General Dynamics Triamese (1968)

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Convair Triamese boosters via San Diego Air and Space Museum archives posted on Flickr.
 

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I checked, we don't have a dedicated thread for this one, only scattered bits here and there. Because it bursted that forum attachement limit, I posted it elsewhere.

Something that puzzled me reading that document, seems that the Triamese orbiter had a complete Gemini-B stuck in its nose for crew escape. Weird.
 
seems that the Triamese orbiter had a complete Gemini-B stuck in its nose for crew escape. Weird.

Errrmmm... not *exactly:* "A two-man escape capsule is provided in each element of the spacecraft based generally on the Gemini B re -entry vehicle. "

"Based on" covers a whole lot of ground. There might well have been little recognizable beyond, say, the rudiments of the pressure shell, maybe the ejector seats, some instrument layouts. If you look at the interior views on page 3-14, there is nothing to suggest Gemini *anything.* Heck the pilot and co-pilot are oriented parallel to each other, not angled as in Gemini B
 
Triamese reusable space transportation system has the attractive operational capability and significantly reduced operational cost, The concept has been named Triamese since it uses three virtually identical elements to deliver its payload to orbit, Each element is a rocket-powered, vertical takeoff, horizontal landing, reusable vehicle. Good subsonic performance, attained by variable geometry wings, coupled with the use of turbofan engines provides a cruising capability that enhances both operational and logistics activities. Two of the vehicle elements operate as boosters from liftoff to a staging velocity of about 8,000 - fps, after which they decelerate and fly subsonically to a suitable landing site. The orbital elements, complete with payload, then accelerate to low earth orbit. Prior to staging, the rocket engines of all three elements are operating with propellants from
the booster elements.

View: https://www.youtube.com/watch?v=DPPQ0ht0XCI
 
Ye olde Marcus Lindroos website, vintage 2001.

And the Triamese entry.

So now we have, in the same thread
- Triamese 1968 tech report
- Triamese early website, vintage 2001
- Triamese 2023: Hazegrayart CGI artwork

Because the Triamese was such a smart concept, on paper at least. Never would have thought, back in 2003, I would ever "see" the Triamese fly in such high-res, realistic CGI.
 
Ye olde Marcus Lindroos website, vintage 2001.

And the Triamese entry.

So now we have, in the same thread
- Triamese 1968 tech report
- Triamese early website, vintage 2001
- Triamese 2023: Hazegrayart CGI artwork

Because the Triamese was such a smart concept, on paper at least. Never would have thought, back in 2003, I would ever "see" the Triamese fly in such high-res, realistic CGI.

And now it DOES fly . . . Falcon Heavy . . . ;)

cheers,
Robin.
 
Ye olde Marcus Lindroos website, vintage 2001.

And the Triamese entry.

So now we have, in the same thread
- Triamese 1968 tech report
- Triamese early website, vintage 2001
- Triamese 2023: Hazegrayart CGI artwork

Because the Triamese was such a smart concept, on paper at least. Never would have thought, back in 2003, I would ever "see" the Triamese fly in such high-res, realistic CGI.

And now it DOES fly . . . Falcon Heavy . . . ;)

cheers,
Robin.
Delta IV Heavy flew earlier
 
I t did indeed, and I forgot about it . . .
But the point still stands, as Falcon Heavy is re-usable, as the Triamese was meant to be, whereas, the Delta IV Heavy was purely expendable.

cheers,
Robin.
 
Common cores that are actually interchangeable (unlike delta and Falcon), that can act as either S1 or S2, that can reenter and be recovered from both a hypersonic speed and from orbital reentry, and with a separate aeroshell? That sure does sound like an extremely inefficient engineering nightmare.

The idea of triamese-style launchers pops up occasionally, but I never got the point of it.
 
There is a major difference between Delta IV / F9 and Triamese, expendable or not. It is: the second stage. Triamese had three identical bodies but no stage 2. Delta IV & F9 have second stages, hence the "central stick" doesn't go into orbit. And yes, it makes a big difference. Falcon 9 central stick returns from 2 km/s or less, when Triamese center body would have had to return from 9 km/s. Not only much harder on the TPS.
The tradeoff is:
central stick going to orbit and back
versus:
central stick with a second stage on its shoulders.
And that second stage is expendable, because bringing back from orbit would be too hard.

Triamese made no compromise: central stick was going to orbit, rather than sending an expendable second stage to orbit.

Because it made no compromises however design of that central stick was kind of compromised.
It is pretty hard to be, altogether
a) identical to the side sticks
b) while going to orbit
c) then return from orbit.

