all the time. At different parts of the mission they use various “formats” that include only the data needed at that time.

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Dr. Phil Metzger

@DrPhiltill

16 days

5/ …because they were about 40 years old at the time, they had probably degraded. They said before you use them you have to perform a procedure to bake them so the magnetic material will re-adhere better to the tapes.

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Dr. Phil Metzger

@DrPhiltill

3 years

Can you imagine being a kid in that family trying to convince your classmates that BOTH of your parents REALLY ARE astronauts?!

Michael Sheetz

@thesheetztweetz

3 years

An astronaut family: Photos: Kim Shiflett/NASA

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Dr. Phil Metzger

@DrPhiltill

9 months

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

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Dr. Phil Metzger

@DrPhiltill

16 days

9/ in the tech library, so you have to go ask the librarian to pull them out and you have to spend hours reading them to find what you want. Then you have to read mission reports that tell what part of the mission used what format. Then you have to write software to pull out…

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Dr. Phil Metzger

@DrPhiltill

16 days

12 (When I say “the days before computers”, I mean before the engineering department had personal computers. They only had hand calculators and graph paper. It was still that way when I was first worked on the Shuttle. Of course Mission Control and the spacecraft had computers.)

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Dr. Phil Metzger

@DrPhiltill

16 days

11/ So what we did instead… we found an old-timer at JSC who had worked on the part of the telemetry we needed, and we found in his desk a plot he made on that green engineering graph paper from the days before computers. It had what we needed…

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Dr. Phil Metzger

@DrPhiltill

1 year

Well today was a good day. After 25 years researching how rocket exhaust lifts soil, I think I finally got the main story put together. I will submit this to one of the prestige journals, I guess, since I’ve never published in them but would like to at least once in my life 🙃 /1

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Dr. Phil Metzger

@DrPhiltill

16 days

10/ …the specific words you want and put them into a shorter file that you can work with for your analysis. When I considered all this, I decided it was too much work and I didn’t have enough money in my project to do all that on top of the actual analysis that I was planning.

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@DrPhiltill

16 days

13/ So none of the engineers had digital data from Apollo. It was all stored away on tapes. But we found this guy who had plotted exactly what we needed — the height of the lunar module versus time during landing. So that’s what we used.

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@DrPhiltill

2 years

😭❤️ She is headed to MIT to work on a doctorate in physics, next. Last week she was just born and was a tiny baby.

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Dr. Phil Metzger

@DrPhiltill

4 years

Well, if Mars replaces the Moon, the month will be only 26 days long and the tides will be 8.7 times higher. For example, there will 40 foot tides in NYC. Also...

XKCD Comic

@xkcdComic

4 years

Solar System Changes

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Dr. Phil Metzger

@DrPhiltill

3 years

29/ After I stopped working on this project I moved on to how rockets blow soil, space mining, and regolith physics, which turned into a lifetime career. Others continued the radiation shield effort. But I wrote one paper on this before moving on:

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Dr. Phil Metzger

@DrPhiltill

4 years

There was an employee at NASA whose actual job was to get wildlife out of the rockets & facilities. Once a raccoon got into a Space Shuttle orbital maneuvering system (OMS) pod, so they called him. He made hissing noises at the raccoon until it came running out. #animalwhisperer

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Dr. Phil Metzger

@DrPhiltill

2 months

Here’s something I think is cool in the new papers that I linked yesterday. My research group over the years has run many, many small scale experiments where a jet digs a crater against a window so we can see into it.

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Dr. Phil Metzger

@DrPhiltill

2 months

The fact that Starlink and TDRS data from Starship were both lost at the same time indicates not only that the Starship had a failure but that they had data up to the point of failure, which I think is good news since they will be able to study what happened.

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@DrPhiltill

1 year

Can someone provide the exact launch time for the Starship, down to the second? Asking because a colleague is looking at seismic data and he thinks he sees the launch. Seismic data will help determine the energy involved in the pad failure and ejection of debris. 1/2

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Dr. Phil Metzger

@DrPhiltill

2 months

This view of the reentry plasma on the flaps is stunning! Have we ever seen a view like this before?

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@DrPhiltill

2 years

BTW, the reason we need to experimentally slam a spaceship into an asteroid rather than simply *calculate* how much it will deflect the asteroid, is because regolith physics is UNSOLVED and too hard to calculate! The splash of regolith on impact determines the deflection. 1/2

CNN

@CNN

2 years

A NASA spacecraft that will deliberately crash into an asteroid has successfully launched. But the true test will come in September 2022, when the spacecraft reaches its destination, to see how it impacts the motion of a near-Earth asteroid in space.

