Project Evolved Reusable Launch System

T.Neo

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Through musings of a Shuttle successor, the future of manned spaceflight, SSTO vehicles, and, uh... nuclear-powered spaceplanes... :uhh:

Comes the Evolved Reusable Launch System concept. It is a VTOVL 1.5 stage-to-orbit vehicle, with (what I'd like to think are) some unique concepts.

The concept is a kerolox (though this isn't set in stone yet, it could be hydrolox if performance demands) vehicle, that keeps its fuel in drop tanks, which it carries nearly to a significant fraction of orbital velocity (feeding the rest of the ascent with internal fuel tanks- the 'second stage' fuel). These internal tanks also hold the fuel for landing, with oxidiser held in highly insulated, boiloff-resistant tanks seperate from the main LOX tank. The LOX tank is retained, as opposed to the RP-1 tank, due to its insulation and boiloff control systems, making it slightly more complex.

Staging engines (similar to the early Atlas launchers) is likely more efficient, due to the fact that engines weigh a lot, are unecessary late in the flight, and are small and relatively rugged, making them easier candidates for recovery than a propellant tank.

Given these factors, the drop-tank staging is meant more for reducing the need for extra mass in TPS systems, OMS and RCS motors, and landing propellant, for returning the RP-1 tanks and their associated infrastructure, than for improving staging and "physics difficulties" overall.

The drop tanks are intended to be simplified, rugged, and set up for mass-production utilising good economies of scale. While one might note that no commercial aircraft uses drop tanks, military aircraft often do, and modern expendable launch vehicles are pretty much drop tanks themselves (and drop payload bays, and drop avionics, and drop engines, etc :shifty:).

RCS is fed by pressurised gas propellants; likely a gaseous hydrocarbon fuel and nitrous oxide oxidiser, instead of toxic and corrosive hypergolic propellants. The orbital manuvering system likely uses a similar mix of propellants, or could even siphon some propellant from the internal oxidiser/fuel tanks, for higher performance.

One of the criticisms leveled at STS has been the fact that it tried to launch satellites and crew on the same flights, incurring an unecessary risk to the crew and an unecessary mass penalty to the satellites. Therefore in this case, manned capability is intrinsically included, but only as an optional component. A space is provided in the nose for a modular pressurised cabin.

When this cabin is removed, its mounting space adds little payload penalty to the vehicle, and can also be used to mount some experiments or static payloads.

Overall payload capability is something like 15 tons; the vehicle is no heavy-lifter, it is instead intended for high flight-rate, high reliability, and the facilitation of orbital construction. Provision for cabin modules is within the 15 ton capability- i.e. they are a payload and will thus eat into other payload availability. There is a potential for several cabin modules- a module for two astronauts or a small crew, a module for a small crew and a good deal of pressurised cargo capability (a la MPLM), and a module for a large passenger complement (dependant on various other factors).


Note: image is a rough depiction only and not representative of any mathamatical calculations, engineering assumptions, or even an absolutely concrete design.


It should be possible to include some sort of LES for escape in the early phase of launch.

Vertical landing could be seen as a problem by some, due to the active nature of the landing system (if your engines fail, you essentially die). However, vertical landing has operations advantages- the vehicle can land on say, a 500x500m concrete platform, have a mobility platform driven up to it, be mounted on the mobility platform, be moved directly to a servicing building, and then be moved directly to the launch site, lowering costs and turnaround times.

Another potential is to add wings and change the position of the landing gear, to create a VTHL vehicle. This would add mass, but also remove the need for landing propellant. It would however complicate launch handling somewhat.

Reentry would likely be base-first, necessitating some plan for shielding the propulsion system. A side-first reentry shouldn't be impossible though, as DC-X/DC-Y showed, but the vehicle has to flip over before initiating powered descent, which could add another factor of unsafety.

Comments, discussion and (constructive) criticism are welcome. Hatred is not, if need be, that is my job. :facepalm: :lol:
 
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Wishbone

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How many launches do you expect from one vehicle (as in - number of launches till forced retirement, not the mean number till blowing up), since this design is driven by eeekonomix?
 

Hlynkacg

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For shielding the propulsion system look at Plug Nozzles on Atomic Rockets. Seems to me that one could adapt it to a Annular Aerospike that closes durring re-entry.
 

T.Neo

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How many launches do you expect from one vehicle (as in - number of launches till forced retirement, not the mean number till blowing up), since this design is driven by eeekonomix?

Obviously your flight rate is defined by demand, you can't push demand up just to raise your flight rate. However, assuming 20 satellite launch flights per year, plus 5 unmanned resupply and 5 manned flights, that is 30 flights per year, or 6 flights per vehicle in a fleet of 5 vehicles. With a maximum number of flights of 100, the original vehicles would reach their service lifetime in some 16-17 years at that flight rate, though I imagine you might be able to stretch that a little longer, if you kept swapping out critical components.

If initial program R&D cost was $20 billion, it would equal out to about $42 million per launch in the first 16 years, or about $2800 per kilogram for a 15 000 kilogram capable vehicle. If the R&D cost was only $5 billion, it would be $10.5 million per launch, or $700 per kilogram. This is not including unit costs or recurring costs.

One of my main skepticisms of Skylon's low cost/kg is that it is partially based on a very high flight-rate, but you can't just push flight-rate up to your liking. Even if you end up with quite a high flight rate relative to existing vehicles, you still have to pay back that R&D cost.

For shielding the propulsion system look at Plug Nozzles on Atomic Rockets. Seems to me that one could adapt it to a Annular Aerospike that closes durring re-entry.

A plug nozzle would be ideal, but it would also mean trying to come up with believable numbers for a whole new engine...
 
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