6 ms·

In the steam days, it was a major operation to adjust the output of an engine. Valve linkages had immediate effect on the output, but you also had to adjust the

by tlb 9y ago

In the steam days, it was a major operation to adjust the output of an engine. Valve linkages had immediate effect on the output, but you also had to adjust the boiler heat input to keep the temperature within limits. Far enough back, there were men shoveling coal into the boilers who had to be told to slow down or speed up. Do you think it's mainly bureaucratic inertia that keeps it separate? Or is there something more complicated about controlling engine power than I imagine?

chrisseaton 9y ago
> Valve linkages had immediate effect on the output, but you also had to adjust the boiler heat input to keep the temperature within limits. Can you not vent some of the steam, so the same volume of steam is being produced and the temperature the same but only some of it goes to the drive?
- a_t48 9y ago
  This would mean wasting fuel, no?
  - chrisseaton 9y ago
    What's that got to do with anything? The comment was about the ability to vary power at all, not doing it efficiently. Are you going to choose to crash into something because it's wasting fuel to vent part of the steam?
    - femto 9y ago
      A basic of driving a steam engine is not to waste steam, since steam represents fuel, which in turn represents money. As you say, not having an accident is more important than wasting a bit of fuel (hence safety valves on steam boilers), but in everyday operation wasting fuel is a cardinal sin and something that is to be avoided. At one point I was involved in steam rail preservation, and the old-timers used to mourn the loss of engine driving/firing skills whenever engines sat at the platform with the safety valves blowing. The ship command structure was a form of information hiding, whereby the commander only worried about the speed, whilst the engineer worried about how to efficiently deliver the requested speed.
    - masklinn 9y ago
      > Are you going to choose to crash into something because it's wasting fuel to vent part of the steam? Under emergency you will vent, but under normal operations where you just want to slow down you care very much about efficiency. Not just for monetary reasons either (though that's a factor) but because the lumps of coal you're not burning now could save your ass in bad weather and make you reach safety instead of being stranded in the middle of the ocean.
    - killjoywashere 9y ago
      At sea, efficiency gets you back to land.
  - laneuffer 9y ago
    It is wasting fuel, I think?
- okabat 9y ago
  I think their point is that when changing engine output is labor-intensive, it made perfect sense to have an officer giving orders and somebody else implementing them. Why the command structure hasn't shifted to accommodate modern technology is an interesting question
  - diggernet 9y ago
    It's not labor-intensive, it's attention-intensive. You want the person managing the speed to be focused on that. You want the person managing the heading to be focused on that. And you definitely don't want the officer to be distracted by maintaining course and speed when they need to be keeping track of what's going on around the ship.
    - deleted 9y ago
      [deleted]
    - PeterisP 9y ago
      You want the person managing the speed to be focused on that if managing speed is still inherently and unavoidably attention-intensive - if modern control technology is able to automagically maintain speed at x knots, adjusting all the various engine control parameters to implement that, then an extra person in the loop only means an extra chance for mistakes or delays.
      - cocoablazing 9y ago
        If the military learned a lesson from exploding a reactor with an automatic control system, you might never know - it's not required to be reported to the public.
        josefx 9y ago
        If an automatic control system can blow up a reactor so can the manual one. You have a problematic design issue in both cases. You can also still assign someone to keep an eye on the reactor in case things go bad an have that person pull an emergency stop or warn the guy in charge. There is no reason to relay every little speed change through several people.
- schlock509 9y ago
  I think if the same volume of steam is being produced then it's going to cause problems regardless
toomanybeersies 9y ago
On a nuclear powered ship, yes, since you still essentially have a steam engine, the engine telegraph (throttle) isn't actually linked directly to the engine. On a modern diesel or gas turbine ship, no there's not. Obviously there are limits to what the engine can do still.
- misnome 9y ago
  The nuclear part isn’t just used to generate electricity for the motors?
  - Marazan 9y ago
    The nuclear power plant is heating water to generate steam.
    - pbhjpbhj 9y ago
      Which presumably drives a turbine to make electric which can run motors, charge batteries, run scrubbers, run heaters, etc., presumably. They're not direct driving the screw with steam power from the reactor heat-exchange, surely.
      - avar 9y ago
        It's hard to find anything like a schematic of a Nimitz-class carrier for obvious reasons, but as far as I can tell yes, it's all directly steam powered. The reactor boils (sea)water, which is used to power 4 steam turbines[1][2][3], those turbines drive the propellers. You've probably seen aircraft carrier decks covered in smoke. This is because the Nimitz's catapult system is directly steam powered, service steam is widely used on the class. I can't find a citation for this now (this is from memory) but I saw some documentary on it once where it was mentioned in passing that even the washing machines on the ship were steam powered. There's service steam everywhere on the Nimitz. Having steam power everywhere introduces a lot of complexities, which is why the Navy's moving away from it with their new carrier class[4]. The Gerald R. Ford-class does away with service steam in favor of more powerful electric generators. There'll be no service steam, just steam to drive the electric turbines. 1. http://www.nimitz.navy.mil/FACTS.html http://www.nimitz.navy.mil/FACTS.html 2. https://en.wikipedia.org/wiki/Nimitz-class_aircraft_carrier#Propulsion https://en.wikipedia.org/wiki/Nimitz-class_aircraft_carrier#... 3. https://www.marinelink.com/news/dresserrand-propulsion302604 https://www.marinelink.com/news/dresserrand-propulsion302604 4. https://en.wikipedia.org/wiki/Gerald_R._Ford-class_aircraft_carrier https://en.wikipedia.org/wiki/Gerald_R._Ford-class_aircraft_...
cocoablazing 9y ago
Yes, steam demand controls the power response of a nuclear reactor.
jasonwatkinspdx 9y ago
> Or is there something more complicated about controlling engine power than I imagine? Large marine diesels such as used by container ships do need to follow a procedure to change out of the cruise rpm. I don't know how much that can be skipped/abbreviated in case of an impending collision, but I do know that generally it takes more than just someone on the bridge changing a control setting.