Basically the above compromise was almost impossible, and this was the reason why NASA rejected Triamese out of Shuttle studies early 1969.

The only way to solve the "compromise" is to make the central stick different from the side sticks, but then it is no longer a Triamese ! That's the sheer absurdity that doomed the proposal.

Now @martinbayer, veteran from the FLPP / FESTIP studies, would tell you that going bimese rather than trimese, with the two vehicles slightly asymetrical, may work. Asymetrical bimese rather than symmetrical trimese: that's the way to go.

More on this later.
 
Bottom line: symmetrical bimese or trimese - MUSTARD, Triamese - only works in Hazegrayart stupendous CGI. In the real world, doesn't works very well.
What works is
- trimese with a second stage (Delta IV is an expendable variant, F9 is reusable, minus the second stage).
- "slightly asymetrical bimese" (per lack of a better name).
Another subtility is to keep the same outer mold line and change the interior elements: swaps internal tanks of LOX and LH2 (and RP-1 if tripropellant: use the wings, which is a very smart idea).

I have two example in mind: FESTIP FFSC-16 and Mel Bulman Variable Element Launcher. See the two papers.
 

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Fun fact: the ultimate "asymmetrical bimese" was... the original Space Shuttle: 1968-70. Same SSMEs for the booster and the orbiter, both fully reusable. Besides this however the two vehicles had little in common...

2sts_nar.gif
 
When you think about it, the "logical" progression should have been:
- Delta IV Heavy (triple sticks, expendable second stage, same propellants - but expendable with different engines)
- Falcon 9 Heavy (triple sticks, expendable second stage, same props - same engines, reusable sticks)
- Triamese / MUSTARD (triple sticks, fully reusable, no second stage)

But technical realities "derailed" that into
-asymmetrical bimese
- then the above shuttle (VERY asymmetrical bimese)

And finally - the 1971 Shuttle bastardized monstrosities that led to the actual vehicle.
 
What works is
- trimese with a second stage (Delta IV is an expendable variant, F9 is reusable, minus the second stage).
- "slightly asymetrical bimese" (per lack of a better name).
Even a slightly asymmetrical Bimese is inefficient, because you’re still having a S1:S2 mass ratio that is too close to 1.

A common core trimese with upper stage is better, but there is still the problem of different reentry speed and flight profiles for the central vs side cores, the difference probably is manageable when the Center core is only throttled down like FH, but it can be significant if propellant crossfeed is used like for the GD trimese, the boosters stage low while the core stages close to orbital speed...
 
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I t did indeed, and I forgot about it . . .
But the point still stands, as Falcon Heavy is re-usable, as the Triamese was meant to be, whereas, the Delta IV Heavy was purely expendable.

cheers,
Robin.
The second stage is still expendable and more often than not, the center core is expendable.
 
More Triamese. Google Books has a pretty good search function: a "date range" option. For example in that case I put 1966-1975 to track down whatever paper and publication mentionned "Triamese" in that time span.


It works pretty well in that case because "triamese" is no ordinary word.

There is some truly awesome stuff in the big NASA Hearings, which can be downloaded for free.

There are tons of stuff like that out there: Big Gemini, ILRV, Skylab B, canned Apollo missions... and it's the same for military aircraft and other vehicles. The Hearings are huge (up to 1300 pages !) and not easy to download and search - but they are like a big complement to the NTRS.
 
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I've just made one heck on a connection, related to the Triamese: Robert A. Lynch. https://airandspace.si.edu/support/wall-of-honor/robert-lynch
Same man worked on the Triamese flyback boosters in the 1960's (attached documents, confirming the Smithonian link above), and the BGM-109 Tomhawak in the next decade.
Now just think about it.
What's common to a) a Triamese flyback booster and b) a BGM-109 Tomahawk ?
- they have have fold out wings
- a cylindrical body
- they have to fly long distances without a pilot onboard
- on jet power
- they are to be produced in large numbers, to be cheap enough (for war or for access to space)

Just think about it: the Tomahawk as a subscale (and expendable !) Triamese flyback booster.
 

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Fly-backs and pressure-feds look to join the thylacene and the dodo
 
I meant Sea Dragon and the like---though Starship's strength is (partially) from pressure.
 
I stand corrected.
Falcon just gives off “falling locomotive” vibes more than shuttle did.
 
I stand corrected.
Falcon just gives off “falling locomotive” vibes more than shuttle did.
flying brickyard. Not much difference. Falcon does it more efficiently, with minimal external support and a smaller area.
 

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