3D renders of the modular booster concept | Propulsion Workgroup | Forum

I have some issues with this design. For one thing, I am somewhat skeptical about our ability to create large, solid-fueled rockets. Apparently, casting large, single-grain solid rocket engines is somewhat difficult and crystal defects can and do result in burn through and explosions and so on, and the fuel itself is likely to be more expensive than the fuel for the liquid fueled design I have advocated in the past. If it looks like we could do it economically and with good results, though, I could probably get behind a solid fueled design. The lack of throttling is still a problem, though. Perhaps we should look into hybrid rockets.

About the inter-stage sections: Are you still planning on those, or does the addition of a single gimbled nozzle replace it?

About the overall configuration: Is there any particular reason why you didn't go with hexagons of 6 modules around a seventh central module? That would eliminate the central open space the current design includes.

About the gimbaled nozzle: Why? Whatever your reason, do you think it justifies the decrease in economises of scale that results from having two types of module, and the added complexity of a gimbaled nozzle?

About the over-all mission plan: It is likely that the mass of the package with the lander, the small boster to put it on a low energy tranfer orbit and any supplies for the manned craft's return trip would be much less than the mass of the CSM, unless it litterally had an entire replacement SM to put it in the transfer orbit and bring the CM home. A smaller launch vehicle configuration for it might be desirable, unless we built the large configuration large enough to pigyback the lander on the vehicle from a previous, orbital launch. After that, we could always have a lunar lander in orbit or on its way, waiting for the next launch. There's some appeal to this, but it would mean a larger launch vehicle.

That's all I've got for now.

Post edited 11:03 am – November 17, 2009 by Rocket-To-The-Moon

In these drawings the interstage sections are simply adapters to fit the stages together. The ISGA (InterStage Gimbal Adapter) that I devised was for the OTRAG style booster concept. It is unnecessary if the central booster has a gimbaled nozzle.

If we went with 6 boosters around the central booster then you end up with space between the boosters which would cause more aerodynamic drag. Also the outside diameter would be almost the same.

How do you propose control without a gimbaled nozzle? The nozzle would be the only different component, the rest of the booster would be the same. If we went with liquid fuel then we could probably control it with differential thrust.

Just so you know, the drawings are intended to serve more as a guide to the modular concept. They don't necessarily have to be solid fueled. I am very open to discussion about solid vs. liquid but I happen to favor solid fuel because it doesn't require a complicated fueling process involving cryogenic fuels. And once built, a SRB can be stored for years before use which would allow us to stockpile more easily. It really comes down to what gives us the least cost per pound to the moon.

Here are some numbers on the specific impulse of the Space Shuttle SRB vs. Main Engines

SRB:

Sea Level: 242 seconds

Vacuum: 268 seconds

SSME:

Sea Level: 363 seconds

Vacuum: 452.5

LOX + Hydrogen definitely comes out on top

"If we went with 6 boosters around the central booster then you end up with space between the boosters which would cause more aerodynamic drag."

This is, I believe, the opposite of the truth.

http://mathworld.wolfram.com/C…..cking.html

Abut the solid versus liquid thing: If we were to go with liquid fuels, I would personally suggst we look at non-cryogenic ones for added simplicity. I personaly like something along the lines of the chemistry used in the original OTRAG rockets. They used fuming nitric acid and kerosene, both of which are stored at ordinary temperatures. This sort of design has efficiency drawbacks, but is cheap and less prlematic to handle than cryogenic fuels. With more powerful (and thus generally more dangerous) room-temperture liquid oxydizers or more enery-dense replacements for the kerosene, I suspect something like this could work quite well. I've also been looking at hybrid rockets recently, and it looks like they might be the sweet spot. With a hybrid roket, you get greater energy density, easer production, throtelability and better overall safty compared to a solid fueled design, with less complexity than a liquid fueled design. If we went with nitrous oxide as the oxidizer, it would be even safr, while a nitric acid oxidizer could be made to be hypergolic with the fuel or some substence injected seperately whenever we want to fire it, simplifieing the ignission system drastically. Either way, the oxidizer is a cheap, readilly avaliable substance that can be store at room temperature. Thoughts?

brmj said:

"If we went with 6 boosters around the central booster then you end up with space between the boosters which would cause more aerodynamic drag."

This is, I believe, the opposite of the truth.

http://mathworld.wolfram.com/C…..cking.html

This was a good find. This was a nice thing to learn. I want to see what I can do with the formation. With in the next few days, I will see if I can come up with some Matlab calculations that can make it easier for us to apply this type of packing. Also, just looking at it, it seems like it would be somewhat simple to throttle this type of configuration for steering the rocket.

On a somewhat relevant note, should I continue with using Matlab? There is a similar open source software called Gnu Octave. Has anyone used it? Was there a voting application we can use with this Forum to determine what is preferred.