David S. F. Portree
@dsfpspacefl1ght.bsky.social
history guy, science writer, educator, map librarian, archivist, 57 yrs a space exploration nut, ex-NASA, ex-US Geological Survey, now doing local history among the pines in Flagstaff AZ USA
Save NASA space science
https://spaceflighthistory.blogspot.com
Save NASA space science
https://spaceflighthistory.blogspot.com
Is anyone out there used to explaining the concept of "gravity losses" in the context of departure from orbit around a planet?
If so, I'd be delighted to learn how you explain it. I've been having a rough time of it - don't want to get it wrong.
If so, I'd be delighted to learn how you explain it. I've been having a rough time of it - don't want to get it wrong.
December 7, 2025 at 3:48 PM
Is anyone out there used to explaining the concept of "gravity losses" in the context of departure from orbit around a planet?
If so, I'd be delighted to learn how you explain it. I've been having a rough time of it - don't want to get it wrong.
If so, I'd be delighted to learn how you explain it. I've been having a rough time of it - don't want to get it wrong.
The San Francisco Peaks from the Northern Arizona University campus, Flagstaff, Arizona, 25 November 2025.
November 30, 2025 at 6:55 PM
The San Francisco Peaks from the Northern Arizona University campus, Flagstaff, Arizona, 25 November 2025.
Introduce yourself with four spaceships.
November 26, 2025 at 4:19 PM
Introduce yourself with four spaceships.
Here's an AIR & SPACE SMITHSONIAN article I wrote in 1998, which I scanned recently for another purpose, but I might as well share it here. It is just four pages, which means it fits nicely.
Sorry to report that the efforts reported did not lead to a Mars space suit (or at least they haven't yet).
Sorry to report that the efforts reported did not lead to a Mars space suit (or at least they haven't yet).
November 23, 2025 at 4:38 PM
Here's an AIR & SPACE SMITHSONIAN article I wrote in 1998, which I scanned recently for another purpose, but I might as well share it here. It is just four pages, which means it fits nicely.
Sorry to report that the efforts reported did not lead to a Mars space suit (or at least they haven't yet).
Sorry to report that the efforts reported did not lead to a Mars space suit (or at least they haven't yet).
The NASA Manned Spacecraft Center minimum-energy crewed Mars mission study (1968-69) post is coming along well. I got bogged down in the math for a while, until I realized that nearly all of it is approximations. They lacked data sufficient to know what would really work.
Now I am free and writing.
Now I am free and writing.
November 23, 2025 at 3:25 PM
The NASA Manned Spacecraft Center minimum-energy crewed Mars mission study (1968-69) post is coming along well. I got bogged down in the math for a while, until I realized that nearly all of it is approximations. They lacked data sufficient to know what would really work.
Now I am free and writing.
Now I am free and writing.
My daughter & I used to build lots of big LEGO kits (see below). I mostly stopped as she entered her LEGO "dark age," gifted most of our LEGO to a school. Since I started this "LEGO as therapy" thing, her interest has revived a bit - we built the LEGO orrery and a couple of small LEGO Botanicals.
November 22, 2025 at 5:51 PM
My daughter & I used to build lots of big LEGO kits (see below). I mostly stopped as she entered her LEGO "dark age," gifted most of our LEGO to a school. Since I started this "LEGO as therapy" thing, her interest has revived a bit - we built the LEGO orrery and a couple of small LEGO Botanicals.
I'll go out on a limb here and declare that the new blog post, all about the NASA Manned Spacecraft Center's crewed minimum-energy Mars mission study (1967-1969), will be posted by early December.
I anticipate that I will be run over by a bus sometime between now and then. Or struck by lightning.
I anticipate that I will be run over by a bus sometime between now and then. Or struck by lightning.
November 9, 2025 at 3:12 PM
I'll go out on a limb here and declare that the new blog post, all about the NASA Manned Spacecraft Center's crewed minimum-energy Mars mission study (1967-1969), will be posted by early December.
I anticipate that I will be run over by a bus sometime between now and then. Or struck by lightning.
I anticipate that I will be run over by a bus sometime between now and then. Or struck by lightning.
I am not yet ready to tempt fate by declaring a deadline for my next blog post - but it will look at a NASA Manned Spacecraft Center study of a minimum-energy crewed Mars landing mission that was posed as an alternative to the crewed flyby missions that briefly became the rage in 1966-1967 period.
November 2, 2025 at 7:00 PM
I am not yet ready to tempt fate by declaring a deadline for my next blog post - but it will look at a NASA Manned Spacecraft Center study of a minimum-energy crewed Mars landing mission that was posed as an alternative to the crewed flyby missions that briefly became the rage in 1966-1967 period.
27 years ago today - Halloween 1998 - my late wife and I wore our best Halloween costumes ever.
We had a small ceremony at Lowell Observatory in Flagstaff, Arizona, near the Clark Telescope dome Percy Lowell used to map canals on Mars.
We had a small ceremony at Lowell Observatory in Flagstaff, Arizona, near the Clark Telescope dome Percy Lowell used to map canals on Mars.
