Micro-Rocketry to Orbit?

[Hop_David]

http://www.astronautix.com/graphics/n/nots.jpg

Went to the above url and got:
"Due to a persistent denial of service attack, astronautix.com has been taken off line."

That's horrible! Apparently another good resource biting the dust

[john smith 19]

See Appendix A.  They assume 301s (vac) for the 8 low expansion engines and 327s (vac) for the 1 high expansion engine.
If you're wondering how you get 9 km/s or more with that sort of performance and a 1500/75 mass ratio, join the club.

Mathematics is not my strong suite but I'll take a stab at it.

 ln (mass ratio) =delta V /Isp *g

 ln 20 = 9000 / (Isp * 9.82 )

Well my calculator gives an Isp of 305.93 say 306secs

Now Jeff Greason had a rule of thumb that *average* Isp is (Isp at SL +2* Isp at vac)/3 so the sea level ones = (238 + 2*301)/3 = 280

But the high expansion nozzle has *no* SL Isp listed, suggesting high altitude start so it's difficult to see how to integrate this Isp into the average low expansion Isp's.

This sounds like a vehicle that has been trajectory optimized so it will deliver the required average Isp, but you cannot prove it without a full trajectory simulation.

One curious feature of the design is the use of a nose cone. Kare mentions in the report that air drag is a big factor in small vehicles and reducing it is important. There are much better fairing shapes than the cone but I'm not sure it they have smaller surface area (Haack series). They would also be quite easy to manufacture at this scale by metal spinning. It's not clear if they knew this and still went with the cone (less surface area, easier analysis?) The better shape would buy a smaller seamless tank although possibly more difficult to wrap with aerogel.

[RanulfC]

But the high expansion nozzle has *no* SL Isp listed, suggesting high altitude start so it's difficult to see how to integrate this Isp into the average low expansion Isp's.

As I understand/understood it all engines are started at launch the High-Expasion engine is just run at low throttle till it ramps up as the Low-Expansion engines ramp down. That could be wrong though. Given they are running the Peroxide through a catalyst prior to injection of the Kerosene the engine and propellants act "hypergolic" for starting anyway so it wouldn't be difficult to air-start the High-Expansion engine.

One comment on the slides suggests doing away with the "High-Expansion" engine entirly and just going with an "aerospike" expansion ramp using the piston-pump exhaust.

This sounds like a vehicle that has been trajectory optimized so it will deliver the required average Isp, but you cannot prove it without a full trajectory simulation.

I'm not sure it's on the slide presentation or not but I recall talking with Kare during a presentation and he noted that they had actually run the entire flight through POST and several other trajectory simulation programs. He commented that he still believes that someone with the money could "easily" prove SSTO by doing a version of the Mockingbird

One curious feature of the design is the use of a nose cone. Kare mentions in the report that air drag is a big factor in small vehicles and reducing it is important. There are much better fairing shapes than the cone but I'm not sure it they have smaller surface area (Haack series). They would also be quite easy to manufacture at this scale by metal spinning. It's not clear if they knew this and still went with the cone (less surface area, easier analysis?) The better shape would buy a smaller seamless tank although possibly more difficult to wrap with aerogel.

At the time I suspect the cone was easier to model and since about 2/3rds of the "nose-cone" is tank for the Peroxide I suspect it was just generally a better shape for the time. They were also looking at using a "peroxide-fountian" effect for cooling the inner surface of the nose cone should the aerogel not prove effective enough as heat protection so that may also have factored into the design. You'll note the suggest "upgraded" designs become "longer" and the nose cone shrinks as the vehicle gets bigger.

Randy

[john smith 19]

He commented that he still believes that someone with the money could "easily" prove SSTO by doing a version of the Mockingbird

I think he's right.

John Whiteheads team at LLNL have continued to refine the pumped propulsion system and Xcor have a version available. BTW People think Aluminum is not up to making combustion chambers but the Bell Aerospace chamber on the Agena stage (IRFNA/Hydrazine so hypergolic and room temperature) was Aluminum and gun drilled the throat section to create a solid wall so *no* joins between inner and outer shells. I think the body of the chamber was done the same way. I'm not sure if they even needed to anodize the interior (relying on thermal barrier coatings with *big* thermal expansion mismatches makes me nervous). Armadillo Aerospace also use Al chambers.

Getting hold of 95% HTP is AFAIK still almost impossible but a small scale continuous flow concentration plant (to limit the amount of >70% HTP in the system) should be a relatively straight forward task for a competent chemical engineer.

GNC has had nearly 20 years more work so decent quality is much more affordable and aerogels are fairly widely available.

Insofar as Blue Origin have said anything much about the Shepperd vehicle it seems to follow roughly the mockingbird design but is sub orbital.

[RobLynn]

Getting hold of 95% HTP is AFAIK still almost impossible but a small scale continuous flow concentration plant (to limit the amount of >70% HTP in the system) should be a relatively straight forward task for a competent chemical engineer.

