AHC: build Rombus and Sea Dragon to launch a nuclear pulse Orion

Archibald

Banned
So why build both the chemical rockets? Pick which is best for the job at hand and just build that. Why both?
 
At work.

I think the point of the OP is to use the RHOMBUS/Seadragonas a 'First stage' to lift the Orion out of atmo before the atomic fire-works kick off.


I think the OP is asking advice as to which chem rocket type might be a better lifter?
 

Archibald

Banned
Nope, I want both in service - they are equally good. I would say Rombus is to ferrypeople - crew and passengers - aboard Orion, while Sea Dragon lift pieces of Orion probably assembled in orbit thereafter. As an alternative, Sea Dragon first stage may lift Orion to altitude before the atomic pulse engine starts.
 
At work.

Ah *Nods*

Well... from memory of the TED talks given by Dyson's Son then the 'Smaller' Orion put forwards I the Nixon era was to be lofted in two parts atop slightly tweaked Saturn stages.

So... with a Seadragon first stage... you're getting a LOT bigger tonnage lofted down range.

*Ponders*

So.. perhaps the Orion (Of what ever size) is lofted 'Empty' for safety/publicity reasons and then the RHOMBUS does ferry flights of personnel and material/fitting out?

Just some thoughts.
 
of course, the biggest advantage of Orion was that it could lift off from the earth's surface. Which you're totally negating by starting it in orbit.

Moreover, for the Saturn launched baby one of OTL
http://www.islandone.org/Propulsion/ProjectOrion.html said:
the core of the vehicle was a 200,000-pound "propulsion module" with a pusher-plate diameter of 33 feet, limited by the diameter of the Saturn. This design limitation also restricted Isp to from 1800 to 2500 seconds (39).
This beats the heck out of chemical propulsion, no doubt, but it's at the low end of Ion engine ISPs. (Although the thrust is obviously MUCH higher.)

And, you'd have to have a very stable world for other nations to be comfortable with the US continually setting off nuclear explosions in earth orbit.

Not to mention things like EMP effects on earth, effects on the Van Allen belt, etc.
 
Not to mention things like EMP effects on earth, effects on the Van Allen belt, etc.

I can't say for sure, but I suspect the EMP and Van Allen effects can be handled. The pulse propulsion units will be three to five orders of magnitude smaller than STARFISH PRIME, and you just need to be a little bit careful until you're out of LEO.

It's all the other problems that make Orion so unworkable in the absence of a convenient alien invasion.
 
Nope, I want both in service - they are equally good. I would say Rombus is to ferrypeople - crew and passengers - aboard Orion, while Sea Dragon lift pieces of Orion probably assembled in orbit thereafter. As an alternative, Sea Dragon first stage may lift Orion to altitude before the atomic pulse engine starts.
I think the problem is that they are both "equally good": they both have a payload of about 500 metric tons, they both offer large diameters for fairings, and they're both going to be massive investments in operations and construction--which because of their different operations is investment which is entirely duplicated by operating both. The natural tendency would be to operate one or the other, not both, considering how much they overlap.

On a rough first pass, I'd lean in favor of ROMBUS: some quick estimates of my own seem to point towards it being about 80%* cheaper than Sea Dragon using similar assumptions for expendable hardware production (for the tanks), and being able to assembly-line the smaller expendable LH2 tanks and reuse the pipeline of main ROMBUS vehicles is a much better operational model in my mind.

*Math error corrected here. I was using ROMBUS' tank gross mass instead of empty mass for the cost calculation. It's actually closer to 80% less expensive than Sea Dragon per first-pass math, not the 40% I originally had. With that in mind, there's no doubt in my mind that ROMBUS would be the best sole choice of the two
 
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Like to have a fleet of the Chrysler SERV to do the assembly in orbit, even though its many more trips.

ChryslerSERV_1.jpg
 

Archibald

Banned
of course, the biggest advantage of Orion was that it could lift off from the earth's surface. Which you're totally negating by starting it in orbit.

Good point. So let's invite to the party the fourth horseman of the space-pocalypse: Aerojet monster solid-fuel booster, the 260-inch thing, most powerful rocket ever fired.
http://www.astronautix.com/a/aj-260.html
2670 tons of thrust. A pair of those behemoth should be able to lift Orion into suborbital flight, before the nuclear pulse drive gets started..
 
Assembly in orbit is inefficient compared to just launching the Orion on a suborbital trajectory and lighting it once you reach a suitably high altitude. That way, your first stage can be optimized to just go straight up and down, and all your horizontal velocity can be imparted by the more efficient Orion drive.

Come to think of it, the 'Medusa' variant of the design is supposed to be more mass-efficient, substituting cables for shock absorbers. Maybe you could unfurl that while ascending and then light the drive.

I can't imagine any variant of the system flying without a very different Eisenhower Administration, one that is actually in favor of basing nuclear weapons in space. Then you might actually need a high-mass nuclear battleship to protect your assets and destroy the Soviet ones.
 

trurle

Banned
I would like to see Sea Dragon 1st stage + Orion combination. It balances nicely the level of nuclear fallout from Orion Engine and the excessive weight of the chemical rocket booster.
To make it really work, need a completely re-usable Sea Dragon 1st stage (if you do not want to discard a machine as large as naval heavy cruiser after each flight, which is not an option for any administration).

