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#1 2026-10-26 09:51:33
- offtherock
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- Registered: 2017-10-26
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New Rocket Design
Single Engine, Multiple Stages
I was thinking of a different rocket design.
If we could use the same engine, all the way from Earths surface to Low Earth Orbit.
As well as reaping the benefit of multiple stages.
That should increase payload to orbit significantly.
I was thinking, of having a rocket, made out of modules.
There are 3 types of modules.
Engine module
Cargo module
Fuel module
At the bottom sits the engine modules.
On top of it, is at least one cargo module.
Then there are the fuel modules.
When the engine ignites, the fuel. gets taken, from the topmost fuel compartment.
Then when that compartment is empty, the engine turns off
leading to a temporary upwards pull of the rocket.
We then let go of the top fuel module.
And it glides away and the moment the rocket has a clear road ahead,
the engine takes off again.
Continues this way until in space.
This way, we can use a single engine module, all the way to low earth orbit.
as well as having multiple stages.
When it comes to the landing there are multiple possibilities.
The modules would then be landing, one after another.
Multiple small landings, rather than one huge.
so the same landing infrastrucutre gets used more often.
as well as needing not be as large.
Would love to hear your thoughts.
i asked chatgpt.
https://chatgpt.com/share/6adf8639-b904 … 65aca717aa
Last edited by offtherock (2026-10-26 10:56:57)
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#2 2026-10-26 10:32:53
- tahanson43206
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Re: New Rocket Design
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#3 2026-10-26 11:12:08
- offtherock
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Re: New Rocket Design
also, using this method.
semi complete reusability could reached much more easily.
eg the last coupled of fuel modules, could just not be reused.
as they are falling from a high altitude at high velocity.
then we´d be loosing, fuel containers, not engines like the falcon.
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#4 2026-10-26 11:15:05
- Calliban
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Re: New Rocket Design
So basically, a rocket with drop-tanks instead of stages. This is basically how the shuttle worked. It isn't impossible, but there are few problems I can see:
1. The fuel and oxidant supply lines from each tank would need to be flanged in some way. Those flanges must reliably contain propellant under pressure during operation, seperate reliably and not spill propellant as they do. How to do this? How was it done for the shuttle?
2. Given that this was done on the shuttle, did it really save that much money having a seperate disposable tank, rather than a lower stage?
3. Your engine module must be sized to provide enough thrust for lift-off and then reduce thrust substantially as the rocket mass is reduced as propellant is used up and tanks drop away. Not a problem in itself, but it means lugging the same heavy engines needed for lift-off all the way to orbit. How much of a mass burden is this? The shuttle dealt with this (partially) by using solid boosters to augment thrust at lift off.
A fourth, less important consideration. Presumably, the empty tanks are not reusable (they weren't on the shuttle), as they have no independent propulsion for landing? This might not be economically unachievable. The lower stage tankage could be made from hot-rolled aluminium-magnesium alloy that isn't expensive. But it becomes something you are throwing away on each flight. So it would have to be cheap.
Such a design wouldn't necessarily need to dump all of its tankage. It could keep it's upper stage tanks within it's structure and dump the lower stage tanks. This would have higher structural mass than a two-stage vehicle. But does the design simplification warrant the cost of lost payload?
An orbiter that dumps most of it's tankage before re-entry, can be a lot more compact. That consequently makes the heat shield smaller and easier to build and maintain. Not an insignificant advantage, given how finicky heat shields are. Maybe we can attach a heat-shield as a whole module to such an orbiter and unbolt and replace it between flights?
Last edited by Calliban (2026-10-26 11:21:23)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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#5 2026-10-26 11:22:07
- offtherock
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Re: New Rocket Design
im thinking all methods, would assume the object landing would be.. just falling.
in a controlled fashion.
no landing legs
no landing burn
no lander rockets
like they say, the best part is no part
one possibility.
is to have an engine, take off.
let itself fall alongside the falling module
move underneath it.
grab it.
then land
and it could use just some kind of chopters.
like a giant drone.
be it structurally similiar to the module
it should have a similiar terminal velocity
A single drone could be just near non stop, up and down.
and everything just lands.. without... anything.
or it could be a bunch of drones.
holding.. a net.
and they fall alongside the module but just... lower
and they move underneath the module and let it sit into the net as they are both in freefall.
then they just... put the chopters on full and land it.
its basically a place where things are falling from the sky
and they just... land.. in a net.
the savings are large because the landing fuel and landing legs is the most expensive weight for it had to go the whole round trip up and down.
