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Today's "Daily Launch" from AIAA finally brings up the heat shield issue facing Artemis-2 as it heads to re-entry. The link was to a Scientific American article of some kind. Not all the supposed facts quoted in it were correct, but the concern over char cracking leading to the shedding of chunks of char was correctly pointed out.
Myself, I think the odds are good that the crew will come home just fine. Where I differ with NASA is that I think the same damage seen on Artemis-1 will happen to Artemis-2's heat shield, despite switching to a non-skip, single heating pulse entry. It might be less than what happened to Artemis-1, or it might not. But if ANY chunks at all get shed, then NASA was wrong and I was right!
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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This post is reserved for a set of files GW Johnson sent by email on Tuesday 2026/04/21
I'll return to this post later today, Wednesday 2026/04/22
Work plan:
1) three pdf's in HeatShieldArtemisII folder to Dropbox
The three pdf's were stored in Dropbox
2) Link three pdf's from Dropbox to this post
https://www.dropbox.com/scl/fi/sp0kxa1o … w1mzq&dl=0
Above is Entry By Hand Article using spreadsheet from Orbits Course
https://www.dropbox.com/scl/fi/udi4mzuk … 0ptpm&dl=0
See notes below for content
https://www.dropbox.com/scl/fi/auanvzc5 … nnabe&dl=0
Study of Orion heat shield after Artemis II flight
3) Add text from email to explain links
Test from email:
First: there is "Entry By Hand Article.pdf", which shows exactly how to
use my entry spreadsheet and do really interesting things with it. There
are slides and presentation notes for this.Second: there is "Entry Study.pdf", which shows results and comparisons
for a small probe with either a conical heat shield or a blunt heat
shield, at Earth from LEO and lunar return, and at Mars from direct entry
off a fast interplanetary trajectory. All of that gets compared to an
Apollo returning from the moon, or from low circular orbit, at Earth.There are slides and presentation notes for this, too.
Third: there is "Quick First Look at Orion.pdf, where I ran a spread of
entry angles for an Orion lunar return, trying to figure out how to use my
simple tools to at least bound what Artemis-2 really just did. No slides
yet, but there will be.If you want to post any of this stuff on the forums, be my guest.
Updates completed 2026/04/22 at 23:27 UTC
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This post offers a link to a document prepared by GW Johnson:
https://www.dropbox.com/scl/fi/s3r092rt … scnaw&dl=0
Preliminary Evaluation of Artemis II heat shield performance.
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This is what a post to LinkedIn by GW Johnson looks like:
<snip>
Gary Johnson’s picture
Gary Johnson posted: Entry Model Heat Shield Pressure This is the second of three postings about…
<snip>
GW Johnson is posting regularly on the Wordpress blog, occasionally on YouTube, occasionally on NewMars and lately on LinkedIn.
If anyone spots additional coverage of GW Johnson topics, please post a report here.
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Todo list for updates for GW Johnson:
1) spreadsheet update
Status: saved local
Todo: Dropbox and link to forum <done>
2) new pdf
Status: saved local
Todo: Dropbox and link to forum <done>
PDF document: Launch to Low Earth Orbit Study - Presentation
https://www.dropbox.com/scl/fi/3q2p3aj4 … 9h40b&dl=0
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For GW Johnson re Starship flight ...
There were a couple of nice touches by the Communications Team ..
1) There was a drone flying at the target site in the Indian Ocean.
It showed the Starship falling over slowly and then exploding with plenty of fireworks action
2) The cameras on the deployed simulated satellites showed the Starship in flight.
Naturally we saw the ** top ** of the Starship, since the deployment bay door was on top of the vehicle.
The views from inside the cargo bay were well done, including views from overhead, beside the slider, and aft of the slider.
3) The camera attached to one of the fins gave us a nice sense of the movement of the fin in flight.
According to reports there were 52 cameras on this mission, and perhaps more footage will become available.
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GW Johnson send me a link to a YouTube video about heat shields... The video is long because it covers a variety of heat shields, and it repeats itself quite a bit. Details are abundant. On balance I think it was worth my time. I played it without audio. GW played it with audio and reported that the AI voice mispronounced a few words.
URL here: I misplaced the link. I'll try to find it and will ask Dr. Johnson to send it again.
And! Here it is: https://www.youtube.com/watch?v=S5xuB5DVS8U
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For GW Johnson re post by HOP...
http://newmars.com/forums/viewtopic.php … 63#p239663
Your post seems to miss the point.... HOP was not talking about space elevator to the surface of Mars.
He was talking about passing mass between the Moons.
This is an advanced concept in orbital mechanics.
It will be interesting to see if you can recreate his calculations.
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This post contains an opinion piece by GW Johnson.
It starts from the post by Calliban about the recent SpaceX IPO,. and ends up offering a vision for a fully realized transportation system for Earth/Mars.
I regret not knowing how to reformat the file so that the arbitrary carriage returns from email are removed. There may be an easy way to do that, but if there is and I knew about it, I've forgotten.