by tlb 9y ago

chrisseaton 9y ago

> Valve linkages had immediate effect on the output, but you also had to adjust the boiler heat input to keep the temperature within limits. Can you not vent some of the steam, so the same volume of steam is being produced and the temperature the same but only some of it goes to the drive?

a_t48 9y ago
This would mean wasting fuel, no?
- chrisseaton 9y ago
  What's that got to do with anything? The comment was about the ability to vary power at all, not doing it efficiently. Are you going to choose to crash into something because it's wasting fuel to vent part of the steam?
  - femto 9y ago
    A basic of driving a steam engine is not to waste steam, since steam represents fuel, which in turn represents money. As you say, not having an accident is more important than wasting a bit of fuel (hence safety valves on steam boilers), but in everyday operation wasting fuel is a cardinal sin and something that is to be avoided. At one point I was involved in steam rail preservation, and the old-timers used to mourn the loss of engine driving/firing skills whenever engines sat at the platform with the safety valves blowing. The ship command structure was a form of information hiding, whereby the commander only worried about the speed, whilst the engineer worried about how to efficiently deliver the requested speed.
  - masklinn 9y ago
    > Are you going to choose to crash into something because it's wasting fuel to vent part of the steam? Under emergency you will vent, but under normal operations where you just want to slow down you care very much about efficiency. Not just for monetary reasons either (though that's a factor) but because the lumps of coal you're not burning now could save your ass in bad weather and make you reach safety instead of being stranded in the middle of the ocean.
  - killjoywashere 9y ago
    At sea, efficiency gets you back to land.
- laneuffer 9y ago
  It is wasting fuel, I think?
okabat 9y ago
I think their point is that when changing engine output is labor-intensive, it made perfect sense to have an officer giving orders and somebody else implementing them. Why the command structure hasn't shifted to accommodate modern technology is an interesting question
- diggernet 9y ago
  It's not labor-intensive, it's attention-intensive. You want the person managing the speed to be focused on that. You want the person managing the heading to be focused on that. And you definitely don't want the officer to be distracted by maintaining course and speed when they need to be keeping track of what's going on around the ship.
  - deleted 9y ago
    [deleted]
  - PeterisP 9y ago
    You want the person managing the speed to be focused on that if managing speed is still inherently and unavoidably attention-intensive - if modern control technology is able to automagically maintain speed at x knots, adjusting all the various engine control parameters to implement that, then an extra person in the loop only means an extra chance for mistakes or delays.
    - cocoablazing 9y ago
      If the military learned a lesson from exploding a reactor with an automatic control system, you might never know - it's not required to be reported to the public.
      - josefx 9y ago
        If an automatic control system can blow up a reactor so can the manual one. You have a problematic design issue in both cases. You can also still assign someone to keep an eye on the reactor in case things go bad an have that person pull an emergency stop or warn the guy in charge. There is no reason to relay every little speed change through several people.
schlock509 9y ago
I think if the same volume of steam is being produced then it's going to cause problems regardless

toomanybeersies 9y ago

On a nuclear powered ship, yes, since you still essentially have a steam engine, the engine telegraph (throttle) isn't actually linked directly to the engine. On a modern diesel or gas turbine ship, no there's not. Obviously there are limits to what the engine can do still.

misnome 9y ago
The nuclear part isn’t just used to generate electricity for the motors?
- Marazan 9y ago
  The nuclear power plant is heating water to generate steam.
  - pbhjpbhj 9y ago
    Which presumably drives a turbine to make electric which can run motors, charge batteries, run scrubbers, run heaters, etc., presumably. They're not direct driving the screw with steam power from the reactor heat-exchange, surely.
    - avar 9y ago
      It's hard to find anything like a schematic of a Nimitz-class carrier for obvious reasons, but as far as I can tell yes, it's all directly steam powered. The reactor boils (sea)water, which is used to power 4 steam turbines[1][2][3], those turbines drive the propellers. You've probably seen aircraft carrier decks covered in smoke. This is because the Nimitz's catapult system is directly steam powered, service steam is widely used on the class. I can't find a citation for this now (this is from memory) but I saw some documentary on it once where it was mentioned in passing that even the washing machines on the ship were steam powered. There's service steam everywhere on the Nimitz. Having steam power everywhere introduces a lot of complexities, which is why the Navy's moving away from it with their new carrier class[4]. The Gerald R. Ford-class does away with service steam in favor of more powerful electric generators. There'll be no service steam, just steam to drive the electric turbines. 1. http://www.nimitz.navy.mil/FACTS.html http://www.nimitz.navy.mil/FACTS.html 2. https://en.wikipedia.org/wiki/Nimitz-class_aircraft_carrier#Propulsion https://en.wikipedia.org/wiki/Nimitz-class_aircraft_carrier#... 3. https://www.marinelink.com/news/dresserrand-propulsion302604 https://www.marinelink.com/news/dresserrand-propulsion302604 4. https://en.wikipedia.org/wiki/Gerald_R._Ford-class_aircraft_carrier https://en.wikipedia.org/wiki/Gerald_R._Ford-class_aircraft_...

cocoablazing 9y ago

Yes, steam demand controls the power response of a nuclear reactor.

jasonwatkinspdx 9y ago

> Or is there something more complicated about controlling engine power than I imagine? Large marine diesels such as used by container ships do need to follow a procedure to change out of the cruise rpm. I don't know how much that can be skipped/abbreviated in case of an impending collision, but I do know that generally it takes more than just someone on the bridge changing a control setting.