GW Johnson Postings and @Exrocketman1 YouTube videos

tahanson43206 · 2024-12-13 13:46:28

This post is for a new study by GW Johnson on NERVA style engines for Space Tug application:

https://www.dropbox.com/scl/fi/9yn0e6ey … ytejm&dl=0

(th)

RGClark · 2024-12-13 16:56:57

GW Johnson wrote:

The links work fine.
But if you read the article, you see that I did not do this study for using a tug with Artemis-2 in any way. NASA is going to fly that one with the bad heat shield, that much is clear.
Actually, since the Orion capsule is not reusable, I don't see much usefulness for trying to slow it into orbit coming back from the moon or anywhere else. It'll have a "fixed" heat shield from Artemis-3 onward, and the odds favor success flying with the bad one on Artemis-2, although the probability of a fatal burn-through is not as close to zero as it ought to be.
I did the study to find out what might be possible in the near term. For the orbital data I used, getting onto an interplanetary trajectory at 11.5 km/s requires 3.7 km/s dV from LEO at 7.8 km/s, unassisted. The tug could get it to 10.9 km/s and subsequently be recover itself from an ellipse apogeeing near the moon's orbit. The interplanetary craft dV from that tug assist point is only 0.6 km/s! Tug-assisted departure makes a big difference!
I think Starship might actually have its flap burn-through problem solved, and its heat shield pretty much determined, and also have demonstrated propellant transfer from 1 vehicle to another, in about a year, which is very near-term. That means a tug modification could be flying not that long afterward. And the mass capacity it could fling onto hyperbolic departure is astonishing: just short of 500 metric tons or thereabouts. Arrivals, not so much: nearer only 175 tons.
The real long pole in the tent is not modifying Starship or some other upper stage to be used as a space tug, it is having a good facility in LEO to assemble interplanetary payloads and then dock tugs to them, using remote-operated mechanical arms, plus a ready means and depot from which to refuel the tugs and fuel the interplanetary craft.
That won't happen on a 2-year timescale! If Gateway gets built at the moon, the assembly and propellant depot facility in LEO will never get built. There is not enough $ to do both.
But with a tug assisting departures and maybe arrivals, why would we need Gateway? THAT is the really telling question no one is asking.
GW

Does your proposal require multiple orbital refuelings?

Robert Clark

GW Johnson · 2024-12-14 15:08:53

Bob:

Short answer about refueling flights: yes, but indirectly, from a depot that must be kept filled.

Starship carrying payload has only enough propellant left aboard after reaching LEO to effect a deorbit and a landing. Unrefueled, it can go NOWHERE else. The same would be true of any other orbital transport vehicle, whether partly or fully reusable.

Any sort of craft headed for low Mars orbit must depart from LEO, correct its course, and arrive in LMO. Without a tug, LEO departure requires at least 3.7 km/s (for Hohmann transfer), probably more (if you want to go faster), with course correction around 0.2 km/s and LMO arrival somewhere near 2 km/s. That's about 5.9-ish or more km/s just to get to LMO one-way.

A tug assist to leave LEO reduces that requirement on the interplanetary vehicle to something like 0.6 to perhaps 1 km/s (faster than Hohmann), plus the same correction and LMO arrival. That puts the 1-way dV nearer 2.8 to 3.2 km/s, a substantial reduction. That opens the door to a possible return from LMO to LEO, with things we already know how to build.

That's an important improvement! You do it with a tug vehicle that remains in the ellipse after releasing the interplanetary vehicle, at the ellipse perigee where speed relative to the Earth is highest. The tug can then return to LEO and get refueled there, which is easiest to do in low eastward circular. That's why an orbital assembly facility and refueling depot makes sense. Accumulate the propellants over time between interplanetary missions, then use it when you need it to mount one.

Starship is not primarily an interplanetary vehicle, despite what Musk claims. It is a large transport to LEO and back that is intended to be fully reusable. You can misuse it by refueling it to go elsewhere, but you WILL refuel it to go anywhere else! Nobody else has a vehicle yet that meets that reusable orbit transport definition, or to go anywhere else, but if they did, the VERY SAME refueling restrictions would apply. Everybody has to obey mother nature's rules.

