Solid, Liquid, or Hybrid?

Looking ahead to suborbital tourism (one of the main goals of Xprize),what do you think the engine type of choice will be? Scaled seems to be betting, at least initially on hybrid. Spacedev is doing the engine work, and they have considerable experience with this, since they bought AMROC's assets.

I see Space Transportion (I forget their exact name.. two guys working in Washington state, though), are working with large solid motors, and most of the rest of the serious teams are working with liquid rocket engines. What do you thinkt the advantages, disadvantages will be for these various engine platorms?

Solids are completely mental. They can detonate at any given moment.

Hybrids are cool, though a little bit akward for the long term.

Mono-liquids have a nasty ability to detonate also.

Orbital stuff really needs h2lox bi-liquids but in the near term liquids are a little bit less handy than hybrids.

My choice would be hybrid if I was building a sub-orbital class ship. The fuel rods are inert on their own and they are pretty handy all around.

I think as a tourism industry begins to actually develop it'll be LOX and Kerosene. After all you can get kero pretty anywhere and from there manufacture the LOX on site. That would give a lot of mobility to a tourist rocket, pretty much to any airport in the US I would think. The regulatory stuff would be pretty 'interesting' though.

I am amazed that no X-Prize teams mention trying to determine whether 50% peroxide would work in the Me163B "Komet" combination of hydrogen peroxide and alcohol (with enough hydrazine hydrate mixed into the alcohol to make it hypergolic with the peroxide).

Try working with hypergolics sometime and then you will know why no one is fooling around with them on this. Also, its difficult enough to get launch permits without using toxic chemicals like hydrazine. Armadillo, however, has done some EXTREMELY cool stuff with mixed monoprop motors.

Advantage of the Xprize are that the requirements are mild enough to not require toxics and cryogenics and all mean and nasty and all kinds of ungroovy things. (And the WFNA and the RFNA and the hairy eyeball sitting next to me on the Group W bench.. Sorry)

ME-163's had a bad habit of exploding, WITHOUT the allies assistance.

...As in when somebody'd screw up and top off the tank... ...With the wrong chemical...


::POOF::


Instant Bar-B-Q.

Im hoping for advent of reasonably storable, non-cryo, and environmentally sane fuels. Solids are pretty much out of the picture though due to their uncontrollable nature.
But Kero+LOX seems like a good choice, various hybrids, peroxide combinations all seem to fit the bill.
Why storable ? To make later orbital refuelling infrastructure alot easier. Hydrogen storage on orbit is just crazy with the boiloff problems. LOX is reasonably doable, hybrid cores would be a relative walk in the park although the refuelling operation itself would be more complicated.
I think orbital refuelling depots will be essential component of space transportation infrastructure, it would also create a cool niche market of orbital fuel delivery, which is ideally suited for ultra-cheap expendable rockets.

I think that hybrids and liquids will offer the same level of on orbit refueling difficulty. When refueling is spoken of, most people think of what you do at a gas station, or perhaps what military aircraft do in flight, that is pumping fuel from one craft to the next.

In zero G this becomes really difficult and moving cryogenics is awful at the best of times. Why not swap standardised tanks out, like oversized batteries? Then hybrids present the same level of difficulty as a liquid tank when moving and installing these things.

The only draw back, is that some tanks (esp. in presssure rockets), the tank may be intergrated and load bearing in order to save weight. So replacable tanks will have a slight weight penalty. This will be madeup however with ease of service and inspection of reusable vehicles that are designed to be pulled apart.

Hydrazine hydrate is not anhydrous hydrazine (i.e., straight hydrazine). Fuel for the Me163B was a 70/30 mix of alcohol and hydrazine hydrate.

Read the book "Ignition" and you'll find out why the admirals never put the "safe nontoxic nonhypergolic noncryogenic" combination of hydrogen peroxide and kerosene (jet fuel) as missile propellants on aircraft carriers.