October 31, 2025 at 3:22 PM
27 years ago today - Halloween 1998 - my late wife and I wore our best Halloween costumes ever.
We had a small ceremony at Lowell Observatory in Flagstaff, Arizona, near the Clark Telescope dome Percy Lowell used to map canals on Mars.
We had a small ceremony at Lowell Observatory in Flagstaff, Arizona, near the Clark Telescope dome Percy Lowell used to map canals on Mars.
It would be fun to write an alternate history in which the post-Apollo space program would be based on Apollo/Saturn technology & experience - and then ask people to identify the bits I made up (as opposed to the bits based on real plans from the 1960s/1970s).
October 26, 2025 at 7:46 PM
It would be fun to write an alternate history in which the post-Apollo space program would be based on Apollo/Saturn technology & experience - and then ask people to identify the bits I made up (as opposed to the bits based on real plans from the 1960s/1970s).
I have restarted work on the GE NEP crewed Mars mission post. After all the turmoil this past month, it's like meeting with an old friend.
My goal is to finish the post by Halloween.
My goal is to finish the post by Halloween.
October 5, 2025 at 3:20 PM
I have restarted work on the GE NEP crewed Mars mission post. After all the turmoil this past month, it's like meeting with an old friend.
My goal is to finish the post by Halloween.
My goal is to finish the post by Halloween.
We've reached Zero Hour of our move, so a quick reply now - more soon.
Glad you recommend the Princeton Field Guides - I hoped they were as good as they seem! Here are mine.
I've followed dinobirds for a while, but not in a focused way (more in a "science writer keeping tabs on a hot field" way).
Glad you recommend the Princeton Field Guides - I hoped they were as good as they seem! Here are mine.
I've followed dinobirds for a while, but not in a focused way (more in a "science writer keeping tabs on a hot field" way).
September 26, 2025 at 3:05 PM
We've reached Zero Hour of our move, so a quick reply now - more soon.
Glad you recommend the Princeton Field Guides - I hoped they were as good as they seem! Here are mine.
I've followed dinobirds for a while, but not in a focused way (more in a "science writer keeping tabs on a hot field" way).
Glad you recommend the Princeton Field Guides - I hoped they were as good as they seem! Here are mine.
I've followed dinobirds for a while, but not in a focused way (more in a "science writer keeping tabs on a hot field" way).
Just walked my 1:100-scale Saturn V model to the new apartment, making crawler/transporter noises all the way. No way I was going to take that apart and put it in a box - each time I do the connections get "looser." I think the walk more or less scales to the distance between the VAB and Pad 39A.
September 25, 2025 at 12:32 AM
Just walked my 1:100-scale Saturn V model to the new apartment, making crawler/transporter noises all the way. No way I was going to take that apart and put it in a box - each time I do the connections get "looser." I think the walk more or less scales to the distance between the VAB and Pad 39A.
Here are the WVB gliders. That's the Bono glider
September 20, 2025 at 2:47 PM
Here are the WVB gliders. That's the Bono glider
Oh boy oh boy oh boy oh boy, new books! Often when I say I have some"new books" I mean "new to me" - I buy a lot of used books. These are really truly hot off the presses (or warm out of the warehouse).
And not a moment too soon. I *needed* some new new books.
And not a moment too soon. I *needed* some new new books.
September 17, 2025 at 12:54 AM
Oh boy oh boy oh boy oh boy, new books! Often when I say I have some"new books" I mean "new to me" - I buy a lot of used books. These are really truly hot off the presses (or warm out of the warehouse).
And not a moment too soon. I *needed* some new new books.
And not a moment too soon. I *needed* some new new books.
GE NEP study blog post update: I am writing about ion drive right now. I discovered that my understanding of it was not as good as I thought.
I also am cutting back some on writing about discrepancies between the volumes of the study report. It was boring. I've picked some that are representative.
I also am cutting back some on writing about discrepancies between the volumes of the study report. It was boring. I've picked some that are representative.
September 9, 2025 at 2:49 AM
GE NEP study blog post update: I am writing about ion drive right now. I discovered that my understanding of it was not as good as I thought.
I also am cutting back some on writing about discrepancies between the volumes of the study report. It was boring. I've picked some that are representative.
I also am cutting back some on writing about discrepancies between the volumes of the study report. It was boring. I've picked some that are representative.
These days I am always cutting down on my stuff. Here's the current bookcase arrangement - I had three bookcases like this, now I am down to two.
And, yes, I am a big old nerd.
And, yes, I am a big old nerd.
September 9, 2025 at 2:20 AM
These days I am always cutting down on my stuff. Here's the current bookcase arrangement - I had three bookcases like this, now I am down to two.
And, yes, I am a big old nerd.
And, yes, I am a big old nerd.
This past week or so I've had lots of commitments, so I've made little progress on the GE NEP crewed Mars mission post. Tomorrow I'll get back to it. I have a medical thing on 9/19, so my goal is to finish before that. Really familiar with the report and supporting docs now, so should be no problem.