The refueling requirements thing in LEO if you want to go anywhere else is EXACTLY why an assembly facility and propellant depot in LEO makes so much good sense! NASA failed to build one (the ISS is NOT such a facility!!!), because government bureaucracies micromanaged by congressional politicians are actually rather brain-dead, as we all know quite too well.

GW

Last edited by GW Johnson (2024-12-14 15:15:29)

tahanson43206 · 2024-12-15 18:46:01

This post is intended to hold three new updates from GW Johnson.

They are all in pdf form so I'll save them in Dropbox and link them here.

Text by email is:

There's a posting on my "exrocketman" site titled "Tug Assisted Arrivals and Departures", posted there 12-1-2024, for which I already sent you the document to post for the forums. The link to it is in meta new mars/GW Johnson postings, in post number 465. I have since added two updates so far. Those are already on "exrocketman", and the two updates are the first two pdf files attached here. The first one is "update elliptic.pdf", which shows that more exact orbital data made little difference to the results I had found. The second one is "second update for posting.pdf", which adds a basic departure tug sizing study of what different propellants could be used, to include the old NERVA nuclear thermal.
<snip>
The enabling facility in LEO is a space station with combined assembly and propellant depot refueling functions. I came up with a way just to spin the fluid within the tank for ullage, and not have to spin the whole tank. It makes cryogenic transfers much easier and safer, with no undock and redock or vehicle spin-up/spin-down operations. That will be my February 2025 "exrocketman" posting, and my records indicate I have not sent that one to you for posting on the forums. So that pdf file is the third one attached, being "Vehicle Assembly and Refueling Facility in LEO.pdf".

Vehicle Assembly
https://www.dropbox.com/scl/fi/wec3tukl … s98qj&dl=0

Update Elliptic
https://www.dropbox.com/scl/fi/zr5nw1cg … nl1ci&dl=0

Second update
https://www.dropbox.com/scl/fi/bmyndufx … llwrs&dl=0

(th)

tahanson43206 · 2024-12-15 18:59:31

The Waiting Room is open at 00:59 UTC

tahanson43206 · 2024-12-18 12:02:45

For GW Johnson re post in Orbital Mechanics: https://newmars.com/forums/viewtopic.ph … 30#p228630

Your evaluation of the work of the person kbd512 found on the Internet suggests to me that the person kbd512 found might be interested in your work on Space tugs, Orbital refueling and maintenance stations, deep space exploration, Mars landing of 40 ton payloads, and other subjects.

We only have one member in your specialty, at the moment, and it would be terrific to have two, if the two personalities could get along. However, human males tend to be competitive, and unwilling to listen to others, so chances are no better than 50-50 that such a combination would work.

(th)

tahanson43206 · 2024-12-18 19:19:04

This post is intended to hold a link to another update of GW's work on Space Tugs.

https://www.dropbox.com/scl/fi/nnrqo5n6 … fd08r&dl=0

This is the third update to the original title:

I have finished the third update for the "Tug-Assisted Arrivals and Departures" article posted 12-1-2024 on "exrocketman". I just added that update today. It looks at using the departure sized tugs for arrivals, at reduced payload. This is the LEO-ellipse stuff, but not the lunar-directed ellipse stuff. That is more challenging, because of the LLO entry and departure burns.

Thanks to Oldfart1939 for a recent question about refueling. This is a good opportunity for me to remind GW I'm hoping he will take another look at the spinLaunch Hypersonic Frisbee suggestion I offered, to try to overcome problems associated with the original bullet shaped projectile. The Hypersonic Frisbee has the potential to carry more payload, and to have more potential for re-usability, since it could (potentially) fly itself back to it's home base due to it's aerodynamic shape.

In a recent Google Meeting, kbd512 argued for use of liquid fuel rocket technology to propel the Hypersonic Frisbee to LEO after it reaches the peak of the toss from the SpinLaunch swingarm. The argument was strengthened by the proposition that the vehicle would be carrying LOX and LH2 for the refueling station.

The whole point of the SpinLaunch concept is to provide lower cost service than spaceX will provide. SpaceX is going to be scrubbing costs to try to achieve the goal of using nothing but propellant for launches, and re-using everything else. It appears that there may be some unavoidable costs for expendable components such as the stage separation ring that is presently part of the SuperHeavy/Starship combination. But even that may go away if SpaceX finds a way to protect that component from damage.

