Google Meet Collaboration - Meetings Plus Followup Discussion

GW Johnson · 2025-04-05 17:04:25

I do not know what that heating system might really look like. I have yet to even bound the heat transfer problem, which will be the "long pole in the tent".

You have to understand, heat transfer, especially via gaseous media, is about the slowest physical process that we know. The proof of that thesis is the vast difference in time it takes 32 F air to kill you, versus 32 F water. And that transfer process is termed "convection", not "conduction". Conduction occurs within solid media that are in intimate contact.

GW

kbd512 · 2025-04-05 18:06:06

GW,

My opinion is that we will use induced turbulent flow to do a better job of transferring the heat into the Hydrogen. Maybe we don't even need a porous graphite core as such, for a flow rate of only 1 to 2kg/s, and a hollow channel wall cylinder design will work better. If we need more channel wall surface area for super heating or extended residence time in the engine, then we can use our large 100:1 expansion ratio nozzle as part of our heat exchange surface area. This will keep the engine as light as possible.

I won't pretend to know what the optimal approach is, so I'm not ruling out any particular approach unless it results in impractical component sizes, performance requirements, or costs. The major parts of the propulsion system have to be transportable to orbit in a Starship, or they're not very practical. As far as materials are concerned, we have the materials of the NERVA Program (Graphite structure with Zirconium Carbide cladding) which are known to work, as well as newer materials (Hafnium Carbide cladding) known to work even better.

tahanson43206 · 2025-04-06 07:44:57

The weekly Google Meeting is on track.

If all goes well, the waiting room will open at midnight UTC - 8 PM New Hampshire - 7 PM Houston

GW Johnson will be away on this occasion.

The waiting room is open at 23:58:23 UTC

https://www.reddit.com/r/rocketry/comme … ?rdt=38794

https://beyondnerva.wordpress.com/nucle … derations/

https://www.intechopen.com/chapters/81555

https://kb.osu.edu/server/api/core/bits … 9a/content

Post meeting report:

This was a ** really ** productive meeting! At this point, we appear to have the optical collection system stable, and the nozzle assembly appears to be approaching stable. The heating chamber is now receiving all the attention.

The links shown above in this post were provided by kbd512 as we proceeded. We also called up documents provided earlier by GW Johnson.

A key finding from the meeting is that the NERVA rocket used some method (we do not yet understand) to provide a long dwell time for hydrogen traveling through the body of the reactor that allowed the hydrogen to absorb the thermal energy that was present when the hydrogen passed through the throat and out into the expansion bell.

The External Heating chamber is going to have to perform a similar slowing function. At this point we don't understand how best to do that, but the team members are fully engaged, and we may have an answer next week.

(th)

kbd512 · 2025-04-06 20:12:24

tahanson43206,

Thermal Hydraulics Design and Analysis Methodology for a Solid-Core Nuclear Thermal Rocket Engine Thrust Chamber

Edits:

Affordable Development and Demonstration of a Small Nuclear Thermal Rocket (NTR) Engine and Stage: How Small is Big Enough?

Non-Uniform Heating Impact on Specific Impulse in Nuclear Thermal Propulsion Engines

Nuclear Reactors - Spacecraft Propulsion, Research Reactors, and Reactor Analysis Topics

Mechanical properties of molded graphite-modulus and strength

Scientists successful in 3D printing complex graphite parts with 97% purity

In our meeting, I asked about the idea that a very large / high expansion ratio "channel wall nozzle", 3D printed in Carbon / Graphite, with an enormous amount of internal surface area and volume for heating of the Hydrogen propellant, could provide sufficient residence time to allow the Hydrogen propellant to achieve 3,000K:
index.php?action=dlattach;topic=34421.0;attach=1692149;image

An incredible variety of internal heat transfer tube configurations are possible, if they prove beneficial:

NERVA Fuel Element Diagram:

Proposed NVTR Fuel Element Diagram:

Last edited by kbd512 (2025-04-06 21:29:56)

tahanson43206 · 2025-04-13 06:13:00

today is Google Meeting day for NewMars forums!

