For Questions That Don't Merit Their Own Thread

[p1t1o]

5 hours ago, 0111narwhalz said:

What chemical system has the highest specific energy? Does it also rank highly on energy density? What is its specific energy, abd how quickly does it release this energy?

There are many candidates, but you'd need a table of exact figures to get the one-right-answer. One thing to note, that in the grand scheme of things, chemical energy density is not particularly high. Pretty much any nuclear reaction beats them by an order of magnitude or few. Things at the top of the list tend to be advanced explosives and dont necessarily make great rocket fuels, if that is what you getting at.

There are some figures here:

https://en.wikipedia.org/wiki/Energy_density_Extended_Reference_Table

Note the difference between metallic hydrogen (as used as a rocket fuel) and that which we can get from natural uranium in conventional reactors!

[Alpha_Mike_741]

Four questions :

1) Mass of falcon 9's payload fairings (One side) . Spaceflight101 says ~1.750 tons. is it both sides or just one?

2)Approximate power of F9 first stage cold gas thrusters (individually)

3)Any info on the fluid used in fin hydraulics and fin hydraulics in general . is it RP-1 Pressurized by helium?

4) (I know , i know) How much helium is used for lowering the legs ? Each leg weighs about 525 kg according to Spaceflight101

[Kerbal01]

14 minutes ago, Alpha_Mike_741 said:

Four questions :

1) Mass of falcon 9's payload fairings (One side) . Spaceflight101 says ~1.750 tons. is it both sides or just one?

2)Approximate power of F9 first stage cold gas thrusters (individually)

3)Any info on the fluid used in fin hydraulics and fin hydraulics in general . is it RP-1 Pressurized by helium?

4) (I know , i know) How much helium is used for lowering the legs ? Each leg weighs about 525 kg according to Spaceflight101

3: it is indeed RP-1 as the hydraulic fluid.

[Alpha_Mike_741]

Just now, DarthVader said:

3: it is indeed RP-1 as the hydraulic fluid.

I'm a total newbie in this topic so don't mind me much but , is there a way to have a very rough approximation of the helium weight/mass used for fin hydraulics? and for leg deployment?

 

Edited March 15, 2017 by Alpha_Mike_741

[Kerbal01]

6 hours ago, Alpha_Mike_741 said:

I'm a total newbie in this topic so don't mind me much but , is there a way to have a very rough approximation of the helium weight/mass used for fin hydraulics? and for leg deployment?

 

Thats likely proprietary 

[munlander1]

If you had an object in a perfect vacuum and the object held a ststic charge, would it lose its charge.

[0111narwhalz]

If it is in a closed system (vacuum with no neighbors), charge must be conserved. The object will retain its charge, although depending on the object it might not retain its "object-ness" and fly apart. But the shrapnel would still have the charge.

[p1t1o]

If its a negative charge above a certain level, I'd imagine that in a vacuum you'd shed an electron or several, reducing the charge held.

Im not sure, anyone disagree?

Edited March 17, 2017 by p1t1o

[0111narwhalz]

5 hours ago, p1t1o said:

If its a negative charge above a certain level, I'd imagine that in a vacuum you'd shed an electron or several, reducing the charge held.

Im not sure, anyone disagree?

Well, if you consider the electrons to be a part of the object, then the object has only fragmented. If you consider the object the sum of its fragments, then the object still retains its charge.

[Alpha_Mike_741]

According to this article from Wikipedia about ISS SAWs , can i assume that each of the blankets (in a SAW) approximately generates 16.4 KW of power? Need it for making configs so doesn't have to be 100% accurate.

Edited March 20, 2017 by Alpha_Mike_741

[0111narwhalz]

What is the enthalpy change of WD-40 burning in liquid oxygen, and what is the specific heat of its products? I want to know if one could build a rocket out of WD-40 and duct tape.

[p1t1o]

9 hours ago, 0111narwhalz said:

What is the enthalpy change of WD-40 burning in liquid oxygen, and what is the specific heat of its products? I want to know if one could build a rocket out of WD-40 and duct tape.

You're gonna need a breakdown of the composition of WD-40 - I presume it is a specific blend of various light hydrocarbons.

If you can find literature values for kerosene in LOx, those would be a pretty decent approximation. Unless WD-40 has some funky functional groups in it, the energy contained in its bonds should be largely similar, since they are all C-C and C-H bonds and the combustion products, if completely reacted, will be the same too - mostly CO2 and H2O.

Of course if there are some unusual compounds in WD-40 (like say cyclic groups, nitrogens, alcohols etc), that could widen the difference between it and kerosene.

[paulprogart]

15 minutes ago, p1t1o said:

You're gonna need a breakdown of the composition of WD-40 - I presume it is a specific blend of various light hydrocarbons.

The fomula is proprietary, but Wired went and did a spectrographic analysis some years ago:

https://web.archive.org/web/20140119014037/http://www.wired.com/science/discoveries/magazine/17-05/st_whatsinside

Heavier stuff than I thought it'd be.

[Wjolcz]

Will JWST really be on the Lagrange point for the cooling purposes? I've heard people say it's because of Earth's shadow, but to me it doesn't make much sense since Earth will simply be too far away to cover the Sun in any meaningful way. To me it seems obvious it will be there to have direct line of sight with DSN all the time and more observation time than there would be in LEO (since Earth would get in the way half of the time). Maybe it's the light and heat bounced back by Earth's clouds that would make JWST unusable in LEO?