Last edited by offtherock (2026-10-26 13:58:35)
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#6 2026-10-26 11:28:37
- offtherock
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Re: New Rocket Design
1. Yes those are some issues. Im not familiar with their implementations.
2. The shuttle was prohibitively expensive. I dont know if those two are equatable.
3. Yes the same engines at liftoff as in orbit. Theres some penalty there.
Maybe they could accept some former of insane acceleration in the end.
And maybe throttle them down and/or not use all of them when approaching orbit.
Last edited by offtherock (2026-10-26 11:30:20)
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#7 2026-10-26 11:45:00
- HG Muller
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Re: New Rocket Design
There are several problems with this approach:
1) Optimum engine design depends on the ambient pressure the engine works in; if this is low or zero the nozzle can be a lot longer and wider, to make the exhaust expand further (during which it accelerates some more). But at high ambient pressure the extra nozzle area causes negative thrust. With one engine all the way you cannot optimize it for both situations.
2) Initially you need very large thrust, to beat gravity with a fully fueled rocket. But the Tsiolkovsky equation tells us that most of the rocket's mass needs to be propellant to reach orbital velocity. So near the end of the launch the rocket might be 30-100 times lighter. With the same thrust you would the have an acceleration larger than a bone-crushing 30-100g. To prevent that you would have to be able to throttle the engine over a very large range, to a few percent of its thrust at lift-off. It would be technically very challenging to design an engine that can do this.
3) Pure fuel tanks can have a very large full/empty mass ratio, so you don't save very much by discarding an empty one.
4) Just stopping the engine won't shake off the top part; you would have to apply some positive and sideway acceleration to the jettisoned tank, or negative acceleration to the remaining rocket.
5) It is hard to start an engine when in free fall, because the propellant then just floats around in the tank, and will not nicely drain into the fuel line to the engine. The Saturn 5 did have a special separation ring between its 1st and 2d stage, with 8 solid-state rockets strapped to it, to provide enough acceleration for long enough time to push the propellant towards the bottom of the tank during the start of its five J2 engines. This ring was then jettisoned after the 2nd stage had ignited.
The Atlas used the opposit strategy of what you propose: it jettisoned two of its engines to reduce mass and thrust when it arrived at large altitude, only leaving one engine optimized for low ambient pressure for the remaining part of the launch.
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#8 2026-10-26 11:54:17
- offtherock
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Re: New Rocket Design
1. Yes thats why i think of it as an engine module. with x many engines. of possibly different sorts.
2. Yes this is challenging. Dont really know if it works or how well.
3. Now im confused. isnt that the whole point of multiple stages in general. And the other methods even add the engine as well.
4. Yes im not sure what is the best way to get it off.
5. Yes this is beyond my knowledge.
Last edited by offtherock (2026-10-26 13:13:12)
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#9 2026-10-26 12:03:25
- offtherock
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Re: New Rocket Design
No the top fuel module would not fall up as the engines throttle down.
because the air friction is pushing it down... onto the rest of the rocket.
im not sure how its departure should be achieved.
maybe we could just send one of em, ufc fighters up there.
and he could grab the rocket like they grab each others back and then do this backflip thing.
Last edited by offtherock (2026-10-26 12:27:22)
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#10 2026-10-26 12:38:14
- offtherock
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Re: New Rocket Design
it needs to tip, on one side. so the air stops pushing it back on the rocket and starts pushing it off... the rocket.
then a slight push at the correct time so it wont hit the lower modules on the way off.
Last edited by offtherock (2026-10-26 13:11:38)
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#11 2026-10-26 14:04:43
- offtherock
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Re: New Rocket Design
or we can have tubes. and the modules, using their fins. navigate themselves to hit those tubes. then inside the tube, we could use magnetic levitation to slow them down. or air pressure.
everything just falls. thats the dream.
