4 ms·

The nuclear part isn’t just used to generate electricity for the motors?

by misnome 9y ago

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_...
    - autokad 9y ago
      some nuclear submarines are not steam powered directly, they use electric engines.
      - bzbarsky 9y ago
        Very few, if https://en.wikipedia.org/wiki/Integrated_electric_propulsion#List_of_IEP_ships https://en.wikipedia.org/wiki/Integrated_electric_propulsion... and https://en.wikipedia.org/wiki/Columbia-class_submarine#Electric_drive https://en.wikipedia.org/wiki/Columbia-class_submarine#Elect... are to be believed. The latter claims that as of 2013 there is exactly one nuclear submarine class (https://en.wikipedia.org/wiki/Triomphant-class_submarine https://en.wikipedia.org/wiki/Triomphant-class_submarine to be exact) that uses electric engines.
    - digi_owl 9y ago
      I love the way they did the electromagnetic catapult. https://en.wikipedia.org/wiki/Electromagnetic_Aircraft_Launch_System https://en.wikipedia.org/wiki/Electromagnetic_Aircraft_Launc... Basically they spin up flywheels that then dump their kinetic energy back into electric power as the catapult is released. And it allows them to finely adjust the speed of the catapult depending on the kind of aircraft they are launching.
  - jasonwatkinspdx 9y ago
    > They're not direct driving the screw with steam power from the reactor heat-exchange, surely. Yes, they are, for the simple reason that it's more efficient. This is beginning to give way to a series electrical design, but that's for reasons of increased stealth and other concerns, at the cost of overall thermodynamic efficiency. On all existing nuclear carriers steam is used for the catapults (and this is much more demanding than many people are aware of). The Ford class is developing electromagnetic catapults, which are also proving to be demanding to perfect.
deleted 9y ago
[deleted]
zwily 9y ago
The heat from the nuclear reaction in a nuclear power plant is typically just used to boil water, which turns turbines, which creates the electricity.
- LeifCarrotson 9y ago
  Does this electricity charge a battery pack, which then is used to drive the electric motors which turn the screws? This would imply that the heat generation and turbine spin-up time merely need to respond before the batteries are discharged, potentially allowing response times of minutes or hours. It would give Tesla-like instant throttle response, where the operator would move the lever and the sub would jump forward. Or does it directly power the engines? This would mean that your entire control loop would include the latency of the steam generation process. Move the lever, wait for the water to get hot, wait for the turbines to spin up, and then the screws would start to turn faster. Like the throttle response in an ancient diesel truck. Given that the original diesel submarines used giant battery arrays to power the electric motors while the engines were off, and that the former gives much better control response, I'd assume that there are still large batteries in the loop. This paper [2] supports that assertion: > The nominal cell voltage is 2.0 V. [1] The PDX-57 cell designed for Ohio-class submarines weights 2,100 pounds with a capacity of more than 10,000 Amp-hours and stored energy of 2.6 MWh. [1] The ASB-49 cell designed for the Los Angeles-class submarine weights 1,300 pounds with a capacity of 7,200 Amp-hours and stored energy of 1.8 MWh. [1] The LLL-69 type cell weights 1,500 pounds with a capacity of 8,100 Amp- hours and stored energy of 2.0 MHh. [1] A couple megawatthours is plenty to run the screws while the steam loop and nuclear reactor respond. Therefore, toomanybeersies comment: > 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. is technically correct but actually irrelevant. The nuclear reactor telegraph does control the steam turbine and eventually the battery charge, rather than the engine. But somewhere there's an electric motor controller which responds instantly. [1] http://ieeexplore.ieee.org/document/1177196/?reload=true&tp=&arnumber=1177196 http://ieeexplore.ieee.org/document/1177196/?reload=true&tp=... [2] http://large.stanford.edu/courses/2013/ph241/ditiangkin1/ http://large.stanford.edu/courses/2013/ph241/ditiangkin1/
  - 9y ago
bzbarsky 9y ago
If https://www.defensetech.org/2013/09/27/ohio-class-subs-to-shift-to-electric-drive/ https://www.defensetech.org/2013/09/27/ohio-class-subs-to-sh... is correct, then at least the Ohio class submarine drives the motor directly off the turbines, but the thing being designed to replace it will use electric motors. And actually, https://en.wikipedia.org/wiki/Columbia-class_submarine#Electric_drive https://en.wikipedia.org/wiki/Columbia-class_submarine#Elect... talks about the same, but with some comments about the few submarine types that do this so far. And following the link to https://en.wikipedia.org/wiki/Integrated_electric_propulsion https://en.wikipedia.org/wiki/Integrated_electric_propulsion gives us https://en.wikipedia.org/wiki/Integrated_electric_propulsion#List_of_IEP_ships https://en.wikipedia.org/wiki/Integrated_electric_propulsion... Looks like some of the most modern or in-design classes are using electric drive, but most things out there are using direct mechanical linkage to the turbines to drive the propeller.

