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For SpaceNut ... we did not have a topic about Hydrazine...
kbd512 reminded us recently of the advantage of using hydrazine for a Mars expedition..;l.
The book and movie "The Martian" assumed hydrazine as the propellant for the landed vessel.
In light of the risks of using hydrazine, I asked Google. It found a number of discussion.... this one is from Space Stack Exchange
Hydrazine, as for small monopropellant thrusters, has been in use for decades on hundreds of satellites. One model the "1N Monopropellant Hydrazine Thruster" is claimed to be in use in 165 units. Other models have similar deployment records.
Reference: space-propulsion.com.
Many studies of monopropellants were done during the 60s and 70s. A book by: Belal, Hatem -- 2009/05/26SP Modeling of Hydrazine Decomposition for Monopropellant Thrusters presents a summary performance table of a few monopropellants, including hydrazine and N2O
. I am attempting to paste in a summary table. Here it goes:enter image description here
Hydrazine has higher Isp but N2O
has higher combustion temp likely needing more exotic materials.Overall, hydrazine has such a built-in infrastructure, long-term installed performance base that it unlikely that it would be displaced.
The toxicity, carcinogenic properties, corrosiveness, etc. of hydrazine are greatly overstated from my experience. I was working in the 60s in a small combustion research company. In one work area studies of hypergolic ignition parameters of N2O4
and hydrazine, UDMH, Aerozine 50, etc. were done. High speed movies and temperature and gas composition measurements were done to support the testing. I lived in clouds of hydrazine and N2O4
fumes. N2O4
was treated with respect. Hydrazine was not treated with much concern. Hydrazine has an ammonia odor and it was attempted to keep that as low as possible but there were no real safety limits. Also, there were no easy measurement instruments for ambient concentrations. No one in our group has become ill from anything the could have been related to hydrazine and N2O4
. Likely this work could not be done today especially in a suburban industrial park.In its document EPA estimates that, if an individual were to continuously breathe air containing hydrazine at an average of 0.0002µg/m3
(2.0∗10−7mg/m3
) over his or her entire lifetime, that person would theoretically have no more than a one-in-a-million increased chance of developing cancer as a direct result of breathing air containing this chemical.I think hydrazine will be used for a long time.
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This post is reserved for an index to posts that may be contributed by NewMars members over time.
The issue that will be debated is risk. Hydrazine clearly has significant advantages. The risks involved in it's use are also significant.
In my opinion, it is up to the organization to determine how much risk it is willing to take with humans it has invited to fly on it's behalf.
SpaceX is reported to use hydrazine for it's Draco thrusters. Decontamination procedures are followed when SpaceX capsules land.
This topic would appear to have room for considerable discussion, since each NewMars member has a different risk tolerance. Risk tolerance tends to be higher when the risk taker is not riding the vehicle in question.
Update: There would appear to be a significant business opportunity for an entrepreneur able to set up a fuel depot on Phobos (for example). If hydrazine is the fule of choice for flights to the surface and return, then there should be a substantial market opportunity.
I wonder how badly the surface of Mars would be contaminated by hydrazine landing and launch operations.
Index:
GW Johnson on risk, including the greater toxicity of the oxidizer:
https://newmars.com/forums/post.php?tid … qid=231688
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All the hydrazines are similar in toxicity, and very similar to the toxicity of anhydrous ammonia, such as what farmers put on their fields. Even the decontamination is similar: heavy dilution with water, while wearing protective gear to keep the alkaline corrosive off your skin, and while breathing with a self-contained air or oxygen supply.
It's the NTO oxidizer used with any of the hydrazines that is truly dangerous. The toxicity rating is far higher, because even a whiff of it causes lung damage that cannot be treated. You will die from it, just slowly. That requires a fully-sealed suit that is essentially a pressure suit, with a self-contained air or oxygen supply. Ordinary protective clothing is not adequate. You must have the sealed suit.
You need the oxidizer because monopropellant Isp with hydrazine decomposition is far lower Isp. It's down near 200 sec, when hydrazine-NTO Isp is up near 300-330 sec.
GW
Last edited by GW Johnson (2025-05-15 23:39:18)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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