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Dr. Phil Metzger

@DrPhiltill

3 years

From the talk I gave at the ASCE Earth & Space conference today. When you land on the Moon, your rocket exhaust is faster than lunar escape velocity and there is no atmosphere to slow down the dust you blow. We need to worry about damaging things in orbit. Short thread... /1

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Dr. Phil Metzger

@DrPhiltill

3 months

2/ When I was at NASA, one of the things I was doing was writing solicitations to industry to write physics-based code to do CFD without Navier-Stokes. There are many ways to treat the fundamental physics (the Boltzmann Transport Equation) and they all work for different…

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Dr. Phil Metzger

@DrPhiltill

7 months

Any theories on what this is? Looks like a rocket or spacecraft breaking up and burning, but I don’t know why the pieces stop at similar altitudes then move mostly laterally after that. Multiple ppl recorded it. Will repost the others next. /1

pezado.eth

@pezado_

7 months

Anyone else from San Diego see this a few minutes ago? #SanDiego #UFOs #ufotwitter

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Dr. Phil Metzger

@DrPhiltill

3 months

3/…approximations, but it is really hard to write a code that will handle the full range of conditions from dense gas inside the rocket nozzle all the way to rarefied gas on the Moon far from the rocket. 2) We don’t understand turbulence when the gas becomes rarefied.

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Dr. Phil Metzger

@DrPhiltill

4 months

This is a fun and fascinating thread. I’ll add one thought. Latif says that some objects are dynamical and move about but the “regular” planets & moons aren’t that way, but really it’s just a matter of timescales. Everything changes orbits. 1st read Latif’s thread then mine…🙂/1

Latif Nasser

@latifnasser

4 months

Last January, I noticed something peculiar in my 2yo’s bedroom that - after a year of obsessive reporting - led me to a profound cosmic revelation about what’s even possible in our universe. A 🧵.

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Dr. Phil Metzger

@DrPhiltill

4 months

2/ “At NASA, we had a big program planned to study this. We were going to start with lots of computer simulations. Then we would put a thruster on a high speed rail car and shoot the plume into the direction of travel. Then we’d drop rockets off high altitude balloons…

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Dr. Phil Metzger

@DrPhiltill

8 months

But did we?

Culture Critic

@Culture_Crit

8 months

Why did human beings stop building wonders?

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Dr. Phil Metzger

@DrPhiltill

3 years

I'm developing an algorithm to extract dust particle sizes from a series of laser scattering measurements for when rockets land on the Moon. I just plotted my data. I have to say, this is the saddest looking data I have ever seen.

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Dr. Phil Metzger

@DrPhiltill

3 months

From what I gathered, they expected they might have a challenge pointing the antennas after landing so it was not off-nominal as far as I know. And remember there are unknowns about comm systems in the lunar south polar region because… /1

Intuitive Machines

@Int_Machines

3 months

After troubleshooting communications, flight controllers have confirmed Odysseus is upright and starting to send data. Right now, we are working to downlink the first images from the lunar surface.

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Dr. Phil Metzger

@DrPhiltill

3 years

16/ This was my first experience working on an "impossible" problem, and it turned out to be Not Impossible. This influenced me to believe (now) that there are no impossible problems. We just have to find new ways of looking at problems to make them *become* possible.

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Dr. Phil Metzger

@DrPhiltill

3 years

Response: as everyone who has been paying attention already knows, space *is* about fixing Earth & the human condition, and space tourism is about creating revenue to progress the business models toward fixing these things. Literally. And that is why we are excited about it.

Mail+

@DailyMailUK

3 years

Prince William slams the billionaires' space race 🚀❌ + The Royal says they should focus on fixing Earth's problems first Read more:

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Dr. Phil Metzger

@DrPhiltill

9 months

Einstein’s paper on special relativity included *zero* references to other papers. Imagine the editor saying, “Now Dr. Einstein, I require you to add at least 20 citations to this paper so it can boost the journal’s metrics.”😆

Andrew Higgins

@A_J_Higgins

9 months

Please, please stop doing this sh_t.

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Dr. Phil Metzger

@DrPhiltill

6 years

This short video brought tears to my eyes. Wow. "Have you ever really seen the Moon?"

Have You Ever Really Seen the Moon?

A simple act becomes an awe-inspiring reminder of common humanity.

www.theatlantic.com

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Dr. Phil Metzger

@DrPhiltill

4 years

How it started: How it’s going:

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Dr. Phil Metzger

@DrPhiltill

4 months

I learned the hard way, when you want to leave your computer open so it can run physics simulations that take several hours to finish, and you have cats in the house, you have to leave it like this.

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Dr. Phil Metzger

@DrPhiltill

11 months

Partial results on the analysis of the ejecta from the SpaceX Starship launch. The visible and infrared spectra of the fine particles that rained down on Port Isobel do not match the concrete or the Fondag that was picked up on the beach. /1

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Dr. Phil Metzger

@DrPhiltill

9 months

The talk about SpaceX being sued over not hiring refugees/asylum status: I will just add that the export control laws are so onerous, difficult to implement, and horrendous in threatening destruction of your family, that I *often* think about getting out of aerospace entirely. /1

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Dr. Phil Metzger

@DrPhiltill

1 year

So I just had one of those moments that you live for as a scientist. I’ve been working for weeks on a “first principles” theory for the rate that soil erodes under a rocket. This was motivated by the sudden realization how to solve a key parameter from the reduced gravity data.