(th)

tahanson43206 · 2024-12-21 13:47:53

This post is intended to hold a link to an image about the flight regime of the X-15.

The subject of winged flight toward space came up recently (December of 2024) when PhotoBytes provided an update on a concept for a winged vehicle able to fly in space, if it can get there.

Link goes here >>>

(th)

tahanson43206 · 2024-12-27 18:51:40

This post is intended to hold a pair of images created by GW Johnson in hot pursuit of the Space Tug concept, applied to the Mars landing problem.

NewMars readers may recall that GW investigated the idea of using foldout cargo pods for landing. The idea was inspired by some of Void's writing. The fold-out pods would have looked a bit like the landing legs of Falcon 9.

In the end, GW was unable to make all the variables line up.

In this latest version, the idea is to use a heat shield (like everyone else) but the difference is to (somehow) fold the heat shield back from in front of the engines to perform braking as the vehicle nears the ground, and then hover/landing. This particular vehicle is designed to stay on Mars after it delivers it's cargo, so the engines and other components would potentially be available for salvage.

Other components would include what remains of the heat shield, which would (most likely) contain valuable hydrogen combined with carbon. The material could be used as insulation, since Mars settlers will need plenty of it.

The material of which the lander is made would include a fair amount of high quality metal.

Depending upon how GW designs the vehicle, the frame and hull could be adapted for a variety of purposes on the ground.

(th)

tahanson43206 · 2025-01-02 16:24:04

GW Johnson notified me by email that an article about Space Tugs is now available at his exrocketman blog site:

https://exrocketman.blogspot.com/

NewMars members should have no difficulty following the presentation.

(th)

kbd512 · 2025-01-02 23:04:37

GW,

It would be nice to see what the numbers look like using Raptor-3's 380s vacuum Isp and thrust.

GW Johnson · 2025-01-03 10:20:36

I used 379, which is what they had actually been achieving with Raptor-2.

GW

tahanson43206 · 2025-01-03 13:47:02

For GW Johnson re index to publications ...

Thanks for the reminder that you had already "published" the Space Tug article here in the forum.

As of today, I get the impression the NewMars forum does not compare favorably to the exRocketman blog which runs on Wordpress.

I decided to visit blogspot.com to see what they've created for folks like you.

The site appears to have been steadily improving over time.

I'll bet this has been going on without your being aware of it.

The web site says they've been in business since 1999. That's the timeframe when NewMars.com was in it's early stages.

I scanned back a way in the updates log, to get a feel for the changes they've been making since they started out with a focus on Apple.

A key problem that I think persists, is the inability of you (as a member) to give customers/readers a URL that points directly to an article you want folks to see.

Instead, you have to suggest a convoluted search process that only the most diligent and persistent will put up with.

I wonder if blogspot.com has quietly implemented a way for you to provide direct URL pointers to your work?

My guess is you may have a way to contact the operators of blogspot.com.

I just made a bit of a discovery ... blogger.googleblog.com

The address above is what showed up whan I clicked on a link called "Blogger Buzz".

When I clicked on Help I find myself looking at support.google.com

I tried "talking" to the Help feature and it did not help much.

OK... the next thing is... how can NewMars.com/forums help you provide access to your publications?

You don't have a Wikipedia entry yet. I have an account and could learn how to create a top level entry, but I don't know how to do it at present, and in any case, there are folks who control what get's posted there, so negotiation would be necessary.

It would be possible for us to create a topic for your publications, and in that topic we could create an index.

The index would point to posts, and those would point to files and images as they do now.

(th)

kbd512 · 2025-01-03 14:26:09

GW,

I thought you were using 355s and 230 tons-force as the Isp and thrust for Raptor based upon the numbers shown in the spreadsheet screenshot. That's my fault. My eye was drawn to the top of the spreadsheet. Until I opened the image in a separate tab, I could not read it well enough. Again, my fault, not yours. I really need a new LCD screen for this laptop. Everywhere I should see "white", I also see a bunch of vertical pink / magenta lines running through it, because my laptop LCD screen is failing, which makes reading anything on a white background rather difficult. Any other color displays okay, no matter how light, but not pure white.

Your screenshot for Centaur-V performance merely shows "Axis Title" for the performance chart, on both axes. That definitely needs to be fixed.

