27

Chemical rockets will never have more than 600 seconds specific impulse. Storing free radicals in propellant to defeat this limit is impractical. Validated. Chemical rockets in use top out at 450-460 seconds, with a demonstrated test-stand record of 542 seconds. ~500km range rockets will use chlorine pentafluoride and a hydrazine derivative. As far as I ...


22

LMP-103S and hydrazine differ in more ways than that hydrazine unlike LMP-103S is highly toxic and carcinogenic and that LMP-103S has higher performance. LMP-103S requires more catalyst heating to burn and the burning temperature (about 1600 C) is considerably higher than for hydrazine (about 800 C). The propulsion system and thus also the on-board ...


6

Our company (Malin Space Science Systems) is collaborating with Stellar Explorations to develop a very small biprop propulsion system for cubesat missions. There is a definite lack of options in this size range, mostly because cubesats have been prohibited from having significant propulsion systems by launch providers or primary launch customer rules up ...


6

The thrust-to-weight ratio is going to vary greatly for small thrusters (and hydrazine monoprops are generally quite small), with the very smallest having much lower thrust-to-weight ratios; mass doesn't scale down linearly with thrust at the low end. For example, Airbus makes 1N, 20N, and 400N hydrazine thrusters, all pressure fed with similar operating ...


5

New Horizons used its monopropellant attitude control thrusters for course correction. Because it couldn't make large course changes with the limited fuel available, the choice of targets was severely constrained: Mission planners searched for one or more additional Kuiper belt objects (KBOs) of the order of 50–100 km (31–62 mi) in diameter as targets for ...


5

Specific heat, also known as heat capacity, in J/kg K (Joules per kilogram per Kelvin). Water, of all liquids, has the highest specific heat; ammonia and hydrazine have much lower specific heats. Also, most metals don't react with gaseous hydrazine, it being an oxygen slurper. The chapter "Conclusions and Recommendations", p. 24 sqq of this document, ...


4

I'm the SkySat propulsion lead and have been flying LMP-103S since June 2016 when SkySat-3 launched from India. To answer the question: Yes it is viable and has a number of advantages, mostly the (Isp * density) is much better than hydrazine. But, right now the engines are more expensive to build than those running hydrazine (due to higher combustion ...


3

Yes, the fuel would be used as a monopropellant because as soon as you excite the metallic hydrogen, it will be just H molecules which will quickly bond to each other to Form H2, creating mass amounts of energy. If you convert it back to molecular hydrogen, all the energy required to produce it is released. No burning would be necessary, it would just be the ...


3

From the ECAPS page on LMP-103S performance... The specific impulse is ≥ 6% higher and the propellant density is 24% higher. As a result, the satellite can either be fitted with a smaller tank, or the mission duration can be extended while retaining the same tank size. Volume is important because you only have so much room inside a payload fairing. ...


3

I've been unable to find any other reference to the quote in your question, that HAN can be "Allowed to freeze". I suspect what the asker meant was that the satellite could be allowed to operate in colder conditions. Looking at the MSDS on HAN, at -80 degrees celsius, the fuel doesn't freeze in the traditional sense but forms an amorphous glass. Hydrazine ...


3

A nuclear heating device with a mass of around 1000kg wouldn't make a measurable difference on the martian atmosphere in it's total (nuclear) lifetime. If you use MMRTG's, the same power source that the Curiosity rover and the Voyager probes have, you could bring around 20 of them as they mass around 50 kg a piece. Your average MMRTG puts out 125 Watts of ...


3

In answer to "what's taking so long", LMP-103S has actually made steady progress since that time, but the space industry is very conservative, so change takes time. One issue a friend of mine in the field mentioned that may potentially be slowing things down is that LMP-103S apparently currently costs about $5000/kg (about 15x the cost of hydrazine).


3

My reading of the Aviation Week article on this seemed to suggest that while Landsat-7 was not designed to be refueled, when they looked at its design, they found a fuel line, they could patch into that could be used to fill the tanks again. They need to cut away the insulation to get to the pipe, and then will probably use some variant of a vampire tap to ...


2

Well, the density of hydrazine is $1.021 \frac{kg}{L}$, and its $I_{sp}$ is $220 s$ as a mono propellant. (Both values from the Wiki page). That is a total of $224.6 \frac{kg \cdot s}{L}$, using the same units as your source.


2

Otto fuel II has a specific impulse of 200 s, which is really low compared to solids at ~250 s, hypergolics at ~250 s and RP-1/LOX at 300 s.


2

When would the density Isp product be an important performance metric of a propellant? It's always important. Specific impulse is a measure of impulse provided per mass unit of combusted propellant, which is a great metric for fuel-efficency in a rocket. However, it doesn't take into account the mass of things other than fuel -- like fuel tankage, which ...


1

Oh, I see. Let's say I am building an ambitious 3U cubesat and I've allocated 1U for fuel and 2U for payload and bus, and I want to select the propellant that will give me the most delta-v. I don't know Cubesat mass density (kg/U) statistics? but lets say I've got a 3 kg (dry mass $m_D$) 3U cubesat with a 1 liter tank. What is the delta-v as a function of $...


1

With the exception of ion propulsion, all major maneuvers from spacecraft are done with either monopropellants, with a few exceptions, most notably the bipropellant dinitrogen tetroxide, used by the Apollo program, and a few other similar missions. The exceptions are all crewed vehicles, where masses are typically much larger. Monopropellants are easier to ...


1

I think LMP - 103 is Liquid Mono propellant which is a green monopropellant which is ionic salt liquid higher density than commercial hydrazine propellant. It is less toxic and high performance than hydrazine. LMP 103 is a Ammonium Di Nitramide (ADN) based monopropellant with water and fuel component can be used as better replacement for highly toxic ...


1

It was reportedly used in Planet's SkySats launched by the first Minotaur C; see Space.com's Orbital ATK's 'Frankenstein' Minotaur C Rocket Blasts Off on Halloween.


Only top voted, non community-wiki answers of a minimum length are eligible