RGClark Postings

RGClark · 2025-05-16 10:20:02

tahanson43206 wrote:

For RGClark re adjustable nozzle concept...
Since your latest proposal is for an expendable SSTO, you wouldn't be concerned with re-use of the nozzle.
Perhaps a design that slides out segments along the nozzle as they are needed would help?
https://encrypted-tbn0.gstatic.com/shop … DFl5s73O1_
Update at 1936 New Hampshire time:
For RGClark: https://newmars.com/forums/viewtopic.ph … 48#p231548
GW Johnson sent this image about how to cool two phase rocket engines.
(th)

I like that idea. There are several methods of doing variable nozzles. For instance they have been used on jet engine afterburners for decades:

Bob Clark

Last edited by RGClark (2025-05-16 15:56:56)

tahanson43206 · 2025-05-16 12:03:41

For RBClark Re #26 ... thanks for that helpful GIF! Hopefully GW Johnson will find inspiration.

GW Johnson has attempted to respond to the variable geometry nozzle idea, but I suspect you have missed all that input.

Your idea in this post: https://newmars.com/forums/viewtopic.ph … 10#p231710

caught my eye ... I'd never thought about the question before. I'll start looking for answers. I suspect the forum software designers planned for your scenario, but I've never had a need for it. I do recall that on other forums, there can be email notification of replies. I don't think this forum has that feature. You probably haven't noticed, but our senior Administrator is taking some time off to remodel his house, so that source of knowledge is not currently available.

Just FYI ... the reason I set up this topic was so we could communicate with you without placing our IDs on top of your post. It is important for our members to be visible in the Active list as long as possible, so others can see their updates to various topics.

It is available to you if you want to communicate with the admins. You can also use Housekeeping.

Update: I have asked GW Johnson to develop his previously published scenario for his SSTO concept, which I am confident you have never seen. I would appreciate your participation in a serious (non-academic) effort to develop a one-person reusable transport to LEO. I believe there would be a market for such a vehicle, with governments and uber-wealthy individuals as the opening customers, and more later as the vehicles prove themselves. If properly designed, such vehicles could operate just like an airliner, with expense of fuel as the greater part of expenses, just as I suspect it is today for airliners.

We might be able to draw other NewMars members into a serious effort. I am NOT interested in more endless academic discussion. If this can be done, let's set out to make it happen.

(th)

tahanson43206 · 2025-06-24 14:35:09

For RGClark re SSTO Engine technology...

Recently kbd512 has been looking at an air breathing system for SSTO.

I am wondering if you might be willing to entertain the idea of using air breathing propulsion for the flight to the top of the atmosphere, followed by traditional rocket engine propulsion. The difficulty of designing for sea level would be eliminated, and the remaining question would be how to design the engine for the optimum performance at the altitude where it begins operation.

In order for you to catch up with kbd512 you might be able to find relevant posts by searching for posts by kbd512.

kbd512 posts in a number of topics, so searching by topic might not work. Or you could just write a note to kbd512 asking for links to relevant posts.

(th)

RGClark · 2025-06-24 18:25:34

tahanson43206 wrote:

For RGClark re SSTO Engine technology...
Recently kbd512 has been looking at an air breathing system for SSTO.
I am wondering if you might be willing to entertain the idea of using air breathing propulsion for the flight to the top of the atmosphere, followed by traditional rocket engine propulsion. The difficulty of designing for sea level would be eliminated, and the remaining question would be how to design the engine for the optimum performance at the altitude where it begins operation.
In order for you to catch up with kbd512 you might be able to find relevant posts by searching for posts by kbd512.
kbd512 posts in a number of topics, so searching by topic might not work. Or you could just write a note to kbd512 asking for links to relevant posts.
(th)

Yes. We know ramjet propulsion is doable as operational ramjets have been fielded since decades ago. What we haven’t been able to do is scramjets that can work for more than just a few seconds of positive net thrust. But ramjets can operate up to Mach 5+, over 1.600+ m/s. This can subtract off a significant amount of the delta-v needed for orbit. This can certainly work for TSTO where the first stage is airbreathing ramjet, and the upper stage being a rocket. This can cut the cost to space since the airbreathing first stage might be reusable for thousands or reuses.