If all goes well, the waiting room will open a few minutes before midnight UTC, 7 PM Houston and 8 PM New Hampshire.

The main topics I know of include:

1) Optical Plane vessel
2) GW Johnson's study for RGClark's question about large heat shields

Other topics may be and likely will be introduced by attendees

Post meeting report:

That was fun! SpaceNut joined us for the first half of the meeting, and GW Johnson came in for the second half.

SpaceNut is making progress in remodeling his home there in New Hampshire, but there is a lot more to be done. A detail is that the local building code requires 8 inch by 8 inch beams for a part of the house that is being extended. The existing 2x4 joists will be allowed to remain in place.

SpaceNut is going with a metal roof but is waiting for the contractor to finish another job.

For kbd512: If you can please update the registration message to include the email address.

The message currently reads:
This forum is accepting new registrations via email. Please see Recruiting Topic

Please change it to:
This forum is accepting new registrations via email. Please see Recruiting Topic for additional information. Write newmarsmember@gmail.com

That is not too much more than we have now, but hopefully it will help anyone who might be interested in applying for membership.

For GW Johnson: That "segment" you asked about is the height of a row of the optical devices.

Each optical device can collect one watt, and each device is 36 mm in diameter. We are allowing 2 mm for spacing.

The URL for the program you saw is: http://40.75.112.55/Optical/heat_pipe_study_08.html

(th)

tahanson43206 · 2025-04-20 06:06:06

Today is a special day for many on Earth, so family duties may take precedence for NewMars members who might attend the weekly Google Meeting. However, I'm planning to open the Waiting Room at midnight UTC as usual. I've been working with ChatGPT4o to attempt to build a model of the engine for the Optical Plane space vessel. We've run into some snags, so the model may not be functional. I'll be ready to show what we have, and to answer questions (as best I can) about the process.

We usually have other topics that come up for discussion.

Midnight UTC is also 7 PM Houston and 8 PM New Hampshire.

Last week SpaceNut joined briefly to report on his progress with a major home renovation.

(th)

tahanson43206 · 2025-04-20 14:24:53

ChatGPT4o and I made a valiant effort to try to bring a Merlin engine tutorial forward from several years ago to the present state of development of OpenFOAM CFG (computational fluid dynamics) software. The earlier version used a solver called sonicFoam, and what I have today is called rhoCentralFoam.

There is some pesky detail that prevents rhoCentralFoam from solving the problem and generating data. ChatGPT4o did confirm that the problem is caused by trying to take the square root of a negative number, which engineers actually do using the imaginary number (i), but apparently OpenFOAM is unable to deal with imaginary numbers. That said, we ** did ** get the tutorial running to the extent we can see the outline of the Merlin engine and we can see traces of flow of gasses moving through the outline of the object. Or it could be my imagination.

In any case, I expect to have the Waiting room open a bit before midnight UTC.

(th)

tahanson43206 · 2025-04-20 19:08:16

Post meeting report:

That was fun!

kbd512 and SpaceNut were present for a series of animated discussions about a variety of topics.

We've all got things to work on for next week.

Meanwhile, for those who may be noting that GW Johnson was away, he has been engaged on a consulting gig.

In the midst of that, he took time to prepare another set of images about how to calculate orbits, which I posted in the Orbital Mechanics topic.

If we have a reader who would like to learn how to create drawings similar to the ones posted, the Traditional Orbit Course contains all the spreadsheets, text and pictures that a person would need.

It would be helpful if we (NewMars members) could somehow get the word out about the education offerings available on this site.

For those who might be interested, here is a set of links I used to put on a little "slide show" this evening:

Slide show ready:

On browser in tabs:

Tab1 – Optical device TIR
https://newmars.com/forums/viewtopic.ph … 70#p228570

Tab2 - 1950-s design for solar powered vessel
https://newmars.com/forums/viewtopic.ph … 60#p230460

Tab3 - Outline of Optical Plane Space Vessel
https://newmars.com/forums/viewtopic.ph … 94#p230594

Tab4 – art work Manta Ray
https://newmars.com/forums/viewtopic.ph … 89#p230389

Tab5 This URL points to specifications for the Optical Plane vessel
https://newmars.com/forums/viewtopic.ph … 93#p230393

OpenFoam ParaView

I was able to show the Merlin Engine OpenFoam model as a static image. It was possible to clearly see the outline of the engine.