Can buy a distillation plant suitable to make ultrapure 99% H2O2 for $18k:
http://www.tecaeromex.com/ingles/destilai.htm

[john smith 19]

Can buy a distillation plant suitable to make ultrapure 99% H2O2 for $18k:
http://www.tecaeromex.com/ingles/destilai.htm

I stand corrected. Handy to start high and dilute down.

Note the classic concern about high strength HTP (85%+) is with so little water to take the heat away it will exceed the peak operating temperature of the preferred catalyst (Silver?)

Catalyst pack prep seems to be a bit of a black art, as Armadillo Aerospace found out. IIRC attempts at using catalytic converter type preforms gave poor results despite being highly temperature resistant and designed to act as the base for catalytic coatings.

It's an area where small scale tests using *carefully* documented materials and processes could yield big improvements.

[RanulfC]

The same company cited above actually makes a FIVE-element catalyst pack that they claim is very efficent and long-lasting. Another company General Kinetics Inc. (http://www.gkllc.com/) has done some good work on both injected catalysts and advanced catalyst packs. They also have some really informative papers on H2O2 applications.

Randy
(Edit: Corrected element screen number on catalyst pack: See:
http://www.tecaeromex.com/ingles/cata-i.htm)

[john smith 19]

The same company cited above actually makes a tri-element catalyst pack that they claim is very efficent and long-lasting. Another company General Kinetics Inc. (http://www.gkllc.com/) has done some good work on both injected catalysts and advanced catalyst packs. They also have some really informative papers on H2O2 applications.

Randy

Those chamber pressures (along with the comment on the PDF about their use on an interceptor) suggest they were part of one of the pumped propulsion projects at LLNL.

That would make them quite a good starting point for someone wanting to try a mockingbird design.

Thanks for the link.

[RanulfC]

The same company cited above actually makes a FIVE-element catalyst pack that they claim is very efficent and long-lasting. Another company General Kinetics Inc. (http://www.gkllc.com/) has done some good work on both injected catalysts and advanced catalyst packs. They also have some really informative papers on H2O2 applications.

Those chamber pressures (along with the comment on the PDF about their use on an interceptor) suggest they were part of one of the pumped propulsion projects at LLNL.

That would make them quite a good starting point for someone wanting to try a mockingbird design.

Thanks for the link.

No problem though I can't see or find any evidence that GK folks worked on or with LLNL. They DO have a good number of LLNL reports on reciprocating piston pumps on this page though:
http://www.gkllc.com/lit-misc.htm

The Interceptor rocket motor is the LR-40 made by Reaction Motors International, the same folks who built the rocket motors for the X-1 and X-15 rocket planes.
Here is the LR-40 presentation:
http://www.gkllc.com/lit/gk-authored/AIAA-2001-3838_History_of_RMI_Super_Performance_90_Percent_H2O2-Kerosene_LR-40_RE-pitch.pdf

It's actually an "in-line" turbopump design and doesn't use a piston-pump and with a thrust of 10,200lbs is probably far to much for a "Mockingbird" vehicle

On the other hand some of the smaller motors might work very well...

Randy

[Proponent]

Attached is a paper the title of which mirrors that of the thread.  If it's already been posted in this thread (I haven't been following it), please let me know, and I'll remove this post to avoid pollution of the thread.  [No doubt someone's thinking:  "Yeah?  So why don't you remove all your posts then?" ]

[john smith 19]

The same company cited above actually makes a FIVE-element catalyst pack that they claim is very efficent and long-lasting. Another company General Kinetics Inc. (http://www.gkllc.com/) has done some good work on both injected catalysts and advanced catalyst packs. They also have some really informative papers on H2O2 a

No problem though I can't see or find any evidence that GK folks worked on or with LLNL. They DO have a good number of LLNL reports on reciprocating piston pumps on this page though:
http://www.gkllc.com/lit-misc.htm


Randy

If you click on the pictures of thrustors on their home page they download a 2 page spec sheet. It mentions why they were developed there. 

"Interceptor" is being used in 2 slightly different contexts. The RMI engine was for a plane, the thrustors were for an interceptor missile.

LLNL was very much the birthplace of SDI and the idea of kinetic energy kill vehicles under the Brilliant Pebbles programme.

Thrustors of this thrust level are normally pressure fed but *much* larger due to lower chamber pressure (100-150psi) needing some kind of pump.

Scaling effects worked out at LLNL indicated turbo pumps scale badly below 5000lbs so a reciprocating pump was the obvious alternative, given the defense application. Smaller thrustors -> smaller missile (or more propellant) -> better tracking of maneuvering target.

[RanulfC]

Thanks Proponent, interesting paper!

John Smith 19:
Ok I understand what you're getting at now. I DO suspect that piston-pumps would be better for a smaller vehicle.

I just wish there were more "vendors" for smaller, high thrust rocket engines.

Oh have you looked at the website for Frontier Astronautics?

Randy

[john smith 19]

Thanks Proponent, interesting paper!


John Smith 19:
Ok I understand what you're getting at now. I DO suspect that piston-pumps would be better for a smaller vehicle.

I just wish there were more "vendors" for smaller, high thrust rocket engines.