Myself, I see little direct connection between what happens in the
"financial world" of stock trading, and what happens in the "real world"
of actually building hardware and doing things with it. The one is about
obtaining money, the other about building hardware. The actual connection
is only that hardware is expensive. Politics (which utterly controls and
permeates most of NASA) usually impairs both worlds (but especially the
real world), to the point of stopping or damaging a lot of real-world
hardware efforts. The politicians want for themselves the money needed to
build the hardware, simple as that. That assessment may be pessimistic,
but it is realistic.The original Mars mission plans were drawn up during the Apollo moon
mission efforts. They were not carried out because the cost was very high
and politics would not allow it. The very same pessimistic
politics-afflicted situation has prevailed for over half a century since
then, and it shows up in the per-launch price of SLS-Orion. After half a
century doing nothing but LEO stuff, NASA is proving to be far less
capable about going back to the moon at all, much less efficiently., than
it was in the 1960's.That leaves private outfits like Musk. Personally, he is far better at the
money, than he is about the hardware. I say that because SpaceX has ZERO
experience malking rough field landings with ANY of its rockets, and TESLA
is still afflicted with its self-driving software that kills people,
violent battery fires, and some other recalls here and there that should
not be. Plus, for a while there during the first Starship test flights,
he kept getting into trouble with the FAA by violating his launch license
terms, since he doesn't believe that other people's rules apply to him.The only strategic thing that Musk did that was right, was
understanding that costs to go to the moon and Mars must be
lowered drastically, in order to get the politicians out of the way,
since their only excuse not to go, was cost. A lot of others realized
that too, but Musk was the first one to come up with enough money to try
doing it.I think his Starship/Superheavy will be the same leap forward as a
surface-to-LEO transport that his Falcon-9 and Falcon-Heavy were before.
Getting first stage reusability by flying it back and landing has been a
huge success, enabled entirely by the low return speeds allowing entry
without a heat shield. Getting upper stage reusability has been very hard
indeed, because now the upper stage must be a fully-qualified entry
vehicle, plus it must have a means of landing, and those very seriously
compromise the design! Which inherently means a refueled Starship going
outside LEO is not the best design for those beyond-LEO jobs, although it
can do them! Plus, SpaceX has zero experience landing things on rough,
soft ground. Their Starship design so far reflects nothing credible yet,
regarding making landings on the moon or Mars.Going to Mars (and back) inexpensively requires 9 transportation
infrastructure elements: (1) low-cost surface-to-LEO heavy-lift transport
(we are getting there!), (2) low-cost surface to LMO modest-lift transport
(does NOT yet exist!), (3) elliptic departure/arrival at Earth using tug
assist, as reusable stage designs that only fly in space (does not yet
exist but very soon could), (4) the Earth station in LEO that assembles
and fuels interplanetary vehicles, and refuels the tugs (does not exist,
but most certainly could), (5) a proper orbit-to-orbit transport that only
flies in space, but that can be refueled and reused (and if crewed provide
both radiation protection and artificial gravity), which as yet DOES NOT
EXIST, but it certainly could, (6) elliptic departure/arrival at Mars
using tug assist, as reusable stage designs that only fly in space (does
not yet exist, but very soon could), (7) the Mars station in LMO that
services and fuels interplanetary vehicles, and refuels the tugs based
there (does not exist but certainly could), (8) propellant manufacturing
capability on Earth (already long-established), and (9) propellant
manufacturing capability on Mars (DOES NOT YET EXIST).You can get started at Mars with only items (1), (3), (4), (5), and (8),
aimed initially at establishing item (9), and then adding items (2), (6),
and (7). Most of the same things work for the moon, except that the
vehicle making the voyage from LEO to LLO need not be
interplanetary-capable, and if crewed, need not provide artificial
gravity, simply because the flight time is mere days. The Gateway halo
orbit about the moon was NASA's version of elliptic departure and arrival
at the moon, except they botched it by (1) compromising to an unstable
orbit trying get SLS/Orion into it with the propellant to return, and (2)
they failed to put the station in LLO, leaving it on the ellipse where the
surface is very hard to reach.Bear in mind that the vehicles used in items (1), (2), (3) (5), and (6) all
have vastly-different and conflicting design requirements. You do NOT want
to try to perform more than one vehicle function with any one vehicle
design, it will be needlessly too heavy, inherently. Adding greatly to
expense. And if it gets expensive, the politicians will stop you from
trying, as they have been doing for half a century now.Bear also in mind that the tank farm function of the LEO and LMO stations
(or any LLO station), items (4) and (7), require propellant transfer in
zero-gee without ullage thrusts or accelerations. For storables, that
already exists in the form of bladdered taks with the bladders squeezed by
modest gas pressure. For cryogenics, that capability only exists as
orbit-altering ullage thrusts or accelerations, although I have come up
with the vane tank as a likely-viable-in-the-short-term alternative,
meeting all the requirements for a tank farm at a station whose orbit MUST
NOT BE ALTERED by every single transfer operation.If you want to post this email as an evaluation on the forums, be my
guest. I may try to create a slide show out of this. It's a good outline
for one.GW
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