Micro-Rocketry to Orbit?

[strangequark]

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?

Haha, sorry I was trying to make a joke that may have fallen flat on the internet. I meant the Isp for peaches and cream would be terrible. HC with Peroxide is decent for Isp.

Honestly, what it comes down to is that I don't think HTP really gains you all that much, compared to more developed systems. It's not that it's bad, it's that the trade isn't positive enough.

[john smith 19]

Honestly, what it comes down to is that I don't think HTP really gains you all that much, compared to more developed systems. It's not that it's bad, it's that the trade isn't positive enough.

The primary drivers for the switch in the 1960s were performance and long term (*decades*) storage. Part of why France achieved orbital launch years before the UK. Everything else was irrelevant primarily to the military planners who wanted these systems.

At the same chamber pressure and nozzle size conditions the amines win. This is undisputed. The storage position is more debatable.

HTP does degrade back to water an O2 with a pressure increase. Permanently sealed tanks without pressure relief would be highly dangerous. However a number of materials are known to be *much* less affected by the process and much less prone to catalyzing it. Tin served as an inhibitor and and it is possible to "passivate" surfaces by flushing systems with HTP before filling, as was done with Inhibited Red Fuming Nitric Acid or IRFNA (another popular oxidizer before the hydrazines).

General Kinetics noted the Syncomm 2 satellite used HTP form 1963-1969 without problem, as did the X15.

BTW NTO is pretty corrosive and will happily attack soft seal materials, and your lungs. 

If you're military or LLNL then Hydrazine is fine. It's hazards are known and factored into your costs.

Outside these groups any one looking to experiment will look at the $60/lb costs of Hydrazines, the WMD level of toxicity and consider the performance is (usually) not worth the risk.

In the context of "Micro rocketry" implying smaller developers might like to make attempts the costs and danger (I would suggest) far outweigh the performance benefits.

Note John Whiteheads "Mockingbird" SSTO was an HTP design and they have mentioned that their design work for the JPL funded micro pumped systems were developed in high pressure Helium and HTP because it let them do more runs in a *normal* laboratory environment rather than suiting (it's not the pump, it's the gas generator that's the issue).

For an experimental "micro rocket" I'd say the first objective is to build something a small team can handle and find out it's payload *after* it's built.

Outside military systems and space probes storage time is not a very relevant parameter to consider. If you did the *obvious* answer is to go to solids, which the USAF starting with Minuteman and the USN with Polaris.

With the exception of Orbital Science Corp I don't see anyone rushing to follow.

[mmeijeri]

Honestly, what it comes down to is that I don't think HTP really gains you all that much, compared to more developed systems. It's not that it's bad, it's that the trade isn't positive enough.

Well, that depends on the application as John suggests. For use in an RLV HTP seems more practical than hydrazine, since you would have to load and safe the vehicle many times. HTP (or NOFBX once proven safe and reliable) would probably also be preferable for a crew taxi, except in the short run, which is why I assume Boeing and SpaceX went for hypergolics.

But I think you are right for spacecraft that don't return to Earth. I see no rush to replace traditional hypergolics with something less toxic or corrosive in that field. To the degree there is an urge to use HAN / ADN it seems to be driven more by a desire for higher Isp than monopropellant hydrazine than by a desire for better handling characteristics.

[Ed LeBouthillier]

Randy said:

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

I've also started a blog to develop ideas related to small launch vehicles. You can find it here:

http://orbitalaspirations.blogspot.com/

Cheers,
Ed L

[strangequark]

(or NOFBX once proven safe and reliable)

Don't hold your breath. From the information available on that propellant, I suspect a bipropellant would be more reliable, safer, and less complex. If someone from Firestar would care to correct me, I am willing to learn, but that is my impression thus far.

But I think you are right for spacecraft that don't return to Earth. I see no rush to replace traditional hypergolics with something less toxic or corrosive in that field. To the degree there is an urge to use HAN / ADN it seems to be driven more by a desire for higher Isp than monopropellant hydrazine than by a desire for better handling characteristics.

That is correct. The easy handling characteristics of HAN are lagniappe, and it's the Isp that is really driving that. For this topic, that is almost a negative, because the reaction temperatures drive you to exotic materials.

As far as pulling this back to micro-rocketry, my propellant choice, if I were head designer, would be biprop N2O with Ethanol. They're widely available, pretty safe to handle (if you respect the N2O), and have respectable performance. It's not hypergolic or catalytic, but if you weren't picky about ignition time, you could use an acoustic igniter with the nitrous and not have to use pyro. Alternatively, thermal decomp of nitrous isn't too hard, and the required heater is a pretty inexpensive, off the shelf part.

[mmeijeri]

As far as pulling this back to micro-rocketry, my propellant choice, if I were head designer, would be biprop N2O with Ethanol.