It might also work for a airbreathing/rocket combined-cycle SSTO. I am investigating this possibility.

Bob Clark

tahanson43206 · 2025-06-30 08:22:32

For RGClark re kbd512's SSTO topic...

The three of you (kbd512, GW Johnson and RGClark) have combined to create a topic that in my judgement is worth the time of anyone who chances upon it.

I just reread the topic from the top, and while no one ever persuades anyone of anything, the exchanges are illuminating for non-participants.

I came away inspired to wonder what the performance of various fuels would be if they were able to lift themselves to orbit without the annoying encumbrance of inert mass. A table of performance for various fuels would show the capability of each fuel, and while actual SStO will probably never happen because of that annoying need for inert mass, it would be (or could be) inspiring to clever humans to ** try ** to find a collection of inert mass that could go along for the ride.

My guess is that it might not be too difficult for a talented person to put together a table showing performance of various fuels. The designer of such a tool would need a tonnage of propellant to work with, so I'll toss out 100 tons as a reasonable mass to consider. Such a table ** should ** result in numerous posts by NewMars members showing how advances in human knowledge might lead to actual success.

To make the exercise more interesting, I'd like to propose a Rule for the Game: Nothing is to be discarded on the flight.

The post productive flight would be one in which the non-fuel component is completely useful after it is delivered to orbit.

(th)

tahanson43206 · 2025-07-01 08:53:23

For RGClark ....

First, thank you for pursuing the current investigation of throat adjustment as an alternative to bell length adjustment.

Second, as you work with GW Johnson, please see if you can reveal where the throat adjustment component resides.

In a recent post you suggested injecting propellant as a way of ? somehow ? adjusting the throat? That is an interesting idea and I hope you will see where it leads.

GW Johnson has said repeatedly that if a rocket engineer installs a vacuum bell on a rocket that is used at sea level the forces generated will cut off the bell at whatever point the physics requires. He used the correct language of course. What I'm curious about is how changing the shape of the throat might reduce that problem?

I appreciate your persistence in the study of this set of problems.

(th)

tahanson43206 · 2025-07-02 06:19:50

For RGClark re Rocket Engine Design

GW Johnson has once again stated the principles of practical rocket engine design in the Rocket Engine Design topic:
https://newmars.com/forums/viewtopic.ph … 48#p232548

You have been offering questions that I am hoping will lead to learning opportunities for readers.

All rocket engine designs to date have been based upon the idea of a solid material strong enough to survive the challenging conditions of chemical combustion. The premise seems to be that a solid material will be able to hold it's shape (throat in particular) and various cooling techniques are used to prevent melting or erosion.

You have shown us various attempts to modify the expansion bell in the transition from sea level to vacuum.

Your inquiries provide an opportunity for members and readers to think about materials that might allow for the shape of the rocket to change as the amount of atmosphere back pressure decreases during flight.

It might be possible to design an engine that changes shape during flight, if a material that does not currently exist were discovered.

One glimmer of possibility arises from your inquiry about changing the shape of the throat, by introducing a needle downward into the flow, and GW Johnson then reported some experiments along those lines. It would be interesting to see more about those experiments.

(th)

tahanson43206 · 2025-07-02 06:31:48

For RGClark re question about injecting fluid into the throat to simulate restriction of the area of the throat...

https://newmars.com/forums/viewtopic.ph … 49#p232549

Thank you for this interesting question!

It appears to me that you and GW Johnson are not quite yet on the same page....

It seems to me that you are talking about the see level to vacuum rocket engine design problem, and GW is talking about ramjets.

Please continue trying to investigate your idea.

At the very least, we may end up with a better understanding of the physics of how your idea would play out.

As an observation... modern CFD systems may be able to stimulate the scenario you have described.

A package called OpenFOAM is available for you to run on your own computer. The system is free and reasonably well documented, and there is a new book about the system approaching publication. The publication date has been moved back from June to August.

It takes a fair amount of time to understand how to work with this powerful tool.

It may be possible to see the effects that GW Johnson has been describing in a simulation. The simulation can be captured in still images or even in a movie so they can be viewed by an audience.

(th)

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