Last edited by offtherock (2026-10-26 14:12:26)
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#12 2026-10-26 14:37:59
- HG Muller
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Re: New Rocket Design
1. Yes thats why i think of it as an engine module. with x many engines. of possibly different sorts.
2. Yes this is challenging. Dont really know if it works or how well.
3. Now im confused. isnt that the whole point of multiple stages in general. And the other methods even add the engine as well.
4. Yes im not sure what is the best way to get it off.
5. Yes this is beyond my knowledge.
1. With multiple engines you can easily throttle by switching some of them off. And if they are not of equal thrust you can switch the most powerful of, to reduce the thrust a lot. But... You would be taking a lot of engines with you to orbit that you really did not need anymore. That is a lot of dead weight.
3. Conventional staging also gets rid of engines that are no longer necessary, which reduces weight a lot more than just getting rid of the tanks. Like I mentioned, the Atlas only jettisoned engines, so apparently this is already worthwile in itself. Remember an engine is a lot more than just the nozzle.
It also allows you to change engines, to a type that is better optimized for the environment in which it is intended to operate. Higher stages need far lower thrust, and making them use an unnecessarily big engine that is heavily throttled is also dead weight.
There are intermediate forms. The Soyuz/Sputnik launcher basically uses its second-stage engine already at take off. But it jettisons 4 of its engines when their thrust is no longer needed, together with the fuel tanks they exhausted.
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#13 2026-10-26 16:07:03
- offtherock
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Re: New Rocket Design
1. Yeah that might be a killer.
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#14 2026-10-26 18:10:55
- kbd512
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Re: New Rocket Design
offtherock,
This is what your described rocket design reminded me of:
OTRAG - Orbital Transport- und Raketen-Aktiengesellschaft
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#15 2026-10-26 18:37:38
- kbd512
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Re: New Rocket Design
By using CFRP to design reasonably small booster stages with minimal hoop stress and keeping diameters sane, you could use a tape-winding machine to rapidly fabricate a low-cost tankage solution. 3D printing lets you integrate many engine features into a single part, with fewer joints and moving parts.
I could envision a 310-315s sea level Isp with computer-optimized injector design with exceptionally precise mixture control, which is what allows Relativity Space to create that beautiful blue-orange flame instead of the smoky soot-filled exhaust of lesser LOX/RP1 engines. OTRAG used hypergolic ignition, but I don't think that actually reduces the cost of a modern rocket all that much.
Anyway, to contain costs OTRAG used a low-cost stainless steel. If we stick with steel over CFRP, then I would say the new weldable Mangalloys (Hadfield steels) are much lower-cost than stainless, considerably higher yield strength so they can be thinner, retain excellent ductility at cryogenic temperatures, and are weldable. The Koreans and Japanese use austenitic Mangalloy (very high-Manganese steel) for cargo ships carrying cryogenic liquid methane, but it's been tested with LOX and LH2 as well. Presumably, the steel could be recovered and remelted, but not reused.
You're obviously going to get a much better propellant mass fraction with CFRP than steel, but steel provides a compelling cost advantage for routine delivery of 1-10t payloads.
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#16 2026-10-26 19:33:03
- kbd512
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Re: New Rocket Design
offtherock,
The original OTRAG rocket "cartridge" weighed ~330lbs, so Mangalloy steel would knock that back to ~187lbs since the austenitic grades of Mangalloy (60-65ksi) have approximately 2X the yield strength of austenitic stainless (28-32ksi). Wet mass was 3,300lbs, so the upgraded cryogenic-capable Mangalloy results in a dry stage mass per cartridge of only 5.66%. That's pretty darn good by any metric. Yes, CFRP would be lighter still, but CFRP is also expensive, and the tape-winding machines cost millions, whereas a thin sheet of electric resistance welded (ERW) Mangalloy would be dramatically cheaper and faster to produce.