I was NOT able to get the simulation running in time for this week's meeting, but will try again for next week.

I'll try to create a still image and post it here: This image shows a still of the Merlin model with temperature selected (blue = cold) and outline format

(th)

tahanson43206 · 2025-04-27 07:10:55

Waiting room is open at 23:53

Equipment check went smoothly at 23:21 UTC

***

Today is Google Meeting day on NewMars.

Things are looking favorable for a meeting at the usual time:
Midnight UTC, 7 PM Houston and 8 PM New Hampshire.

Depending upon attendance, topics may include discussion of RGClark's gigantic heat shield idea.
We will have updates on developments with the Merlin Engine simulation.

GW Johnson has multiple irons in the fire, so we might get a chance to try to catch up with some of them.

Post meeting notes:

Thanks to kbd512 and GW Johnson for another interesting and productive meeting!

We started out talking about the challenges of designing a heat pipe that will be capable of handling the severe conditions this project would entail.

We then spent some time considering the contract bid that GW is helping with ... this would involve ramjet technology with a solid motor.

Then we spent some time on the heat shield that RGClark introduced for discussion. I tossed the very large shield concept into the mix. It didn't win much support, but the discussion was interesting.

The final part of the meeting was spent in review of the OpenFOAM model of the Merlin Engine that we inherited from a defunct web site. The software that the model was built for no longer exists, because OpenFOAM has been evolving rapidly. The current model is set to the correct parameters but it crashes early, so there is obviously work ahead to try to find the right runtime settings. We reviewed the parameters that are in place, so at least everyone is aware of the initial conditions that govern the simulation.

To quickly review:
1) The pressure of the environment is set to 1 Pascal (open space or per GW, about 100,000 feet on earth)
2) The temperature of the environment is set to 4 Kelvin (open space)
3) The pressure at the intake is given as 5 bar (midway between GW's suggested range of 3 to 7 bar)
4) The velocity of hydrogen at the intake is given as 800 meters per second, assuming a flow of 1 kg/s which was set by kbd512 back in the beginning.
5) The temperature of that hydrogen is given as 3000 K, assuming it is output from a heat pipe.

With those starting settings, the simulation is able to compute all the way through time step 281, but 495 is the end of the expansion bell, so we have a way to go.

For RGClark from kbd512:

8:27PM
The heat shield tech NASA is working on for Mars aerobraking is called ADEPT, and it's a deployable NEXTEL-based fabric heat shield.

(th)

tahanson43206 · 2025-05-04 08:46:18

Today is Google Meeting day for NewMars.

The Waiting Room is due to open a few minutes before midnight UTC, 7 PM Houston, 8 PM New Hampshire

GW Johnson has published several new or updated studies.

SLS appears to be disfavored in the budget request.

New Mars Forums

Announcement

#276 2025-04-05 17:04:25

Re: Google Meet Collaboration - Meetings Plus Followup Discussion

#277 2025-04-05 18:06:06

Re: Google Meet Collaboration - Meetings Plus Followup Discussion

#278 2025-04-06 07:44:57

Re: Google Meet Collaboration - Meetings Plus Followup Discussion

#279 2025-04-06 20:12:24

Re: Google Meet Collaboration - Meetings Plus Followup Discussion

#280 2025-04-13 06:13:00

Re: Google Meet Collaboration - Meetings Plus Followup Discussion

#281 2025-04-20 06:06:06

Re: Google Meet Collaboration - Meetings Plus Followup Discussion

#282 2025-04-20 14:24:53

Re: Google Meet Collaboration - Meetings Plus Followup Discussion

#283 2025-04-20 19:08:16

Re: Google Meet Collaboration - Meetings Plus Followup Discussion

#284 2025-04-27 07:10:55

Re: Google Meet Collaboration - Meetings Plus Followup Discussion

#285 2025-05-04 08:46:18

Re: Google Meet Collaboration - Meetings Plus Followup Discussion

Board footer