Author Topic: Monomethylhydrazine Q&A  (Read 2362 times)

Offline Ronpur50

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Monomethylhydrazine Q&A
« on: 02/07/2017 12:18 PM »
I know that Monomethylhydrazine is a very dangerous and toxic to deal with.  But I was wondering what materials it is corrosive to?  Could a leak of it damage spacecraft systems such as solar panels, shuttle tiles or the skin of the spacecraft? Could it damage the spacesuit of an astronaut on EVA as well?

Offline Jim

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Re: Monomethylhydrazine Q&A
« Reply #1 on: 02/07/2017 01:08 PM »
I know that Monomethylhydrazine is a very dangerous and toxic to deal with.  But I was wondering what materials it is corrosive to?  Could a leak of it damage spacecraft systems such as solar panels, shuttle tiles or the skin of the spacecraft? Could it damage the spacesuit of an astronaut on EVA as well?

It isn't an acid.  The risk to the astronaut is when he removes the spacesuit.
It wouldn't affect tiles or skin of a spacecraft. It might discolor solar cells.

Also, you know there is a difference between Monomethylhydrazine and hydrazine?

Offline Ronpur50

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Re: Monomethylhydrazine Q&A
« Reply #2 on: 02/07/2017 01:17 PM »
Thanks, Jim.  About the difference, I know hydrazine has been used as a mono-propellent, while both hydrazine and Monomethylhydrazine is used in two-part systems. 
 

Monomethylhydrazine was used on the Apollo RCS, right?

Is the nitrogen tetroxide more corrosive? 

I am trying to figure out what would happen if these leaked on a spacecraft in orbit and what damage they could cause to the spacecraft.
« Last Edit: 02/07/2017 01:35 PM by Ronpur50 »

Offline Arch Admiral

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Re: Monomethylhydrazine Q&A
« Reply #3 on: 02/11/2017 01:26 AM »
The Shuttle RCS thrusters suffered leaks of NTO in orbit due to corrosion in the valves - a problem that had previously surfaced during Skylab 4. On one of the Shuttle Mir missions, the Russians refused to permit the Orbiter to approach Mir until NASA proved to them that the problem was under control.

For their own shuttle Buran, the Sovs dropped MMH/NTO and used Kero/LOX for the OMS engines and Kero/GOX for the RCS. The GOX tanks were replenished by a LOX gasifier that burned a small amount of kerosene in the LOX. The resulting GOX was contaminated with combustion products that fouled the electric-arc igniters in the thrusters. Allegedly, some thrusters had failed after only two orbits in the only Buran mission - but this has never been officially confirmed since the whole Buran program went down the memory hole.

Most attempts to replace hydrazine and NTO end like this - more trouble than it's worth.

Offline Proponent

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Re: Monomethylhydrazine Q&A
« Reply #4 on: 02/11/2017 09:50 AM »
The Shuttle RCS thrusters suffered leaks of NTO in orbit due to corrosion in the valves - a problem that had previously surfaced during Skylab 4.

Possible nitpick: That was Skylab 3 (2nd crew), wasn't it?

Offline Jim

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Re: Monomethylhydrazine Q&A
« Reply #5 on: 02/12/2017 12:55 PM »
The Shuttle RCS thrusters suffered leaks of NTO in orbit due to corrosion in the valves - a problem that had previously surfaced during Skylab 4. On one of the Shuttle Mir missions, the Russians refused to permit the Orbiter to approach Mir until NASA proved to them that the problem was under control.


The shuttle issue wasn't corrosion but contamination, and it was a issue throughout the shuttle program

And it isn't an issue for most spacecraft, like comsats and planetary probes that have lifetimes of most than a decade.
« Last Edit: 02/12/2017 12:57 PM by Jim »

Offline GWF

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Re: Monomethylhydrazine Q&A
« Reply #6 on: 02/19/2017 05:22 PM »
MMH, hydrazine, UDMH, Aerozine 50 will react with material with high iron concentrations, like stainless steel 440c (used in quad check valves), solenoid magnetic material.  They also react with many types of plastics like pvc, kapton (solenoid insulation) to break them down.  The most common type of soft good in valves is Teflon based and many components are stainless steel or titanium.

Aerozine 50 would permeate and damage our fully encapsulated suits at white sands test facility in under 30 minutes but MMH would have no affect.

In general the hydrazine family is fairly easy to deal with from a hardware side.  Personnel exposure is the largest issue since they all cause cancer.  If you have smelt it you have been over exposed.  I know 5 or so people I have worked with at white sands test facility who have died of various types of cancer.

N2O4 is far harder to deal with as it reacts with far more material, builds up salts on surfaces, and when moisture is added forms nitric acid.  It will cause burns on skin and eyes, and if it's inhaled it can cause severe damage or death.

Offline Kosmos2001

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Re: Monomethylhydrazine Q&A
« Reply #7 on: 02/20/2017 02:35 PM »
[]

Welcome to NSF and thanks for your answer.  ;)

Offline StvB

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Re: Monomethylhydrazine Q&A
« Reply #8 on: 08/22/2017 12:08 PM »
Instead of posting a new Q&A, hopefully I can get this thread going again and ask my questions here.

In reading about hypergolic engines, I've noticed that the west generally uses MMH and the east uses UDMH. Is this a valid/true observation? If it is true, why is that the case? Did each region/country have the industry and infrastructure set up for one and therefore tend to use that hypergolic fuel? How different are MMH and UDMH?
-Steve

Offline Jim

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Re: Monomethylhydrazine Q&A
« Reply #9 on: 08/22/2017 01:29 PM »
CH3(NH)NH2 vs H2NN(CH3)2

One vs two CH3 Methyls

More ISP vs more stability
« Last Edit: 08/22/2017 01:33 PM by Jim »

Offline StvB

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Re: Monomethylhydrazine Q&A
« Reply #10 on: 08/22/2017 05:04 PM »
CH3(NH)NH2 vs H2NN(CH3)2

One vs two CH3 Methyls

More ISP vs more stability

Does it hold true that former Soviet and derivative engines primarily use UDMH and their American counterparts use MMH? If so, is there an explanation as to why that is the case? Or is it because they went in different directions, one seeking more Isp and the other a more stable prop?
« Last Edit: 08/22/2017 05:05 PM by StvB »
-Steve

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