Source for Centaur-V Empty Stage Mass:
https://space.skyrocket.de/doc_stage/centaur.htm

GW Johnson · 2025-01-04 09:45:52

Thanks Kbd512. I just fixed that fault.

GW

tahanson43206 · 2025-01-12 21:33:23

During the Google Meeting of 2025/01/12, GW Johnson showed us these images for the discussion on Space Tugs and the Counter Rotating vessel concept.

The design would fly flat on. In the atmosphere that would be a problem but in space there would be relatively little "air" resistance.

It should be possible to change the orientation of the vessel by slowing or accelerating the rotating habitats.

I sure would like to see a Real Universe animation of the operation of this vessel design.

GW explained that the axle for the habitats would run through the entire ship, and it would extend out at the ends for the Space Tug to apply force. I'm assuming GW has planned for distribution of force to all parts of the vessel, but in this conceptual diagram we do not see force vectors.

Counter Rotating Vessel plus Space Tug-assisted

Baton style artificial Gravity

Space Tug assisted Earth Departure

(th)

tahanson43206 · 2025-01-13 08:24:39

for GW Johnson re Terraformer's doubts about the negative effects of rotation on the human mind....

In a topic created by Terraformer you hinted at research on the effects of rotation on the human mind...

https://newmars.com/forums/viewtopic.ph … 59#p213559

Since Terraformer appears not to be convinced, please see if you can find links to the evidence you read that led you to your conclusion that 3 or 4 RPM is the maximum that humans can tolerate for extended periods.

The Coriolis effect would be pronounced at 3 or 4 RPM, and the difference in gravity between head and feet would be disconcerting.

To my knowledge no research has been done using facilities purpose built to test humans in a rotating environment for extended periods, but you may know of some.

(th)

GW Johnson · 2025-01-14 14:06:40

I don't know of any formal studies that were ever done. Maybe there were, maybe not. Most of the spin rate limit stuff is just anecdotal. Carnival rides often exceed 100 rpm, but are limited to about 2 minutes continuous exposure, and yet some riders throw up, especially if conditions vary.

As for the gravity gradient, consider 56 m spin radius at 4 rpm, with 1 gee at the rim, and zero gee at the center. Acceleration is proportional to radius, and to spin rate squared. The spin gravity gradient down the spin radius is 1 gee difference/56 m = 0.01786 gees/meter. For a human 1.7 m tall, standing up, the difference in gravity he feels at his head vs his feet is height*gradient = 0.030 gees difference. That would be very hard to discern with ordinary senses.

Now do this at a higher rpm with a shorter radius, say 14 m at 8 rpm, for the same 1 gee at the rim. Now the gradient is 0 to 1 gee in only 14 m, or 0.0714 gees/m. The same 1.7 m tall person, standing, would see a gee difference head-to-feet of 0.1214 gees, which might actually be discernible by human senses.

The higher the spin rate (assuming it is even tolerable long-term), the bigger the head-to-toe gee difference will be.

But the coriolis effect is quite discernible even at 4 rpm and 56 m radius, yes. It will be hard to play any sort of ball games. It's just worse at higher spin rate and lower radius.

GW

tahanson43206 · 2025-01-14 19:40:59

GW Johnson has been working on a paper for possible presentation...

The paper has progressed to the point it is ready for review by NewMars members, if anyone is interested...

Settlement pdf
https://www.dropbox.com/scl/fi/12vl87q0 … u1xx3&dl=0

Presentation slides in pdf form
https://www.dropbox.com/scl/fi/xs775irw … ng6f7&dl=0

Presentation Notes:
https://www.dropbox.com/scl/fi/ltmok0t0 … b72sw&dl=0

GW Johnson · 2025-01-15 10:05:21

The links work fine. The article is pretty close to its final form. The slides may need more edits, maybe not. Slides make more sense if you have the presentation notes handy.

GW

tahanson43206 · 2025-01-15 13:45:16

For GW Johnson! Thanks for testing the links to the three files offered in Post #494.

In this post, I would like to (at least try to) encourage you to test your unproven and completely hypothetical concept for a baton configuration for deep space missions.

A live test needs to be done with actual equipment in LEO. The idea that you can achieve stability and a livable environment for humans on board your proposed design is ambitious. I consider it to be ** extremely ** ambitious.

