Talk-Polywell.org

I'm impressed. When I started to read all I could think was "how can anyone hope to compete with SpaceX?" Well, these people can. The only hope for a significantly more efficient engine than what SpaceX is using is really an aerospike. That's what these guys are planning on. The only structures that have higher strength to weight than the Lithium Aluminum friction stir welded tanks SpaceX uses, is filament wound composite, and this is what they plan to use. This same structure is ideal for deep space, as it protects best from radiation because of its high moisture content. And there are reasons to suppose these two stage rockets can be reusable same as the Falcons.

I wish these guys great success. Certainly they're worth keeping an eye on.

http://arstechnica.com/science/2014/11/ ... h-orbit/1/

Firefly has an interesting design. The cooling system is critical. The hurtle that has kept aerospikes from bring used in the materials issue with the plug getting too hot. If they can keep this cool and the self-pressurization (delivery of the fuel to the engine as the tank empties) works out, I think they will be successful. However, they will probably loose a few rockets in the development process. They will need enough financing to cover these losses.

I'd be really curious to learn what sort of margins he has on the basic design. Carbon composite is really light stuff. Much lighter than LiAl. If the tanks can take the pressure they need them to, and still be lighter than LiAl, then SpaceX has serious competition. And if they're strong enough to pressurize like this, they're strong enough to survive reentry, so my guess is he wants to reuse them too. If you can't reuse, Musk will put you right out of business.

Very exciting.

Nice article GT, thanks.
Building small rockets first should help keep the price down. Targeting two years to flight is aggressive for development, but these guys are gung-ho. Fun to follow all these entrepreneurs on the cutting edge... and to watch the old crony dinosaurs squirm.

kurt9 wrote:The cooling system is critical. The hurtle that has kept aerospikes from bring used in the materials issue with the plug getting too hot.

Thanks for this. I was a little annoyed that the article twice raised the question of why aerospikes are not the predominant technology, but both times pretty much glossed over the answer.

Maui wrote:

kurt9 wrote:The cooling system is critical. The hurtle that has kept aerospikes from bring used in the materials issue with the plug getting too hot.

Thanks for this. I was a little annoyed that the article twice raised the question of why aerospikes are not the predominant technology, but both times pretty much glossed over the answer.

Aerospike overheating was one of the two issues that killed X-33/Venturestar. The other was their composite tank delaminated because NASA hired someone who didn't know what they were doing. The engines were overheating badly in simulations, and the response of the engine team was to simply throw their hands up and say they needed some fantastically heavy copper heat sink. The propulsion team more than the tank team killed that project because they decided they just couldn't do the job. Private industry would have fired them but you can bet they still work at NASA.

Operating at the design expansion ratio the classic bell nozzle gives winning performance. The advantage of the aerospike and some other exotic concepts is performance doesn't degrade nearly as much operating off design parameters. This is particularly helpful for a SSTO system that uses the same engine from sea level to orbit. For a 2STO system it's not difficult to use one nozzle with decent sea level performance for the booster and a different nozzle with good vacuum performance for the upper stage.

GIThruster wrote:I'd be really curious to learn what sort of margins he has on the basic design. Carbon composite is really light stuff. Much lighter than LiAl. If the tanks can take the pressure they need them to, and still be lighter than LiAl, then SpaceX has serious competition. And if they're strong enough to pressurize like this, they're strong enough to survive reentry, so my guess is he wants to reuse them too. If you can't reuse, Musk will put you right out of business.

Very exciting.

Haven't kept up with the details of spaceX's design, but why couldn't they adapt to composite tanks too?

Was there something wrong with the thread I started a few days ago? Days without comments, then someone else posts the same article and off the discussion goes?

If people are ignoring what I post, just let me know and I'll stop.

actually, you posted it one day before this thread was posted. Don´t be pissed. Sometimes this kind of thing happens and not even we can explain WHY we only saw this thread but not yours.

I mean... I saw this thread and read it yesterday, but for some reason I missed yours. Why? Wish I knew, however, since I did NOT see it, I don´t know why that happened.

I know however that I entered this thread thinking it was news about the Firefly sci-fi show

https://www.youtube.com/watch?v=JY3u7bB7dZk

Diogenes wrote:

GIThruster wrote:I'd be really curious to learn what sort of margins he has on the basic design. Carbon composite is really light stuff. Much lighter than LiAl. If the tanks can take the pressure they need them to, and still be lighter than LiAl, then SpaceX has serious competition. And if they're strong enough to pressurize like this, they're strong enough to survive reentry, so my guess is he wants to reuse them too. If you can't reuse, Musk will put you right out of business.

Very exciting.

Haven't kept up with the details of spaceX's design, but why couldn't they adapt to composite tanks too?

does he need to?

the composite tanks were listed as a requirement to the possibility of aerospike engines and the reason the X-33 never became a reality.

so Firefly needs aerospike engines. But I don´t see why Musk would need them unless he decides to pursue aerospike engines too.


However, it seems to me Musk has always gone for the "beautifully and precisely simple designs". Cheap, efficient and safe.

Wouldn´t aerospike engines add complexity and make the whole rocket more expensive? Of course, the price of the rocket stops being such an important issue AFTER you have reusable stages. Just then the price of fuel starts being a factor to consider.

SpaceX right now in theory will only be able to land first stage (stages, in the case of Falcon Heavy).

How to make an aerospike engine competitive with a cheaper design that can land it´s first stages? I guess only solution would be to be SSTO (like X33 itself was suppose to be right?).

And lets not forget SpaceX is pursuing that methane engine that will be quite more powerful than the Merlin and they want it to be powerful and economical enough to be used on the 2nd stage too.

hanelyp wrote:Operating at the design expansion ratio the classic bell nozzle gives winning performance. The advantage of the aerospike and some other exotic concepts is performance doesn't degrade nearly as much operating off design parameters. This is particularly helpful for a SSTO system that uses the same engine from sea level to orbit. For a 2STO system it's not difficult to use one nozzle with decent sea level performance for the booster and a different nozzle with good vacuum performance for the upper stage.

I think this is one of the trade studies Gary Hudson did before he started AirLaunch, and what he found was that just the first 30,000 feet makes a huge difference. If you start your engines at 30,000 feet, you start with a very different nozzle.

Carl White wrote:Was there something wrong with the thread I started a few days ago? Days without comments, then someone else posts the same article and off the discussion goes?

If people are ignoring what I post, just let me know and I'll stop.

I missed your post too. I want to believe tough, that I am just way kewl and people like me so they posted in my thread. Please if you find this is not true, don't tell me.

Whatever happened to that jet engine that was under development by the British that used liquid cooling with helium for hypersonic speeds

The last material news was in January when they announced an R&D relationship with the US Air Force Research Laboratory's Aerospace Systems Directorate. The EU have given them a 1M Euro contract for study into next gen space systems. Finally the UK government have announced an investment of £60M/around $100M, much to the delight of people like me who didn't think the UK government could even spell foresight or strategy.

They do appear to have convinced at least some people that they have something worth pursuing.

The website for Reaction Engines Limited has more details.