# Weightless in a vacuum holding a dustbuster **URL:** \ **Category:** Factual Questions\ **Created:** [February 21, 2018, 9:38pm UTC](https://boards.straightdope.com/t/weightless-in-a-vacuum-holding-a-dustbuster/809296 "2018-02-21T21:38:13Z")\ **Posts on this page:** 11\ **Page:** 3
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [February 24, 2018, 2:51am UTC](https://boards.straightdope.com/t/weightless-in-a-vacuum-holding-a-dustbuster/809296/41 "2018-02-24T02:51:31Z")
In his new novel _Artemis_, Andy Weir discusses coolant systems for heavy mining machines operating on the moon. Given how carefully he researched _The Martian_, I expect this design exists or is plausible. > [@](#): > > The battery and motor housings are encased in a solid wax reservoir. Melting the wax takes a lot of energy, so that’s where the heat goes. The wax lines are surrounded by coolant pipes. When the harvester comes home to recharge, they pump cold water into those pipes to re-chill the wax… ---
**Author:** ![snfaulkner](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/snfaulkner/32/433_2.png) [@snfaulkner](https://boards.straightdope.com/u/snfaulkner)\ **Post date:** [February 24, 2018, 2:57am UTC](https://boards.straightdope.com/t/weightless-in-a-vacuum-holding-a-dustbuster/809296/42 "2018-02-24T02:57:55Z")
> [@Riemann](#): > > In his new novel _Artemis_, Andy Weir discusses coolant systems for heavy mining machines operating on the moon. Given how carefully he researched _The Martian_, I expect this design exists or is plausible. Sounds similar to what the lunar rover used. Though that was passively cooled. > [@](#): > > LRV batteries and electronics were passively cooled, using change-of-phase wax thermal capacitor packages and reflective, upward-facing radiating surfaces. ---
**Author:** ![msmith537](https://avatars.discourse-cdn.com/v4/letter/m/d9b06d/32.png) [@msmith537](https://boards.straightdope.com/u/msmith537)\ **Post date:** [February 24, 2018, 3:12am UTC](https://boards.straightdope.com/t/weightless-in-a-vacuum-holding-a-dustbuster/809296/43 "2018-02-24T03:12:25Z")
> [@smam](#): > > So, because the hoover hits it’s top speed in say, less than 1 second, I’d also hit my top speed at the same time and stop at the same time it stops? No, I don’t think that’s correct. The Dustbuster is receiving electrical energy from the outlet or battery or whatever. So long as the motor is running, in will continue to increase your angular momentum. Your body has more mass than the Dustbuster parts so it won’t reach top speed as quickly. It will eventually reach the same speed if left unchecked. If you turn the Dustbuster off you will continue to spit at almost the same speed because the friction from the motor slowing down can’t impart enough energy into your large mass. There is still conservation of momentum because the energy is coming from an external source. ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [February 24, 2018, 3:17am UTC](https://boards.straightdope.com/t/weightless-in-a-vacuum-holding-a-dustbuster/809296/44 "2018-02-24T03:17:29Z")
> [@msmith537](#): > > There is still conservation of momentum because the energy is coming from an external source. I should think so. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [February 24, 2018, 3:27am UTC](https://boards.straightdope.com/t/weightless-in-a-vacuum-holding-a-dustbuster/809296/45 "2018-02-24T03:27:52Z")
> [@carnivorousplant](#): > > But how? There are many ways to make sure mechanisms don’t overheat in vacuum: using low power to begin with, making sure there is a _conductive_ heat path from the motor to something larger that can absorb the heat, radiating heat away, using heat pipes or active coolant circulation, phase change material (as already discussed), monitoring the temperature and turning off the power before it overheats, using material that can withstand higher temperatures, etc. I’m pretty sure the [pistol grip tool](https://www.popularmechanics.com/space/a24639/space-drill-used-by-nasa-astronauts/) (basically a cordless driver) is just a low-speed, low-power tool, with temperature sensors that shut down the motor if it starts to overheat. Its maximum speed is only 60 rpm. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [February 24, 2018, 4:04am UTC](https://boards.straightdope.com/t/weightless-in-a-vacuum-holding-a-dustbuster/809296/46 "2018-02-24T04:04:56Z")