You need a very wealthy patron.

No government on Earth is going to fund the experiment.(*)

To find such a patron, we have a couple (maybe three) options...

1) Publication which has a chance of being seen by a wealthy person, or by a friend or employee
2) Internet broadcast of some kind ... YouTube video is an option you have already mastered
3) Correspondence or direct phone call

You've already created documents that show the concept.

You will need support by others to gain the solid knowledge that will convince funders to invest in your concept.

(*) governments will fall all over themselves to ** copy ** your idea, once it is shown to work.

(th)

GW Johnson · 2025-01-15 19:03:44

The fundamental feasibility of baton spin has been in evidence at Friday football games for many decades, much longer than there has been a space program of any kind anywhere. Baton twirlers sending their batons skyward proves it can work, because those spins are utterly stable. If that were not true, those girls would not reliably catch the spinning batons as they fall back.

As for the detailed stress analysis, that requires more sophistication than I have at my personal command, but there are few if any surprises waiting in the wings, very much UNLIKE cable-connected spin concepts. The spin of rigid bodies is quite well understood already by engineers. If it were not, then tire-balancing machines would not be possible. It is the cable-connected concepts that have all the unknowns.

Baton spin is by definition a rigid-body approach.

GW

Last edited by GW Johnson (2025-01-15 19:04:39)

tahanson43206 · 2025-01-15 19:49:08

For GW Johnson!

Your post #497 appears to be making a convincing argument.

However, please consider how well the baton would perform if it were filled just before the toss with bean bags of various sizes that move about during the spin.

I suspect you will find that the baton you're thinking about was made in a high precision manufacturing plant, and that it passed balance tests before it was released for sale.

I'm not arguing ** against ** the baton idea! I am arguing ** for ** ground tests of real articles filled with people, supplies, machines and fluids of various kinds.

In addition, the mathematical simulation programs available in 2025 should be sophisticated enough to provide useful feedback.

My guess is you will find that in service, the captain of one of these vessels will exert tight control over movement, just as would be the case in one of the rotating habitat ring designs.

(th)

tahanson43206 · 2025-01-18 21:28:21

GW Johnson has provided a spreadsheet with four sheets and a companion user's guide for those who might wish to study artificial gravity using rotation. The study looks at several scenarios in depth.

Here are the links:
Spreadsheet:
https://www.dropbox.com/scl/fi/pg3hm3bb … muok2&dl=0

User Manual:
https://www.dropbox.com/scl/fi/67pq30i3 … sl5dr&dl=0

User Manual update 2025/01/20: This update includes reference to the NASA funded study of rotation training as found by Terraformer:
https://www.dropbox.com/scl/fi/67pq30i3 … vhjx4&dl=0

I am hoping we can discuss this tool set during the upcoming Google Meeting on January 19th.

If our European members would like an earlier training session I would be willing to ask if we could create one.

Update: Opening paragraph in User Manual:

User Manual for “Spin Gravity Stuff.xlsx” Spreadsheet G. W. Johnson 1-15/18-2025
This is just a rough-estimating tool for sizing spin gravity designs in 3 size classes. Small designs
use baton spin mode, for a handful to maybe a dozen or so people. Medium size designs use
centrifuge wheel spin mode, with the spin axis along the vehicle body axis, but the wheel diameter
larger than the rest of the body diameter, for hundreds of people. Large designs are simply big long
cylindrical spaceships using rifle bullet spin mode, for thousands of people.
There are 3 worksheets in this spreadsheet file: “baton spin”, “centr whl”, and “rifle bullet”. The
“centr whl” refers to “centrifuge wheel”. There are other possibilities for somewhat intermediate
designs, such as the “frisbee” analog to the big, long rifle-bullet spinning cylinder, and 3-or-more
radial arms to a baton-spin design, instead of just the straight-through two. No worksheets for
such are currently included, although they could be added later.

(th)

GW Johnson · Today 09:04:26

I checked the links. They all work. Both links to the user manual lead to the same updated document. That update is a dated paragraph added to the spin rate discussion near the end. It refers to the recent NASA data.

I know Terraformer posted a link to the NASA document reporting their 2020-vintage gee-acclimatization studies, because I found it and scanned the document. But I have so far been unable to find that link again, to take a closer look.

GW

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