Author Topic: Introducing Firefly Space Systems (Read 346496 times)

kkattula · « **Reply #40 on:** 01/11/2014 07:07 am »

That rocket looks surprisingly wide for a small launcher, they're usually much thinner, for aerodynamic reasons. Which makes it harder (more expensive) to achieve high mass ratio, etc.

If Firefly are attempting to develop a very low cost, expendable, micro-sat launcher, they may be planning to side-step much of the aerodynamic issue by delaying supersonic flight until they're at high altitude:

<SWAG>They lift-off under rocket power, and when they reach Mach 0.6 to 0.8, at 1 to 2 km, throttle back & switch on ramjets or a ducted rocket mode, to maintain that 'cruise' speed. At 15 to 20 km altitude (maybe even higher), they throttle up and continue to staging and orbit. </SWAG>

I've modeled it using only rocket engines, and the increase in gravity losses is only a little more then the reduction in drag losses. Throw in air breathing cruise engines, an altitude compensating first stage nozzle, and an emphasis on low cost...

Also, the air inlet design is vastly simplified by only having to work at a fixed speed.

simonbp · « **Reply #41 on:** 01/12/2014 02:05 am »

Quote from: kkattula on 01/11/2014 07:07 am

<SWAG>They lift-off under rocket power, and when they reach Mach 0.6 to 0.8, at 1 to 2 km, throttle back & switch on ramjets or a ducted rocket mode, to maintain that 'cruise' speed. At 15 to 20 km altitude (maybe even higher), they throttle up and continue to staging and orbit. </SWAG>

That is an even more interesting speculation. Ducted rockets are tricky to properly utilize (need a very specific trajectory), but can really add a lot of impulse if the vehicle is optimized for them. The Soviets got really close to actually deploying one as an ICBM, but the death of the project leader got in the way....

http://astronautix.com/lvs/gnom.htm

RanulfC · « **Reply #42 on:** 01/14/2014 03:46 pm »

Quote from: ChrisWilson68 on 01/11/2014 05:37 am

Quote from: RanulfC on 01/10/2014 08:08 pm
Sea-Bee the world FIRST RLV that was actually REUSED for multiple flights!

Sea Bee was sub-orbital. RLV normally means orbital. An Estes rocket is an RLV is you don't have an orbital requirement.

Direct quote from the website, so take it as you will

Randy

a_langwich · « **Reply #43 on:** 01/15/2014 07:35 am »

Quote from: simonbp on 01/12/2014 02:05 am

Quote from: kkattula on 01/11/2014 07:07 am
<SWAG>They lift-off under rocket power, and when they reach Mach 0.6 to 0.8, at 1 to 2 km, throttle back & switch on ramjets or a ducted rocket mode, to maintain that 'cruise' speed. At 15 to 20 km altitude (maybe even higher), they throttle up and continue to staging and orbit. </SWAG>

That is an even more interesting speculation. Ducted rockets are tricky to properly utilize (need a very specific trajectory), but can really add a lot of impulse if the vehicle is optimized for them. The Soviets got really close to actually deploying one as an ICBM, but the death of the project leader got in the way....

http://astronautix.com/lvs/gnom.htm

Very interesting. An Isp of 550 is quite impressive, even more so for a solid. This air augmentation sounds like good juju. I wonder what would happen if you redesigned Pegasus, or the StratoLaunch rocket, to use air augmentation and adjusted the flight profile accordingly?

For that matter, surely it works on liquid and hybrid engines as well, and maybe SpaceShip Two would be another potential beneficiary. Well, okay, not SpaceShip Two because they don't have time, but SpaceShip Three or Four.

Hmm, this "specific trajectory" doesn't happen to involve high heating like an airbreathing SSTO, does it?

Jarnis · « **Reply #44 on:** 01/15/2014 11:47 am »

Well, it kinda has to.

If you want to get usable amounts of air from the atmosphere, the air obviously will also generate drag and as speed goes up, friction & heat.

No friction, no heat issues but also no air.

It will be an interesting thing to figure out - weight of heat shielding vs. benefit of "free" oxidizer, considering trajectories and altitudes etc.

I'm sucker for any new ideas people are willing to try in practice but I do feel there is a "danger Will Robinson" element here - the narrow altitude band where you get something useful out of the atmosphere without the drag and friction ruining your day may a big problem; I think it was Elon Musk who commented about the theoretical use of air-breathing rockets in first stage, basically saying "why even try to use air out of the atmosphere, you want to get out of it as quickly as possible".