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_...
  - autokad 9y ago
    some nuclear submarines are not steam powered directly, they use electric engines.
    - bzbarsky 9y ago
      Very few, if https://en.wikipedia.org/wiki/Integrated_electric_propulsion#List_of_IEP_ships https://en.wikipedia.org/wiki/Integrated_electric_propulsion... and https://en.wikipedia.org/wiki/Columbia-class_submarine#Electric_drive https://en.wikipedia.org/wiki/Columbia-class_submarine#Elect... are to be believed. The latter claims that as of 2013 there is exactly one nuclear submarine class (https://en.wikipedia.org/wiki/Triomphant-class_submarine https://en.wikipedia.org/wiki/Triomphant-class_submarine to be exact) that uses electric engines.
  - digi_owl 9y ago
    I love the way they did the electromagnetic catapult. https://en.wikipedia.org/wiki/Electromagnetic_Aircraft_Launch_System https://en.wikipedia.org/wiki/Electromagnetic_Aircraft_Launc... Basically they spin up flywheels that then dump their kinetic energy back into electric power as the catapult is released. And it allows them to finely adjust the speed of the catapult depending on the kind of aircraft they are launching.
- jasonwatkinspdx 9y ago
  > They're not direct driving the screw with steam power from the reactor heat-exchange, surely. Yes, they are, for the simple reason that it's more efficient. This is beginning to give way to a series electrical design, but that's for reasons of increased stealth and other concerns, at the cost of overall thermodynamic efficiency. On all existing nuclear carriers steam is used for the catapults (and this is much more demanding than many people are aware of). The Ford class is developing electromagnetic catapults, which are also proving to be demanding to perfect.

deleted 9y ago

[deleted]

zwily 9y ago

The heat from the nuclear reaction in a nuclear power plant is typically just used to boil water, which turns turbines, which creates the electricity.

LeifCarrotson 9y ago
Does this electricity charge a battery pack, which then is used to drive the electric motors which turn the screws? This would imply that the heat generation and turbine spin-up time merely need to respond before the batteries are discharged, potentially allowing response times of minutes or hours. It would give Tesla-like instant throttle response, where the operator would move the lever and the sub would jump forward. Or does it directly power the engines? This would mean that your entire control loop would include the latency of the steam generation process. Move the lever, wait for the water to get hot, wait for the turbines to spin up, and then the screws would start to turn faster. Like the throttle response in an ancient diesel truck. Given that the original diesel submarines used giant battery arrays to power the electric motors while the engines were off, and that the former gives much better control response, I'd assume that there are still large batteries in the loop. This paper [2] supports that assertion: > The nominal cell voltage is 2.0 V. [1] The PDX-57 cell designed for Ohio-class submarines weights 2,100 pounds with a capacity of more than 10,000 Amp-hours and stored energy of 2.6 MWh. [1] The ASB-49 cell designed for the Los Angeles-class submarine weights 1,300 pounds with a capacity of 7,200 Amp-hours and stored energy of 1.8 MWh. [1] The LLL-69 type cell weights 1,500 pounds with a capacity of 8,100 Amp- hours and stored energy of 2.0 MHh. [1] A couple megawatthours is plenty to run the screws while the steam loop and nuclear reactor respond. Therefore, toomanybeersies comment: > 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. is technically correct but actually irrelevant. The nuclear reactor telegraph does control the steam turbine and eventually the battery charge, rather than the engine. But somewhere there's an electric motor controller which responds instantly. [1] http://ieeexplore.ieee.org/document/1177196/?reload=true&tp=&arnumber=1177196 http://ieeexplore.ieee.org/document/1177196/?reload=true&tp=... [2] http://large.stanford.edu/courses/2013/ph241/ditiangkin1/ http://large.stanford.edu/courses/2013/ph241/ditiangkin1/
- 9y ago

bzbarsky 9y ago

If https://www.defensetech.org/2013/09/27/ohio-class-subs-to-shift-to-electric-drive/ https://www.defensetech.org/2013/09/27/ohio-class-subs-to-sh... is correct, then at least the Ohio class submarine drives the motor directly off the turbines, but the thing being designed to replace it will use electric motors. And actually, https://en.wikipedia.org/wiki/Columbia-class_submarine#Electric_drive https://en.wikipedia.org/wiki/Columbia-class_submarine#Elect... talks about the same, but with some comments about the few submarine types that do this so far. And following the link to https://en.wikipedia.org/wiki/Integrated_electric_propulsion https://en.wikipedia.org/wiki/Integrated_electric_propulsion gives us https://en.wikipedia.org/wiki/Integrated_electric_propulsion#List_of_IEP_ships https://en.wikipedia.org/wiki/Integrated_electric_propulsion... Looks like some of the most modern or in-design classes are using electric drive, but most things out there are using direct mechanical linkage to the turbines to drive the propeller.