The real problem for Sea Dragon is the 360 MN (37 kt) thrust engine. Regenerative or radiative cooling of heavily-built combustion chamber is not going to work, especially if you imagine all protruding vanes necessary to eliminate combustion instabilities in huge chamber volume. It basically mean rhenium (with technology level of 1963) chamber and nozzle throat. Something like 200 tonnes of rhenium per vehicle, or 4-5 years of OTL world rhenium production per vehicle.

Therefore, building "Sea Dragon" would be an epic deed. Like "colony ship" in "civilization" or "c-evo" games (if you built it, you automatically assumed to be world ruler, new calendar starts from the day of the 1st flight "Space Era Year 1, Dragonember 1st"). And losing each Sea Dragon would be a major world disaster, enough to introduce a special national holiday along with Christmas. ("Dragon Mourning day, Orionember 26th").:p

More realistically about political climate..Sea Dragon requires united world. Without unification, any project of such complexity would be cancelled in favor of more bombers and ICBMs.

P.S. Rombus would have ~1/2 payload of Sea Dragon 1st stage for ~4 times lower launch mass - thanks to LOX/LH2 engines. Unfortunately, i cannot see realistically how the Rombus can be effectively reused. Dropping LH2 tanks and itself in 4 widely spaced lots is not simplifying re-assembly (see the sad economics lessons of Space Shuttle boosters re-use). Need to transport and re-mate huge blocks, instead of just refueling.

P.P.S. Integrating Sea Dragon with Orion would be also a huge challenge. Need to re-land Sea Dragon on launch site just on top of huge transporter (may be after refueling at touchdown site if different from launch site), vent residual propellants, use transporter to move Sea Dragon to maintenance hangar, mate Orion, load nuclear bombs, move assembled vehicle to launch pad, offload from transporter, connect the refueling pipes, load propellants, disconnect refueling pipes - and do not forget wrenches in the main gimbal!
 
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trurle

Banned
On Rombus
Douglas proposed them as Lofter for Orion puls engine
here there early concept with SSTO also launcher for Orion Nuclear pulse ship

source the unwanted blog
The picture does not make any sense together with comments. The picture shows a chemical TSTO (not SSTO) with payload looks like small parts of Orion engine.
 
The picture does not make any sense together with comments. The picture shows a chemical TSTO (not SSTO) with payload looks like small parts of Orion engine.

According my source
the "first stage" bring entire second stage and "Mars Mission stage" into orbit (payload 3,100,000 Lbs or 1406 metric tons !)
there the small Orion puls engine (102 ft or 31 meter ø) bring "Mars Mission stage" to mars

Alternative concept was that first stage catapult the Orion puls engine to 80 km hight and from to there nuclear detonation to escape velocity
 

trurle

Banned
According my source
the "first stage" bring entire second stage and "Mars Mission stage" into orbit (payload 3,100,000 Lbs or 1406 metric tons !)
there the small Orion puls engine (102 ft or 31 meter ø) bring "Mars Mission stage" to mars

Alternative concept was that first stage catapult the Orion puls engine to 80 km hight and from to there nuclear detonation to escape velocity
Ah, seems i understood. Ascend to 80km, decouple 1st stage, drop fairing, rotate the rest 180 degrees, and engage the Orion. Use chemical engines on these narrow and long fuel tanks later (may be for Mars landing or return for earth?)

Overall, seems to be very complicated, not very fuel-efficient (because of small Orion pusher plate) and definitely expendable design. No wonder it was cancelled so rapidly.
 
The real problem for Sea Dragon is the 360 MN (37 kt) thrust engine. Regenerative or radiative cooling of heavily-built combustion chamber is not going to work, especially if you imagine all protruding vanes necessary to eliminate combustion instabilities in huge chamber volume. It basically mean rhenium (with technology level of 1963) chamber and nozzle throat. Something like 200 tonnes of rhenium per vehicle, or 4-5 years of OTL world rhenium production per vehicle.

Really? Do you have the numbers for that? I thought the size of the nozzle meant most of the heat was kept away from the walls, meaning that the walls could cool themselves by being its own heat sink...

Combustion stability is something I've always wondered about with the SeaDragon. The size of the chamber seems like it would be a place you'd see all sorts of exciting new high-temperature gas phenomena.

I'mv daydreaming about these three awesome space vehicles. They happened more or less at the same time (before 1963 for Orion, 1962 for Sea Dragon and 1964 for ROMBUS)

The thing is, not only are SeaDragon and ROMBUS competing for the same niche, as well as being radically different approaches to solving the same problem. Building one doesn't give you experience that is particularly helpful for building the other. I think this means that while one or the other are within the realm of possibility, both happening in the same TL is near impossible (and if they were both built, I bet competition for the limited market of super-heavy launches would mean each would be made an economic failure by the other).

fasquardon
 

trurle

Banned
Really? Do you have the numbers for that? I thought the size of the nozzle meant most of the heat was kept away from the walls, meaning that the walls could cool themselves by being its own heat sink...
Exactly opposite. Cooling problem in large nozzles results from 2 scale effects:
1) Increased thermal flow resistance of thick wall even at the same conductive+radiative heat flux on inside surface
2) Decreased transparency of flame in large chamber, resulting in increasing radiative heat flux.

For small engines, one can use aluminum combustion chamber+nozzle with oxide coating. Larger chambers tended to use molybdenum steel with sulphide coating. And largest engines (from ~100 tons thrust) of 195x-196x were invariably constructed of rhenium. I remember several such material descriptions in contemporary AIAA journals. Later thermal coatings technology improved, and steel+sulphide range expanded to all production engines. Improvements come around the Space Shuttle program start time.
 
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