Extra Pipes...

[Matuchkin]

So, it's fairly easy to visualise the structure of the components of a rocket engine (i.e. the turbopump, the valves, the nozzle, the gimbal, etc). But when you think you have most of this figured out, you look at a real-life engine of that sort and see this:

I mean, you can see the main structures; turbofan, main fuel pipes, cooling sys- whatever, it's all there, but what are these extra pipes about?

The computer model/diagram of the above RD-180 displays a neat system with all of its components. Then you stare at the real-life photo of that engine and all your self-esteem just collapses. Take another look:

Same case here. I can see everything that's going on in the Klimov VK1 diagram above, but the actual image displays so much more than that.

So what's with these pipes? Are they there to spread coolant across every component of the engine? Are they there as systems unrelated to the engine that just happened to be stuffed into the engine fairing? Are they for spreading the fluids in a more efficient way? Hydraulics? Electric cables? What are these thousands of extra tiny pipes and valves all about, and what systems do they belong to?

Edited November 22, 2017 by Matuchkin

[regex]

Hydraulics, coolant, lubrication, additional feeds for different chemicals than your fuel and oxidizer, trim lines for ratios, redundant systems (maybe), allocation lines, etc... You're generally going to ditch a rocket engine after launch so everything is vital and needed.

Edited November 22, 2017 by regex

[PB666]

Those are because of the turbocharger, I believe

So in kerbal you have a rocket motor that generates force and sometimes electricity (though not all rockets generate electricity) and some have the ability to be started several times.

 

We could draw out an SSME, one of the most complicated rocket engines ever to be built, or basically simplify the model. So here goes

Oxidizer
Reductant
Control

Step 1 pressurize the tanks
1. Reductant tank pressurization
2. Oxidizer tank pressurization

Step 2  Heat the reductant if neccesary

Step 3 Mix some rated oxidant and all rated reductant together

Step 4 ignite

Step 5 pass over turbocharger turbines
1. Reactor/turbocharger assembly has a shaft
a. the shaft breaches the assembly at both ends
b. at one end there may be a generator
c. it could also be tied into fuel circulation . . . .

Step 6 feed the partially burnt mixture into the main engine combustion chamber with the rest of rated O2

Step 7 using a gated bleed off run some of the fuel over a generator (if not done in step 5).

There may be a variety of needs for control. So lets see if we can figure out the piping.

Electrical
1. For any rocket that has a generator you have wires. The engines get very hot so the wires need to be protect from the heat of the engine.
2. For any rocket that can be throttled you have wires to control the throttling mechanism.
3. For any rocket that can be restarted multiple time you have a reignition wiring. (remember that a resting fuel in space/micro gravity has no shape in a tank, so that the fuel may have to be staged long enough to generate momentum of the fuel)
4. All rockets should have some sort of mechanism for shutting down when one of the fuels is found to be empty.
5. Every valve needs some sort of actuator mechanism

Hydrolic. The hydrolic fluid pump either needs to be run by the electrical system or off the turbocharger

Control. Turbopumps create pressures and the pressures need to be controlled and governed during flight, this can be done by forking the pressure down a regulatory line to another part of the pump, engine or other pump.
Some of these pressures could be fed though the turbopump but it may be easier if you have multiport (just like on a car were the vacuum lines are piped off a bus to various parts of the engine) just to use one of the outlets and a pipe, then all you have to do is drill a hole, thread the hole, screw in an inlet connector and run a high pressure aluminum line (such as the type used for power steering pump on a car).

There may be various needs for lubricant. At the core of the lubrication is the turbocharger (turbopump). The turbocharger is in a very 'corrosive' environment. At the end of the turbocharger there is a bearing, the bearing needs to be kept cool (below the seizing temperature) and lubricated (just like the valve stem in a cars engine).

http://www.k-makris.gr/RocketTechnology/TurboPumps/turbopumps_for_liquid_rocket_eng.htm

When the turbocharger preburner outlet pressure and appropriate oxygen added exceed the oxygen inlet pressure, then an oxygen turbopump needs to be added otherwise the engine will be oxygen starved and thrust will be lost. To deal with this situation a separate turbo pump needs to be added, and this may require precise regulation between the turbochargers for the reductant and for the oxidant. I should point out that SSME has both low pressure and high pressure turbopumps for each fuel.

" If water were pumped through the SSMEs instead of fuel, the three engines could drain an average family-sized swimming pool in 25 seconds. "- https://californiasciencecenter.org/exhibits/air-space/space-shuttle-endeavour/space-shuttle-main-engine-ssme

https://airandspace.si.edu/collection-objects/engine-rocket-space-shuttle-main-ssme  notice how the tubing is focused on the turbopumps. Going from one part of the turbo pump to the other.

Edit: I should point out that you can have a light weight engine like the RL10b-2 that gets 465.2 ISP using hydrolox. Notice that the RL10 does not have all the fancy tubing.