Any specific reason to prefer N2O over HTP or ethanol over IPA?

[A_M_Swallow]

As far as pulling this back to micro-rocketry, my propellant choice, if I were head designer, would be biprop N2O with Ethanol.

Any specific reason to prefer N2O over HTP or ethanol over IPA?

HTP can be made from water so it can be made by an ISRU process on the Moon.

[tnphysics]

As far as pulling this back to micro-rocketry, my propellant choice, if I were head designer, would be biprop N2O with Ethanol.

Any specific reason to prefer N2O over HTP or ethanol over IPA?

As for N2O, it

-is non toxic (though an anesthetic in high levels, where high means percent)
-is not decomposed by most metals AFAIK

[Enthalpy]

There I suggest a small launcher that puts 300kg on Leo:
http://saposjoint.net/Forum/viewtopic.php?f=66&t=2527&start=20#p35066

By far not the smallest possible launcher, but small in the sense that it's built around the smallest engine that enables reasonably a single stage to orbit (SSTO) - an RD-0146, heir of the RL-10 but with a roll actuator.

Much smaller is possible of course. As you probably don't want to develop optimized pumped engines just for the micro-launcher, solids or pressure-fed oxygen+fuel would be the choice.

Marc Schaefer, aka Enthalpy

[Enthalpy]

The physical limit is the atmospheric drag, so I've made a quick-and-dirty spreadsheet to evaluate it.

The spreadsheet finds properly that air drag is tiny at normal-sized launchers, like 50m/s performance wasted by Vega, which is compact but accelerates strongly. That explains why Energiya or the SSTL were as streamlined as a cathedral.

The limit is around 100kg lift-off mass, with D=0.3m and 10+8m/s² acceleration and a good Cx=0.25. This wastes significant 270m/s.

Or around 10kg lift-off mass, with D=0,14m and 10+6m/s² acceleration and a good Cx=0.25. This wastes 500m/s, which hurts. Leaves you maybe 200g in orbit, depending on the propellants.

BUT if you start from an old MiG-21 or MiG-25 or F-4 Phantom, at 18,000m height, air is 10 times thinner, so your launcher can be 10 time smaller in each dimension, or 0.01kg. The aircraft even provides the 400m/s lost to air drag. And the launcher can have small wings, allowing the engine to push less, hence expand its gas more efficiently. Reasonable for small launchers.

Then, an other limit is the mass of the tanks or the casing, as thinner walls get impractical. At D=0.2m and 50b, good steel would be around 0.4mm thick. Good aluminium, at 2mm, is less efficient but can go a bit farther.

At solids, you need a minimum insulator thickness inside the casing, like 10mm.

In other words: the limit is set by the sensors, the transmissions, the ability to control a craft with fast reactions...

[Ed LeBouthillier]

The physical limit is the atmospheric drag, so I've made a quick-and-dirty spreadsheet to evaluate it.

The spreadsheet finds properly that air drag is tiny at normal-sized launchers, like 50m/s performance wasted by Vega, which is compact but accelerates strongly. That explains why Energiya or the SSTL were as streamlined as a cathedral.

Would you mind discussing the techniques you used for determining the aerodynamic losses? I've been looking at a good way to visualize the relationship between size and aerodynamic losses. I'm curious about how you went about discovering it.

Thanks,
Ed L

[Rick M]

This site might be of interest :-

http://sugarshot.org/

It is almost the opposite in that very low grade propellant (sugar and potassium nitrate)  is used and the goal is to reach 100km rather than orbit.

We had two motor CATOs on our 120,000' DoubleSShot static motor tests but believe we know the cause after post anomaly testing and will soon be doing our next test. Ed did some calculations that showed we could get a sugar powered rocket to orbit; a 'SSTO' meaning Sugar Shot to Orbit with 5 stages and a tiny payload ( :

[meekGee]

Nice looking solid motor core.

I love the guy running away from the rig (at T-5) like Wile-E-Coyote after lighting the fuse on an ACME rocket.

[RanulfC]

Necro-Threading but thought I'd update that a similar discussion is now here:
http://forum.nasaspaceflight.com/index.php?topic=31135.0;all

Randy

[cpooley]

Microlaunchers is based on starting with a roughly 120 kg GLOW and a 100-200 gram spacecraft to escape, to photograph a NEO and play back stored images over rest of 1st year via laser diode.

Most of the losses relative to small size are with the 1st stage.  The 3 or 4 stage rocket can be partitioned to have the 1st stage just clear the atmosphere.

In vacuum, even very small rockets are nearly as good as "conventional" size.

Starting with escape makes sense because there's no future in crowding LEO space, and LEO is not exploration anymore.

[QuantumG]

Welcome back Charles. Perhaps you could work with Ed LeBouthillier and put together one of his awesome diagrams to explain the concept.