Talk:Green Propellant Infusion Mission

Falcon Heavy?
Is this payload actually scheduled for launch on a Falcon Heavy? I don't see that on the launch manifest. &mdash; Gopher65talk 17:00, 5 August 2014 (UTC)


 * Yes, it is piggy-backing as a secondary payload on a Falcon Heavy. Ref: http://www.nasa.gov/sites/default/files/files/GreenPropellantInfusionMissionProject_v2.pdf
 * Cheers, BatteryIncluded (talk) 18:15, 5 August 2014 (UTC)
 * Do we know which one? &mdash; Gopher65talk 18:55, 5 August 2014 (UTC)
 * Hello Gopher. It will be the launch #2 called: Space Test Program 2 (STP-2) which is a Falcon Heavy demo flight for the US Air Force, and since the Green Propellant Infusion Mission (GPIM) development team includes the U.S. Air Force, it will be launched on the demo flight. So, I believe the GPIM is the only payload, but it is of secondary importance to the test flight STP-2. An anon user deleted the GPIM launch info from the Falcon Heavy article and I was just not in the mood for an edit war. Cheers, BatteryIncluded (talk) 01:56, 6 August 2014 (UTC)


 * Looks like it should be added back to the Falcon Heavy page. I just (a moment ago) responded to a question on my Talk page from Gopher65, telling what I know about it.  It appears that BatteryIncluded has an up-to-date source for the FH launch vehicle.


 * Flying the GPIM as a secondary payload makes sense, as probably a wide variety of geocentric orbits would work just fine for doing the testing NASA wants to accomplish with GPIM. Cheers.  N2e (talk) 02:00, 6 August 2014 (UTC)

Propellant section chemistry wrong
The "Propellant" section says "AF-M315E transforms into nontoxic gasses like water vapor, hydrogen and carbon dioxide (CO2)". It is impossible for AF-M315E, aka hydroxylammonium nitrate to transform into carbon dioxide since it contains no carbon.

It also says, "additional oxygen is provided for combustion". This is not true when hydroxylammonium nitrate is used as a monopropellant. The GPIM mission uses hydroxylammonium nitrate as a monopropellant. Additional oxygen for combustion would only be relevant when hydroxylammonium nitrate is used in combination with another fuel component. n It is also irrelevant that the melting point is lower than that of ammonium nitrate since ammonium nitrate is not used as a rocket propellant. Instead it needs to say something significant about the melting point or other properties of hydroxylammonium nitrate.

7802mark (talk) 23:58, 10 February 2015 (UTC)


 * good catch! The reference states "only throws off nontoxic gasses like water vapor, hydrogen and carbon dioxide", but unless there is an additional secret component, there is no source of carbon to produce carbon dioxide. Maybe the reporter got it wrong. I deleted the entry. Cheers, BatteryIncluded (talk) 01:13, 11 February 2015 (UTC)
 * Monopropellant are only kinda "mono". They require a catalyst to "burn" (or decompose, or whatever you want to call it). The catalyst often used for the monopropellant in question (HAN) is 1,3-Butadiene, which has the chemical formula of C4H6. That's where the carbon comes from to make CO2. I don't think that's what this mission uses, though. So I still think the reporter might be wrong.


 * The Monopropellant article has a bit more information, but Wikipedia is pretty lacking in general about monopropellants right now. Or at least the cross referencing is lacking enough that it's hard to find anything.


 * Sources: GPIM Propulsion System, and the Wikipedia HAN article I linked earlier. &mdash; Gopher65talk 01:38, 14 February 2015 (UTC)


 * No, 1,3-Butadiene is not a catalyst for HAN. I think this is a confusion with the case where HAN is used in solid rocket fuels, where 1,3-Butadiene is one of the starting materials for the binder polymer, hydroxy terminated polybutadiene ( HTPB). &mdash; 7802mark (talk) 17:28, 28 February 2015 (UTC)


 * A catalyst also isn't consumed in a reaction, it just facilitates it, so carbon shouldn't be coming from the catalyst, either. I think the reference is wrong on this count. -- Benjwgarner (talk) 22:49, 22 October 2016 (UTC)

New Sources of Relevant Information
US Patent Application US20110165030 A1  appears to contain information relevant, as background, to this article. In particular, it implies that the AF-M315E propellant used in the GPIM mission may not be pure HAN. It may include various other compounds, some of which contain carbon. This would invalidate my objection of 10 February 2015, regarding the presence of carbon.

The patent application says that in monopropellant applications, HAN "is typically combined with water and a fuel. Examples of materials used as the fuel are triethanol ammonium nitrate, 2-hydroxyethyl hydrazine nitrate, hydroxylamine (free base), diethylhydroxylamine (free base), dimethylhydroxylammonium nitrate, diethylhydroxylammonium nitrate, and others."

The Spores, Masse and Kimbrel article, "GPIM AF-M315E Propulsion System" https://www.rocket.com/files/aerojet/documents/Capabilities/PDFs/GPIM%20AF-M315E%20Propulsion%20System.pdf,  indicates that the catalyst for the GPIM thrusters is Aerojet LCH-240. The patent application indicates that LCH-240 is composed of "5% iridium on hafnium oxide" pellets contained in an electrically conductive solid foam.

Another potentially relevant source is T.W. Hawkins, A.J. Brand, M.B. McKay, M. Tinnirello, "Reduced Toxicity, High Performance Monopropellant at the U.S. Air Force Research Laboratory",  AFRL-RZ-ED-TP-2010-219   http://www.dtic.mil/get-tr-doc/pdf?AD=ADA522113

7802mark (talk) 05:05, 16 May 2015 (UTC)

Nontoxic
In the image caption, HAN/AF-M315E is referred to as "a nontoxic ... liquid", but in the HAN article it's referred to as toxic, corrosive and possibly carcinogenic. The reduced toxicity is only in relation to hydrazine and similar fuels. Mainly that it doesn't produce toxic vapour when being handled, either directly or by reacting with handling materials. It doesn't refer to the material itself. Can I suggest removing the word "nontoxic"? (The "reducing the toxic handling concerns" in the article proper seems perfectly reasonable.) -- PaulxSA (talk) 15:58, 1 December 2015 (UTC)


 * Done. Good catch and thank you. BatteryIncluded (talk) 17:00, 1 December 2015 (UTC)

So it is only an improvement over monopropellant hydrazine? not UDMH+N2O4
So I have this straight, HAN's specific impulse gives it a performance-edge over monopropellant hydrazine, but the article is deafeningly quiet on the more important question of if HAN has a performance edge over UDMH+N204. As the article reads now, it seems a bit of an apples to oranges comparison, as exactly who or what uses monopropellant hydrazine these days anyway? I thought the logic was, if you're going to involve hydrazine, or its chemical analogs in your spacecraft design - then you might as well "go for broke" and use the high performance bi-propellant formulations, as obviously no matter what, you'll still be dealing with the headache of hydrazine. So get the best " bang for your buck" and go bi-propellant baby!

What is the specific impulse of HAN+N2O4. Knowing the answer to that question is really what will make or break this tech demonstration for anything more than small Reaction control system engines. Which is pretty unfortunate, as I'd like to see a higher thrust, higher performance, lower toxicity and yet still, hypergolic alternative, to UDMH+N2O4. Boundarylayer (talk) 09:09, 5 January 2017 (UTC)