Solid boosters

Those might be the logical next step, when going orbital, wouldn't they?

Did John ever mention an interest in developing them?

Why would you go from a very good working knowledge of liquid boosters to solids of which they have little experience?

The armadillo concept draws a lot of philisophical momentum from the Otrag concept which relied on keeping everything similar to keep costs down.

Yes, but solid-state boosters are easy and cheap to build (many amateur rocketists do so) and it makes the whole prospect a lot easier if you can get an extra, big push at the start.

If something goes wrong, an SRB can't be shut off or throttled for a controlled landing. This is probably a major safety issue for Armadillo, since they plan to have manned launches.

Well, I can think of a few things to counter that.

The simplest one is probably to cut off the top of the solid booster, so to say, and anchor it beneath some solid part. A channel and cup arrangement makes that even simpler. And you can add an igniter to fire the top at will. That has two advantages:

1. If the solid booster is spend, the pressure at the top will automatically discard it.

2. If there is an emergency, you ignite the top and the booster is discarded.

And if you want vector control, you add a pack of small, solid charges. Which can be used to rotate and push the booster to the side as well.

But a controlled landing when something goes wrong at the start would require discarding everything but the last stage anyway, unless they add a (generally solid-fuel) escape booster at the top of the module. And even then.

Cut off the top? How?

Steering charges? How many charges?

Where do you see people building solid fuel rockets like that in real life?

Incase you have not noticed your simple to build solid fuel booster suddenly has gotten a lot more complicated and now has additional failure modes to boot.

Building more of the same liquid fuel modules amkes a lot more sense than starting an entire new development program.

Imho Solid Rocket Boosters make absolutely no sense at all on a rocket with throttled engines.

A solid can be shutdown. Extinguish the flame with Halon and it's out. You can’t throttle it but you can design the grain to provide nearly any performance curve you could want. Gimbaled guidance works just as good on a solid. The Shuttle SRB's are gimbaled and steerable. We now even have a solid fueled Lander that is functioning the "Quad Pod" It will be switched over to liquid but it can be done. Our blog has a picture of it. www.teamprometheus.org as soon as I get time there will be some new pages on our site (with video) describing all the new stuff we are doing.

Monroe

Solids are dangerous so why no just go half the way and make a hybrid engine like Scaled or CS. Peter Madsen from CS has linked to this text on the pros and cons of hybridengines

http://www.stanford.edu/~cantwell/AA283 ... ockets.pdf

yours Marius

I doubt AA will go to solids. I know we never will. They have very few advantages and a whole lot of drawbacks.

Hybrids have most of the drawbacks of liquid engines plus most of the drawbacks of solid engines, so that's a dead end too.

Really, once you have the experience to design and build liquid fueled rockets, it's easier to just build a bigger one than it is to strap a bomb on the side.

The first stage of the new NASA Ares rocket is basically a modified shuttle SRB. The rocket nozzle is gimballed to provide attitude control for the rocket. Solid rocket motors are very simple, and in my opion, much safer than hybrids or liquid fuel rockets. The propellant is very safe to handle and store.

The main issue is that solid rockets cannot be throttled or easily stopped once they are started. That is why liquid fuel engines are needed in addition to the solid rocket booster.

Dave

And it's ridden with problems. For example, due to unthrottabibilty of the solid stage, Orion ships has to be uquipped with very heavy escape motors which adds mass.

Then thera are heavy vibration problems.

The main reason they (NASA) use SRB based first stage is because they have working and well tested SRB production & deployment arrangement, and they want to keep that going after Shuttle retirement.

rgds
\Seb

There's a long discussion on this elsewhere, but in short, there's a significant history of solid rockets causing nearly instantaneous total loss of vehicle, whereas liquids fail much more benignly.

Since this is a new solid rocket, they can not realistically claim that it will be more reliable than any other solid rocket, which means that one of the first two hundred flights will likely be lost catastrophically. If it makes that many flights.

You're better off going with pressure fed H2O2/Hydrocarbon biprop engines. Higher Isp, only a little bit more complex, and can be throttelled.

So, if solids are so awful, why are people (Shuttle, sounding rockets, ICBMs, Atlas V) still using them?