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Dr. Phil Metzger

@DrPhiltill

3 years

Just had the daily meeting with NASA (as consultant on a research project) and the only thing I can say is that NASA is kicking butt working toward an amazing future. For the past 2 weeks, every day I have seen things in physics that I have never seen before.

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Dr. Phil Metzger

@DrPhiltill

2 months

Lots of discussion today on space radiation including errors like this one. This has confused water with regolith. Using too thin a layer of *regolith* creates secondaries, increasing the dose. But using water, or PTFE (lots of hydrogen), even very thin, always reduces the dose/1

Pinboard

@Pinboard

2 months

@Irrationalactor Not unless you wrap the habitat in a shell of water several meters thick. Otherwise it actually makes the problem worse (through secondary radiation).

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Dr. Phil Metzger

@DrPhiltill

4 months

Today: former NASA administrator advocating to shut down commercial spaceflight. He earlier tried to shut down the commercial crew contract because he didn't trust SpaceX to be reliable. Also today: SpaceX launches humans into orbit in a fully commercial mission.

Eric Berger

@SciGuySpace

4 months

Mike Griffin’s Moon plan is pretty bonkers.

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Dr. Phil Metzger

@DrPhiltill

1 year

Thanks so much to the people who sent samples and pictures/videos of the particulate falling 5-6 miles from the Starship launch pad. We have analyzed the particle sizes and shapes and got an unexpected result. 1/n

Dr. Phil Metzger

@DrPhiltill

1 year

9/ If anyone can sweep up some of the sand that landed 5 miles away and send it to me, I will pay postage and will return the sample after testing along with some small thank you token (a patch?). I want to measure density, sizes, and drag forces on the particles. DMs are open!🙏

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Dr. Phil Metzger

@DrPhiltill

3 months

4/ As the path lengths of the gas molecules becomes longer between collisions of the gas molecules, it takes larger distances for them to close a loop of motion, so turbulent eddies have to become larger in diameter. (Pic source: )

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Dr. Phil Metzger

@DrPhiltill

4 years

Layers in metamorphic rocks. 🌍❤️

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Dr. Phil Metzger

@DrPhiltill

2 years

Another interesting fact: a lot of the darker, new tiles (the replacements) are located over antennas, which we sometimes used as convenient access points for airframe structural inspections between flights. /1

Andrew Rader

@marsrader

2 years

Space Shuttle heat shield tiles close up. Each is individually marked, and the darker ones are replacements which have not yet undergone re-entry.

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Dr. Phil Metzger

@DrPhiltill

1 year

22/ If the rocket doesn’t mind the shaking, then fine. But it is easy to design systems that reduce launch acoustics and give more margin back to the vehicle, so if SpaceX decided to do so then it could be done. End 🧵

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Dr. Phil Metzger

@DrPhiltill

2 months

Ok guys, the papers are now PUBLIC! This was the culmination of 27 years’ work. Links to follow. Short thread… 1/N

Dr. Phil Metzger

@DrPhiltill

3 months

I finally submitted this paper to Icarus (planetary science journal). I split it into two papers: “Erosion rate of lunar soil under a landing rocket, part 1: identifying the rate-limiting physics” and “…part 2: benchmarking and predictions.” The breakthrough was in part 1. 1/N

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Dr. Phil Metzger

@DrPhiltill

3 months

About how the lunar environment makes everything tippier… 1) I’m sure the CLPS contractors know this and designed for it. My point is that the Moon does this to your hardware, so when things go wrong (as they do) then tipping happens more often than on Earth. /1

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Dr. Phil Metzger

@DrPhiltill

3 years

25/ To write that code, we had to develop some new math to use in electric field multipole expansions including image charge effects. To this day this is one of the things I am most happy about doing, even though it has not been cited much. (full paper: )

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Dr. Phil Metzger

@DrPhiltill

6 years

40/40 My hope is that every painting he had in his heart made it onto his canvas before time ran out. Though I won't walk on the Moon, I hope I can see colors like Alan did everywhere I go. And I hope we'll share his passion & focus to keep painting--in our own ways--to the end.

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Dr. Phil Metzger

@DrPhiltill

6 months

I meant this literally, not hyperbolically. We used equations for volcanic caprock explosions to explain the 90 m/s ejecta velocity. “Starship's first liftoff toward space created the equivalent of a volcanic eruption in the launchpad, physicist finds”

Starship's first liftoff toward space created the equivalent of a volcanic eruption in the launch...

SpaceX's Starship rocket atop its Super Heavy booster is the most powerful rocket in history, capable of generating the same force as a volcanic eruption.

www.businessinsider.in

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Dr. Phil Metzger

@DrPhiltill

26 days

NASA now building a flight-ready lunar excavator for a resource utilization pilot plant (not a demonstration — the actual pilot plant) on the Moon.

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Dr. Phil Metzger

@DrPhiltill

3 years

2/ The problem with using electrostatics to shield a spacecraft is that space is filled with both positive and negative charged particles, so if you use a positive field you attract the negative particles, and vice versa. Then,...

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