**msmith537** , angular momentum is not the same thing as energy, and both must be conserved. While the motor’s rotation is accelerating, so is yours. When the motor reaches its top speed, so do you. When the motor stops, so do you. There is no other way to conserve the angular momentum, and the fact that there’s an energy source is completely irrelevant to the conservation of angular momentum. ---
**Author:** ![TonySinclair](https://avatars.discourse-cdn.com/v4/letter/t/49beb7/32.png) [@TonySinclair](https://boards.straightdope.com/u/TonySinclair)\ **Post date:** [February 24, 2018, 4:21am UTC](https://boards.straightdope.com/t/weightless-in-a-vacuum-holding-a-dustbuster/809296/47 "2018-02-24T04:21:34Z")
Am I the only one childish enough to think that you would be getting a visit from the Department of Redundancy Department for using a vacuum in a vacuum? ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [February 24, 2018, 5:30am UTC](https://boards.straightdope.com/t/weightless-in-a-vacuum-holding-a-dustbuster/809296/48 "2018-02-24T05:30:32Z")
> [@msmith537](#): > > No, I don’t think that’s correct. The Dustbuster is receiving electrical energy from the outlet or battery or whatever. So long as the motor is running, in will continue to increase your angular momentum. No. Angular momentum is proportional to rotational speed. Once the motor reaches a constant rotation speed, its angular momentum is constant. > [@](#): > > Your body has more mass than the Dustbuster parts so it won’t reach top speed as quickly. It will eventually reach the same speed if left unchecked. No. Because your body has more mass than the rotating parts of the Dustbuster, _it will reach a lower top speed_. But it will reach that speed when the motor reaches its top speed. It’s the _acceleration_ of the motor that’s accelerating your body’s rotation. > [@](#): > > If you turn the Dustbuster off you will continue to spit at almost the same speed because the friction from the motor slowing down can’t impart enough energy into your large mass. No. If you turn off the Dustbuster, its rotating parts will come to a stop due to friction. Throughout all this, the angular momentum of the astronaut+dustbuster is conserved, so when the Dustbuster stops, everything will stop spinning. > [@](#): > > There is still conservation of momentum because the energy is coming from an external source. I’m not really sure what you mean. It doesn’t matter where the energy comes from. Energy and angular momentum are completely different things. You can’t convert one to the other. ---
**Author:** ![msmith537](https://avatars.discourse-cdn.com/v4/letter/m/d9b06d/32.png) [@msmith537](https://boards.straightdope.com/u/msmith537)\ **Post date:** [February 24, 2018, 12:29pm UTC](https://boards.straightdope.com/t/weightless-in-a-vacuum-holding-a-dustbuster/809296/49 "2018-02-24T12:29:32Z")
Yeah, never mind what I said. I was thinking that it worked like applying a force where you would keep accelerating, but it doesn’t. And now everyone on the OP’s spaceship is dead. ---
**Author:** ![Sam\_Stone](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Sam\_Stone](https://boards.straightdope.com/u/Sam_Stone)\ **Post date:** [February 24, 2018, 7:09pm UTC](https://boards.straightdope.com/t/weightless-in-a-vacuum-holding-a-dustbuster/809296/50 "2018-02-24T19:09:31Z")
> [@Saint\_Cad](#): > > IIRC early planes had propellers that turned in opposite directions to prevent torque on the aircraft. Not quite, or at least not complete. When a propeller is perpendicular to the airflow, the thrust load on the propeller disc is even and the thrust goes down the centerline of the engine. However, when the propeller disc is tilted against the incoming airflow as in a climb, the angle of attack of the blades is different on each side of the propeller. This causes asymmetric disc loading, and the centerline of the thrust is offset from the engine. When propellers rotate in the same direction, one engine’s thrust line will be inboard of the engine, and the other outboard of the engine. This can cause all kinds of handling issues. By having both engines rotate in different directions, you can either move both thrustlines inboard, which eliminates the critical engine and makes handling easier on single engine failure, or you can rotate them so that the thrustline is outboard of the engines, which can improve yaw stability. ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [February 26, 2018, 10:51pm UTC](https://boards.straightdope.com/t/weightless-in-a-vacuum-holding-a-dustbuster/809296/51 "2018-02-26T22:51:19Z")
> [@msmith537](#): > > Yeah, never mind what I said. I was thinking that it worked like applying a force where you would keep accelerating, but it doesn’t. And now everyone on the OP’s spaceship is dead. Nice job breaking it Hero. [Previous page](https://boards.straightdope.com/t/weightless-in-a-vacuum-holding-a-dustbuster/809296.md?page=2)