2 words. "Limited market." Most of these are used on satellites where people are *very* cautious on new hardware, especially commsats where a station keeping thrustor failure will cost *billions* in lost revenue over say a 10 year life. Today they are *all* pressure fed hypergolics with NTO and MMH/UDMH for performance and are not really volume restricted in the way missiles are. No pressure to evolve the technology.

They may also be worried about the bogeyman of HTP decay in the tanks. GK mentioned in one of their papers defending HTP that the Syncomm2 satellite ran 1963-1969 using HTP attitude control with 1960's quality HTP. We *should* be able to do much better today with higher concentrations and lower impurities (both very good for long term storage) *provided* proper materials selections are made.

HTP takes a performance hit at the *same* chamber pressure (but does not cost c $60/lb or need a full body suit to work with it)

I'm not sure if you fully understand that smaller chamber *needs* higher pressure and no one commercially wants that as higher pressure -> heavier tanks, *unless* you go to a pumped solution, which lowers tank pressure (LLNL pumped demonstrator used MMH and Titanium tanks 0.5mm in thickness) but is untried on orbit. For small vehicles it's all about mass per unit of surface area, either the tanks or the chambers.

A comment in one of Whiteheads papers from LLNL was to the effect that the exploration community had relied on these for their main delta V engines on large space probes (to places like Jupiter and Saturn) but that it should start looking to their own thrust chambers (at higher pressures) to give better efficiency in future large missions.
   
In the big aerospace world the nearest thing for this was the Rocketdyne LEAP thruster, using mixed oxides of Nitrogen fuel.  This also ran c500-1300lbs of chamber pressure, which suggests a pump drive, but no details of the drive system were given.

The DoD runs a thing called the "Space Test Program" which test US and foreign space hardware. Potentially this allows new vendors a "qualification" flight so you can demonstrate your hardware works IRL.

Oh have you looked at the website for Frontier Astronautics?

yes. I think I met them some years ago at Space Access, when they are getting started. They've made impressive progress.

[RanulfC]

Interesting little web-site I ran across:
http://home.earthlink.net/~apendragn/atg/qp/

Randy

[strangequark]

HTP takes a performance hit at the *same* chamber pressure (but does not cost c $60/lb or need a full body suit to work with it).

Nope, it just reacts hypergolically with test engineers. Also, since when does hydrazine require a full body suit to work with?

[mmeijeri]

Also, since when does hydrazine require a full body suit to work with?

Do you mean because it is easy to work with once it has been loaded and sealed? Unlike, say cryogens.

[john smith 19]

Nope, it just reacts hypergolically with test engineers. Also, since when does hydrazine require a full body suit to work with?

Probably since the exposure limits for MMH were set at 0.01 ppm and UDMH at 0.5ppm of air. Gasoline at a filling station is around 1000 ppm.

For reference a nerve agent is roughly 60ppm of the mass of a whole person.

Those pictures of techs fussing around some satellite in a clear room are (AFAIK) taken when the sats are *empty*.

This is what NASA calls the gear they use to handle these chemicals and this is what it looks like.

http://www.wolfhazmat.de/astrosuit/nasa_01.htm

It gets the job done but it's scary and expensive.

[mmeijeri]

As I understand it the hypergolics are only dangerous during loading and safing. Once sealed, they're perfectly safe and more convenient to handle than cryogens. That is part of the reason why some people have suggested the use of hypergolics for air-launch. Of course, the cost of the loading and safing may be higher than the savings gained by air-launch.

[strangequark]

Probably since the exposure limits for MMH were set at 0.01 ppm and UDMH at 0.5ppm of air. Gasoline at a filling station is around 1000 ppm.

For reference a nerve agent is roughly 60ppm of the mass of a whole person.

Those pictures of techs fussing around some satellite in a clear room are (AFAIK) taken when the sats are *empty*.

This is what NASA calls the gear they use to handle these chemicals and this is what it looks like.

http://www.wolfhazmat.de/astrosuit/nasa_01.htm

It gets the job done but it's scary and expensive.

I know what a SCAPE suit looks like John . Granted, I may have been a little disingenuous, but my point is that hydrazine in small quantities doesn't require anything more than pvc gloves, eye protection, and a fume hood. People see what HTP requires in smaller quantities (or what was required in the 60s...) and generalize upward, which is not necessarily valid.

I guarantee you that if NASA used HTP in large quantities, they would require PPE just about as bad. Peroxide isn't toxic, but it is damned corrosive and reactive. This forum seems to have a large attraction to HTP, and I suspect it's because it's the devil they don't know. I'm not saying it's a bad propellant, but it's not all peaches and cream either (the Isp on that combo is terrible anyway).

Martjin is correct too, in that hypergols are pretty reasonable to work with if you have everything sealed and are doing automated transfers. There's even a system in work for CubeSats using monoprop hydrazine. The trick is that the system is delivered preloaded, and fully hermetically sealed.

[mmeijeri]

Well, you know me quark, now I have to rush to the defence of peroxide!  Seriously though, is Isp that bad? I thought it was only slightly worse than MMH/NTO. What combination were you thinking of?