Premium domestic-melt Mangalloy runs about $1-1.25/lb, so $187,000 to $233,750 for the raw materials to fabricate the 1,000X propellant tanks for a 5,000-10,000kg payload, which would be simple rolls of Mangalloy sheet steel. Staging sequencing matters greatly to the vehicle's payload performance. Foreign steels are modestly cheaper, but this is an aerospace vehicle that requires certified materials for the DoD or NASA to consider purchasing launches.
The engines probably need to be fabricated from some kind of stainless steel, but perhaps a single steel with appropriate aerospace coatings would suffice. You won't get away with using Mangalloy near hot O2, but again, aerospace coatings are your friend. A sodium silicate-bonded alumina coating would insulate and protect the propellant tank shells from corrosion. You can apply this coating to the engines as well, which is why I said you MIGHT be able to source a single non-stainless steel to fabricate the entire vehicle, though small components like igniters, control electronics, and whatnot still require other materials. However, 316L powdered metal for the engines is almost certainly cheaper than printing with Mangalloy, because you'd run into various power-related issues during printing that 316L doesn't have. You could mix some Aluminum into the Mangalloy powder to make it easier to print, but you still couldn't print Mangalloy the way you can with 316L, so you'd still pay a premium for the engine. 316L lets you use the laser at full power and fully solidify each printed layer in a single pass.
Edit:
The OTRAG engine weighed 44lbs, so 330-44=286, and half of 286lbs is 143lbs, so 187lbs in total, and IF the rocket propellant tank structure and engine structure can be made almost exclusively from Mangalloy, then the $187K to $233.75K raw materials cost figure provided is accurate. However, powdered metal is more expensive than sheet steel, so expect actual raw materials costs for 1,000X of these rocket cartridges to be higher because at least 44lbs is powdered metal. As previously stated, 44lbs of the total materials weight per cartridge probably needs to be stainless steel. A 45lb pail of 316L from Metal Powders USA is $1,057.50. That means the 3D-printed 316L stainless engine adds $1,057,500 to the cost of 1,000X cartridges. If transport/fab machinery/energy/labor roughly doubles the raw-material cost, then $2.5M for a 10,000kg payload is a pretty safe bet. That means the vehicle, less propellant, launch infrastructure, and operating overhead, is $250/kg to orbit. All that "other provisioning" might add another $200/kg, because it involves a lot of overhead.
Last edited by kbd512 (2026-10-26 19:46:13)
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#17 2026-10-26 20:26:24
- kbd512
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Re: New Rocket Design
offtherock,
As I wrote my edit to that last post, I thought about why engineers don't do this. You might save $50 to $75 per pound over existing methods, but there's a practical operational reality no amount of engineering can realistically overcome. Any rocket that operates on the OTRAG principle, which includes your proposal, would result in a stream of supersonic projectiles raining down over existing flight corridors unless you launch from very remote locations. This is the real non-starter and operational reality that the FAA and similar launch-authorization bodies wouldn't readily accept, because wind shear could blow empty propellant tanks over a progressively larger landing ellipse as the vehicle sequentially punches off empty propellant tanks or rocket cartridges on its way to orbit. There's also a danger to surface vessels. The sheer number of tanks/cartridges needed to deliver a 5-10t payload would quickly lead to a "hit" on a wayward airliner or fishing boat, based on basic probability metrics.
It's still an interesting concept, but it was ultimately dropped for political vs technical reasons. During the Cold War, France and the Soviet Union didn't want West Germany to have orbital launch capability because it would give them a de facto ICBM capability. The Soviets were understandably concerned, since the nazis developed the V2 during WWII and West Germany had nuclear reactors that could be used to produce Plutonium. I think Kahl opened in 1960 or 1961. I don't think they ever bred any Pu239, but I don't know for sure. I know that they built a fast breeder reactor intended to use Pu239 as fuel in the 1980s, but their anti-nuclear wackaloons shut it down. They also had a Pu239 separation facility at Wackersdorf to feed seed fuel to the reactor, but again, their environment-hating nutwhacks killed it.
Anyway, OTRAG and fast breeders were both part of a history that never happened because people hate themselves and each other far more than they love actual growth and potentially better futures with orbital rockets and true energy security. Sometimes one can only marvel at the fear/hatred/stupidity of it all.