Edited March 21, 2017 by Veeltch

[p1t1o]

18 minutes ago, paulprogart said:

The fomula is proprietary, but Wired went and did a spectrographic analysis some years ago:

https://web.archive.org/web/20140119014037/http://www.wired.com/science/discoveries/magazine/17-05/st_whatsinside

Heavier stuff than I thought it'd be.

Yeah, there's a few of the less "plain" molecules in there, the mineral oil is going to be an unholy mix of god knows what too. But its seems likely that it is mostly the straight-chain hydrocarbons.

Wouldn't it be easier just to use kerosene (or gasoline, or some other more easily characterised hydrocarbon) in the first place?

 

[Green Baron]

1 hour ago, Veeltch said:

Will JWST really be on the Lagrange point for the cooling purposes? I've heard people say it's because of Earth's shadow, but to me it doesn't make much sense since Earth will simply be too far away to cover the Sun in any meaningful way. To me it seems obvious it will be there to have direct line of sight with DSN all the time and more observation time than there would be in LEO (since Earth would get in the way half of the time). Maybe it's the light and heat bounced back by Earth's clouds that would make JWST unusable in LEO?

Yes, JWST is planned for L2. The heat shield doesn't need adjustment like it would be necessary in LEO where angles of incoming heat from sun, earth and moon change rapidly while orbiting.

It's just a quiet place, there isn't that much traffic (yet) :-) Also keeping it in an orbit around L2 requires only very little dV over the whole mission time (a few 100m/s). And it has a free view on most of the sky over the course of a year.

In L2 it is practically in orbit around the sun.

See: https://jwst.nasa.gov/orbit.html

Edited March 21, 2017 by Green Baron

[0111narwhalz]

12 hours ago, p1t1o said:

Wouldn't it be easier just to use kerosene (or gasoline, or some other more easily characterised hydrocarbon) in the first place?

Yeah, but then I wouldn't be able to make the Kerbal Engineering Flowchart and the Regular Engineering Flowchart the same. I want to add WD-40 if it's not moving, whether or not that's because something's stuck or because I don't have the delta-v.

Could I just burn a known mass of WD-40 in a bomb calorimeter and measure the difference of heat? That would circumvent the whole "proprietary composition" thing and give me the numbers that are relevant straight off.

[p1t1o]

10 hours ago, 0111narwhalz said:

Could I just burn a known mass of WD-40 in a bomb calorimeter and measure the difference of heat? That would circumvent the whole "proprietary composition" thing and give me the numbers that are relevant straight off.

Well yeah, that is exactly how you'd empirically determine the answer lol

 

[shynung]

For the actual chemists in this forum.

Are common automobile gasoline suitable for engine regenerative cooling? I'm talking about piston engines, not rocket combustion chambers.

[p1t1o]

1 hour ago, shynung said:

For the actual chemists in this forum.

Are common automobile gasoline suitable for engine regenerative cooling? I'm talking about piston engines, not rocket combustion chambers.

More of an engineering question than a chemistry one - Im not entirely certain of the answer but came across this:

http://pstu.ru/files/file/2015/conf/zhenjian_jia_weixing_zhou_wenchao_liu_research_on_effects_of_fuel_pyrolysis_to_performance_of_internal_combustion_engine.pdf

Looks like it might be a "yes", theoretically.

 

Edited March 22, 2017 by p1t1o

[sevenperforce]

Is the limiting factor in deep-throttling a pump-driven liquid-fueled rocket engine the pump, the chamber, or the nozzle? Or does it vary from system to system?

For example, Raptor can downthrottle to 40% of max rated thrust. Does the 40% minimum have to do with combustion instability in the chamber, or flow choking in the nozzle, or flow within the turbopump and preburner?

[kunok]

On 22/3/2017 at 4:55 PM, sevenperforce said:

Is the limiting factor in deep-throttling a pump-driven liquid-fueled rocket engine the pump, the chamber, or the nozzle? Or does it vary from system to system?

For example, Raptor can downthrottle to 40% of max rated thrust. Does the 40% minimum have to do with combustion instability in the chamber, or flow choking in the nozzle, or flow within the turbopump and preburner?

First, raptor still doesn't exist yet, so any characteristic of it isn't real.

What you are asking is very very complex, but IIRC the most determinant one given a nozzle was the injector type, how good it mixes and spreads both the oxidant and the fuel. My propulsion teacher was a specialist in solid rockets tho, so I may be wrong.

On 22/3/2017 at 1:58 PM, shynung said:

Are common automobile gasoline suitable for engine regenerative cooling? I'm talking about piston engines, not rocket combustion chambers.

That's an engineering question, and yes is already done to some extent, next to the inlet valve you have some regenerative cooling, even if you don't want to. Remember that the mayor focus in automotive industry is to cut cost, to ridiculous extents, this would be very expensive to do properly.

[DerekL1963]

On 3/22/2017 at 8:55 AM, sevenperforce said:

Does the 40% minimum have to do with combustion instability in the chamber, or flow choking in the nozzle, or flow within the turbopump and preburner?

Yes.

[sevenperforce]

4 hours ago, DerekL1963 said:

Yes.

Heh.

But, all other things being equal, which elements are typically the most sensitive to throttle rates? For example, let us say that a given staged-combustion engine can throttle down to 20% of its max stated thrust. What would fail first below that throttle setting?       

[DerekL1963]

On 3/23/2017 at 7:15 PM, sevenperforce said:

Heh.

But, all other things being equal, which elements are typically the most sensitive to throttle rates? For example, let us say that a given staged-combustion engine can throttle down to 20% of its max stated thrust. What would fail first below that throttle setting?       

I don't know enough to say for certain...  especially since there are so many feedback loops!