[ExI] fun memories of rocket stuff from a long time ago

[spike at rainier66.com]

-----Original Message-----
From: extropy-chat <extropy-chat-bounces at lists.extropy.org> On Behalf Of Adrian Tymes via extropy-chat
Sent: Tuesday, 30 September, 2025 9:25 AM
To: ExI chat list <extropy-chat at lists.extropy.org>
Cc: Adrian Tymes <atymes at gmail.com>
Subject: Re: [ExI] fun memories of rocket stuff from a long time ago

On Sun, Sep 28, 2025 at 10:40 PM <spike at rainier66.com> wrote:
> -----Original Message-----
> From: extropy-chat <extropy-chat-bounces at lists.extropy.org> On Behalf 
> Of Adrian Tymes via extropy-chat On Sun, Sep 28, 2025 at 10:18 PM <spike at rainier66.com> wrote:
> > That spreadsheet works for nuclear rockets too.  If you have any motor data, I will see if I can find an old copy of that spreadsheet, or failing that I can put together a new one (I still remember how) or failing that we can use one of the many commercial products that do rocket calculations.
>
> If you want to put the nuclear rocket we're working on through your spreadsheet - I sent you a copy of the report, right?  If it's got the data you need, go ahead.
>
> If I didn't send it, remind me on Tuesday.  There may be something related happening then that'll make discussion easier.
>
> _______________________________________________
>
> Cool thx Adrian.  Let's let it cool until then: I have matters of importance going on Monday and Wednesday next week and I am getting ready for a short camping trip the week after that, so no hurries.  I think I have a copy of that software in my archives.

It's now Tuesday.  The last of the export control barriers has been resolved, so we have finally published our report:
http://cubecab.com/white_papers/A_Path_Toward_Nuclear_Thermal_Spaceplanes.pdf

This is not a final design by any means.  With the radiation shielding, the thrust-to-weight only comes to about 3; we'd like to get it to at least 3.5, preferably 4, for reasons noted in the Spaceplane section.  (I think I know how to do this, if we can get funding for further development.)  But is this enough data to model this version in your spreadsheet?

_______________________________________________


COOL!

Adrian, looks like you have done a lotta lotta work already.  I wasn't aware your concept was this far along.  This stage of development looks like something you could pitch to the generals and get funding from DARPA.

I do apologize, for I fear my fingers have written checks my fingers aren't ready to cash: I don't have the bandwidth to study this now, with medics tomorrow and Thursday, then a camping trip next week, and the overall drive of getting ready to take in an elderly father in law who might need our help soon.  But I might have some helpful suggestions.

There is commercial software my son was using that appears to be good enough for creating plausible ascent profiles.  Unless we have specific fuel use profiles, my spreadsheet won't really do much for us anyway: it is designed for chemical rockets and will only estimate drag better than the commercial products, but even then it isn't clear how far those have advanced since Robert Bradbury and I worked together more than a decade ago.  Also: your nuke rocket appears to be a partial (clarification pls?) air-breather (or potentially a partial air breather (this approach has enormous advantages for the early part of the flight (after you go supersonic you get a free pre-compression from the intake shock wave (Ok not free exactly (actually expensive free pre-compression from the intake shock wave (if you see drag as money (and that shock wave is draggy compared to alternatives))))) and oh dear the complication that introduces into an otherwise fairly simple drag calculation, mercy.  

I don't claim to understand the maddening subtleties of shock waves around an intake.  That discipline is like medicine: every time you think you have the answer and all your equations work, shock waves somehow find a way to evade understanding.  Notice Elon Musk is still burning up perfectly good re-entry bodies by estimating what shock waves will do, using the simplified equations in our college textbooks.

Regarding thrust to wt of 3: that in itself will not prevent you from achieving single-stage-to-orbit necessarily.  You will have greater gravity losses with the leisurely acceleration profile, but don't write off the idea based on that alone.

I might hafta stand down for now and let you younger fellers do what younger fellers do so very well, while I cheer you on (but do try to avoid visualizing me leaping and cavorting in a poodle skirt and pom poms (for that is so very undignified (even by MY very loose standards for human dignity (I am known to cavort at every opportunity.))))

Fun aside: if working with a competitor is not out of the question: SpaceX funds edgy research like this, and it has advantages over working with pokey old super-conservative DARPA and such.  Musk is the kind of guy who will just say OK, let's just build that and try it.  He won't study it to death the way the military likes to do.  He has the money to do stuff like that, and isn't accountable to anyone if using his own funds.

Best wishes Adrian!

spike