September 1, 2025 at 11:52 PM
This past week or so I've had lots of commitments, so I've made little progress on the GE NEP crewed Mars mission post. Tomorrow I'll get back to it. I have a medical thing on 9/19, so my goal is to finish before that. Really familiar with the report and supporting docs now, so should be no problem.
2/ Only the LASTS summary volume is available. It says that Mariner IV Mars atmosphere data required that their MEM crew lander design be "rearranged," but it doesn't say how. The 1966-67 study almost ignores Mariner IV, opting for an unworkable "M2-F2" MEM that could fit atop a Saturn V easily.
August 23, 2025 at 5:15 PM
2/ Only the LASTS summary volume is available. It says that Mariner IV Mars atmosphere data required that their MEM crew lander design be "rearranged," but it doesn't say how. The 1966-67 study almost ignores Mariner IV, opting for an unworkable "M2-F2" MEM that could fit atop a Saturn V easily.
I've been trying to find info on the Mars Excursion Module crew lander in the GE Low-Acceleration Space Transportation Systems (LASTS) study (1964-66), the immediate predecessor of the GE NEP crewed Mars mission study (1966-67) I am writing about now. 1/
August 23, 2025 at 5:11 PM
I've been trying to find info on the Mars Excursion Module crew lander in the GE Low-Acceleration Space Transportation Systems (LASTS) study (1964-66), the immediate predecessor of the GE NEP crewed Mars mission study (1966-67) I am writing about now. 1/
Not sure if my fuzzy blowups add anything, so here are three more images: L to R they are Voyager (the original Voyager, which was a Mars/Venus spacecraft), early Viking, and the Viking 1 launch.
August 21, 2025 at 1:47 AM
Not sure if my fuzzy blowups add anything, so here are three more images: L to R they are Voyager (the original Voyager, which was a Mars/Venus spacecraft), early Viking, and the Viking 1 launch.
Fifty years since the Viking 1 launch (20 August 1975).
Images show (very) preliminary Viking landing sites (c. 1970).
#Mars #Viking1 #maps #spaceflight
Images show (very) preliminary Viking landing sites (c. 1970).
#Mars #Viking1 #maps #spaceflight
August 21, 2025 at 1:29 AM
Fifty years since the Viking 1 launch (20 August 1975).
Images show (very) preliminary Viking landing sites (c. 1970).
#Mars #Viking1 #maps #spaceflight
Images show (very) preliminary Viking landing sites (c. 1970).
#Mars #Viking1 #maps #spaceflight
Off to the library to spread out all my papers and notes concerning the GE NEP crewed Mars mission study. They don't all fit in my book bag any more.
I found that the Mars study is connected to a GE study of a robotic NEP lunar logistics spacecraft. I have that study; possible blog post candidate?
I found that the Mars study is connected to a GE study of a robotic NEP lunar logistics spacecraft. I have that study; possible blog post candidate?
August 20, 2025 at 3:24 PM
Off to the library to spread out all my papers and notes concerning the GE NEP crewed Mars mission study. They don't all fit in my book bag any more.
I found that the Mars study is connected to a GE study of a robotic NEP lunar logistics spacecraft. I have that study; possible blog post candidate?
I found that the Mars study is connected to a GE study of a robotic NEP lunar logistics spacecraft. I have that study; possible blog post candidate?
Working gradually through the GE NEP crewed Mars mission 16+-year development program toward the actual Mars mission in 1986-1987.
Today's conundrum: report says sea water in reactor (result of launch failure) won't lead to fission, then says water-filled reactor would be "slightly supercritical."
Today's conundrum: report says sea water in reactor (result of launch failure) won't lead to fission, then says water-filled reactor would be "slightly supercritical."
August 17, 2025 at 5:08 PM
Working gradually through the GE NEP crewed Mars mission 16+-year development program toward the actual Mars mission in 1986-1987.
Today's conundrum: report says sea water in reactor (result of launch failure) won't lead to fission, then says water-filled reactor would be "slightly supercritical."
Today's conundrum: report says sea water in reactor (result of launch failure) won't lead to fission, then says water-filled reactor would be "slightly supercritical."
GE NEP crewed Mars expedition landing sites (using old names):
Syrtis Major
Meridiani Sinus
Solis Lacus
Mare Sirenum
All popular sites for planners because they were dark telescopic features IDed with biology. Study dates to 7/1967, so Mars knowledge needed to choose sites just wasn't there yet.
Syrtis Major
Meridiani Sinus
Solis Lacus
Mare Sirenum
All popular sites for planners because they were dark telescopic features IDed with biology. Study dates to 7/1967, so Mars knowledge needed to choose sites just wasn't there yet.
August 10, 2025 at 7:08 PM
GE NEP crewed Mars expedition landing sites (using old names):
Syrtis Major
Meridiani Sinus
Solis Lacus
Mare Sirenum
All popular sites for planners because they were dark telescopic features IDed with biology. Study dates to 7/1967, so Mars knowledge needed to choose sites just wasn't there yet.
Syrtis Major
Meridiani Sinus
Solis Lacus
Mare Sirenum
All popular sites for planners because they were dark telescopic features IDed with biology. Study dates to 7/1967, so Mars knowledge needed to choose sites just wasn't there yet.