ChrisWilson68 · « **Reply #45 on:** 01/15/2014 09:02 pm »

Quote from: Jarnis on 01/15/2014 11:47 am

It will be an interesting thing to figure out - weight of heat shielding vs. benefit of "free" oxidizer, considering trajectories and altitudes etc.

Actually, technically it's free reaction mass, not free oxidizer. A ducted rocket uses the air as reaction mass only, it still caries all its own oxidizer.

simonbp · « **Reply #46 on:** 01/16/2014 02:05 am »

Right, it's the same basic principle as a turbofan jet, but rather than using a fan, the ducted rocket is directly entraining the air in the exhaust. Since higher thrust is needed when the rocket is low altitude (where there is more air), the thrust from the duct is quite useful.

Jarnis · « **Reply #47 on:** 01/16/2014 06:33 am »

Thanks for the correction. Now that I think about it more, yeah, you are quite right.

It also means the design then makes more sense.

Still I guess there is a careful tradeoff going on (drag/heating vs. benefits from the duct)

TrevorMonty · « **Reply #48 on:** 01/16/2014 08:14 am »

Interestly they have chosen to setup their R&D in Hawthorne, maybe they are looking at recruiting a few SpaceX staff.

RanulfC · « **Reply #49 on:** 01/16/2014 02:53 pm »

Some slight corrections on "Air Augmented Rocket" engines:

They are MOST useful between zero and around Mach-2 IF they are only "augmenting" the thrust. Most often they simply entrain extra air but they CAN use fuel rich exhaust and act as an "after-burner" but these usually require longer ducts, and have increased drag and thermal issues. If designed properly they can and do act as "Ejector-ramjets" allowing use up to around Mach-4 to 6 depending but the trajctory then has to be shallower to accomodate longer air-breathing time.

From the illustration I don't think AAR is what they are using. An AAR set up has the engine surrounded by the "duct" which hangs down below the exhaust so that the exhaust "entrains" the air and has "intakes" all around the duct front which is usually slightly above the engine.

Frankly we're going to need a lot more information than we have, so this is to YOU Firefly; give us more!

Randy

go4mars · « **Reply #50 on:** 01/31/2014 02:35 pm »

So a pseudo-thrust augmented aerospike, until it gets up to "ramming speed", then after ram mode, staging and RTLS? Or is aerospike combined with ram-jets at varying efficiencies the whole time in a seamless continuum?

Is ram aerospike to get around TAN patents? Or does aerospike work more congruently with ram jets?

Danderman · « **Reply #51 on:** 01/31/2014 03:19 pm »

It would be really great if people would put their designs in some other thread, and leave this thread to updates about Firefly systems.

R7 · « **Reply #52 on:** 02/15/2014 06:09 pm »

The site has updated a bit. Still no technical details but more on job opportunities.

http://www.fireflyspace.com/career-opportunities/

bad_astra · « **Reply #53 on:** 02/18/2014 04:12 pm »

Getting awful crowded in my sky.

Sorry.. always wanted to say that in a Firefly thread.

dragon44 · « **Reply #54 on:** 02/18/2014 07:41 pm »

Quote from: TrevorMonty on 01/16/2014 08:14 am

Interestly they have chosen to setup their R&D in Hawthorne, maybe they are looking at recruiting a few SpaceX staff.

They have an address now on their webpage http://www.fireflyspace.com/. They are on the same street as SpaceX. Walking distance

R7 · « **Reply #55 on:** 05/05/2014 07:11 am »

Webpage got some vehicle data:

http://www.fireflyspace.com/vehicles/

Jarnis · « **Reply #56 on:** 05/05/2014 10:15 am »

400kg to LEO is kinda tiny... Reminds me of Falcon 1.

Works as a practice rocket, of course. SpaceX started the same way.

dror · « **Reply #57 on:** 05/05/2014 10:48 am »

It's a nice looking rocket!
Not air augmented though.
So what advancement does it represent?

QuantumG · « **Reply #58 on:** 05/05/2014 10:55 am »

Pressure-fed to orbit, eh. Seems kinda pre-SpaceX.

JBF · « **Reply #59 on:** 05/05/2014 11:05 am »

A full size aerospike. This will be fun to watch; I've been hoping for some more development on them.