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#18 2026-10-27 06:36:19
- HG Muller
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Re: New Rocket Design
one possibility.
is to have an engine, take off.
let itself fall alongside the falling module
move underneath it.
grab it.
then land
This is an interesting idea for realizing reusability. It applies the general principle for beating the rocket equation: don't take the equipment you need for safe landing (be it parachutes or retro-rocket propellant) with you to a high velocity that you will later undo. You leave that equipment at low velocity close to the surface.
There are some difficulties, though:
1) Higher stages might only jettison at such high speed (that is only safe at almost no air pressure) might not survive return to the lower atmosphere without a heat shield. In conventional rockets such stages often simply burn up.
2) It might be difficult to know in advance where exactly the returning stage will be close enough to the surface for the recovery craft to attach to it; if the stage is falling unhindered, the time window for picking it up will be small, so you must be really close.
3) Is this competitive with using parachutes to slow down for splashing into the ocean, and simply using a ship to hoist it out? Such as the shuttle's solid rocket boosters did.
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#19 2026-10-28 07:02:40
- offtherock
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Re: New Rocket Design
yeah i have now moved more towards,
not having a net.
but instead, have some kind of metal structure.
and can attach drones to the metal structure.
that way it can vary, how much pull, the structure can achieve.
then when whatever object is falling, is approaching the ground.
the metal structure
takes off
then falls alongside the falling object.
moves under it.
then gets ready,
then,
at the correct moment,
all rotors, full speed up.
so it will grind to a halt, a few meters above the ground.
then it can land wherever it should.
and a structure like this could be just,
moving up and down all the time.
it would effectively create a piece of land
where objects can freely just let themselves fall
be it someone coming from space,
some stuff tossed from a plane.
or sky divers without parachutes
a safe, fall zone
i think its easier to implement than it sounds.
Last edited by offtherock (2026-10-28 07:07:45)
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#20 2026-10-28 07:28:20
- tahanson43206
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Re: New Rocket Design
For offtherock ...
For our readers who may be interested in how you develop your ideas, please consider using the image capabilities of Gemini or ChatGPT or CoPilot or your favorite AI assistant.
I think you will find that these assistants have evolved to the point they can show what you have in mind.
They can also help you find examples from history of anyone trying any of these ideas.
If you ** do ** find such examples they might be of interest in your topic.
They might show concepts that work or perhaps ones that were tried and set aside.
One company tried catching rocket bodies with a helicopter.
the US Air Force famously caught canisters of film during the Cold War.
You can save images on imgur.com. There is a limit to the number you can save but it is a generous amount.
(th)
Last edited by tahanson43206 (2026-10-28 07:29:51)
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#21 2026-10-28 07:46:35
- offtherock
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Re: New Rocket Design
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#22 2026-10-30 04:38:44
- offtherock
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Re: New Rocket Design
it could also be used,
to just, let cargo out of a plane
and the drone will make sure its delivered,
precisely where its headed.
it would be like,
next level delivery
and super cheap
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#23 2026-10-30 04:55:03
- offtherock
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Re: New Rocket Design
yeah maybe a net.
placed on a metal frame.
https://chatgpt.com/share/6ae47761-68f8 … 20711bf7c9
its really split in 2.
its external structure
and internal structure
the external structure,
is what does the lifting
thats where the rotos are, the battery etc.
interal structure,
is whats being carried.
maybe that should just also be,
the same type of metal structure.
its just that
the drone can land.
and then release the internal framework.
fly away.
internal framework sits there.. with cargo.
and u can just..
remove cargo
put in another cargo
then drone lands again
fastens internal framework
off it goes.
its basically a transportation system.
yeah but who is ever going to need a transportation system.
the idea is dead in its tracks.
its a transportation system.
which happends to also catch things falling from the sky.
and drones can exchange cargo mid air by just, releasing the cargo
falling
go underneath each others cargo.
thats it.
maybe were kinda like these guys.
https://www.youtube.com/watch?v=SMTDQZzQMKk
or i feel kinda like that sometimes.
i wished we could 3d print ideas
could just,
right click image with concept
press print
and it implements it.
Last edited by offtherock (2026-10-30 06:21:09)
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