So the maximum diameter of the outlet is 2.13 meters (A=3.56 meters) and has a 110 kn. (30,780 N per meter squared). The engine has a low weight but has a thrust to weight ratio of 40:1

The SSME has a lower ISP (452, some power lost in the charging) but look at the difference in thrust 2,279 kN over 2.4 meters (A = 4.52; 504,000 N per meter squared). All though the lines and turbopumps add considerably to the weight (RL10B-2 weighs 266 kg and the SSME weighs 3500 kg) but produces a higher, 53.79, TWR. This all comes from the complicated turbo-pumping systems

Even if the engine had a lower ISP for hydrolox fuels these are still desirable engines to have, its really the demands of gaining 7400 m/s of horizontal velocity in a few hundred seconds requires an engine that can haul out the thrust.

 

 

Edited November 22, 2017 by PB666

[kerbiloid]

Every engine contains at least one excessive detail.
You can easily ensure, trying to rip it apart and then assemble it back.

Edited November 22, 2017 by kerbiloid

[StrandedonEarth]

39 minutes ago, kerbiloid said:

Every engine contains at least one excessive detail.
You can easily ensure, trying to rip it apart and then assemble it back.

And any parts left over after that you obviously didn’t need...

[magnemoe]

36 minutes ago, StrandedonEarth said:

And any parts left over after that you obviously didn’t need...

Its an story about an guy who repaired his outboard motor, then assembling it he found one part he did not find any place to place nor did testing show any need for it so he skipped it.
Initial testing worked well, so he went fishing, after some hours he stopped at an islet to take an dump, trowing the motor in reverse did nothing, that is outside of locking the engine in neutral. 
He just found the purpose of the missing part who was left back in his garage. He was rescued by another boat the next day
(note this is pretty much an urban legend and probably not very true)

Edited November 22, 2017 by magnemoe

[PB666]

You have to remember that SSME and like engines have many sensors on the motor and the fuel pressurization system that can be used to discontinue flight progression.

https://en.wikipedia.org/wiki/Space_Shuttle_main_engine#Incidents

These are not outboard motors, you can get a tow back into port if you run out of fuel before reaching orbit.

 

Edited November 22, 2017 by PB666

[Nuke]

its sort of the same reason why modern computer power supplies have so many damn wires. most of them are carrying the same voltage levels on very few rails and a lot of grounds that all seem to go to the same place. and you start to wonder why they just didn't use one bigger wire per voltage instead of a bunch of little ones. of course its all about load balancing and isolation, either one would make turn your computer into a doorstop if they weren't done up that way. id love for the electrical engineers who design this stuff to come up with better solutions so i dont have to pull my hair out trying to get all my wires into my mini itx case.

[PB666]

3 hours ago, Nuke said:

its sort of the same reason why modern computer power supplies have so many damn wires. most of them are carrying the same voltage levels on very few rails and a lot of grounds that all seem to go to the same place. and you start to wonder why they just didn't use one bigger wire per voltage instead of a bunch of little ones. of course its all about load balancing and isolation, either one would make turn your computer into a doorstop if they weren't done up that way. id love for the electrical engineers who design this stuff to come up with better solutions so i dont have to pull my hair out trying to get all my wires into my mini itx case.

Alot of those wires exist for legacy reasons. POwerSpec sells a PSU that has modularized cables, you can select the ones you don't want to use. Although the last power supply I bought from them failed the system board 5V sleep voltage and was exchanged (talk about a sorry arsed reason for not working) .. . .I open all the panels on the case and stuff the unused cables behind a infrequently opened panel. If you are good at electrical you can cut them and wire nut them. Its annoying though cause you never know when you might need an old legacy connection. Its kind of like RS232 (been around since like 1960) on the mobo, you almost never need the connection, but when you do it really sucks not to have it.

 

[YNM]

I guess some of them are extra structural components or stemming from the chamber walls itself, some are cables, some are smaller pipes for instrument reading. Much like how your home have furnitures and the roads have markings, lightpoles, signage and other equipments alongside. They're not the main thing, but they helps in operating it. The smaller components aren't depicted to learn how they work of course, no one could be arsed enough to draw all the cables and pipes, they usually comes separately. It also reflects how they're manufactured - make the big things first then put the rest in or around.

Edited November 23, 2017 by YNM

[Nuke]

17 hours ago, PB666 said:

Alot of those wires exist for legacy reasons. POwerSpec sells a PSU that has modularized cables, you can select the ones you don't want to use. Although the last power supply I bought from them failed the system board 5V sleep voltage and was exchanged (talk about a sorry arsed reason for not working) .. . .I open all the panels on the case and stuff the unused cables behind a infrequently opened panel. If you are good at electrical you can cut them and wire nut them. Its annoying though cause you never know when you might need an old legacy connection. Its kind of like RS232 (been around since like 1960) on the mobo, you almost never need the connection, but when you do it really sucks not to have it.

 

if i was really desperate id get my crimpers out and get some molex pins off ebay. the modular housings can just be salvaged from scrap. modular power supplies are nice but they never really help much. i havent had one where i didnt have to connect most of the cables because one doesnt reach. im actually using a modular sfx power supply now. my case doesnt support it but adapter plates are available for that. its tiny compared to a massive atx supply. its freed up more space for drives and cables and its modular too. i think atx supplies are getting bigger because i couldnt find one that would fit in my case when i upgraded my video card a couple months ago.