For Questions That Don't Merit Their Own Thread

[K^2]

2 minutes ago, MaverickSawyer said:

Those are chipmunks, not squirrels... and there's a reason I've always referred to them as "minibears".

In places I've seen these in US, they've been pretty shy with people, but they get aggressive when they think they can get in and get out before anyone even sees them. And they're usually right! On a few occasions I've had food go missing, with the last thing I'd see being a brown blur with black stripes disappearing into the bushes.

[MaverickSawyer]

32 minutes ago, K^2 said:

In places I've seen these in US, they've been pretty shy with people, but they get aggressive when they think they can get in and get out before anyone even sees them. And they're usually right! On a few occasions I've had food go missing, with the last thing I'd see being a brown blur with black stripes disappearing into the bushes.

In the more heavily trafficked areas, they're a lot less skittish, and hell of a lot more bold. One tried to climb my boot one time in Yosemite... Only the fact that there were bystanders who wouldn't understand kept me from giving that minibear a flying lesson. >_>

[StrandedonEarth]

In Vancouver’s Stanley Park (the famous park and a famous Cup are both named after Lord Stanley) the grey squirrels will climb all the way up your leg for food. 

[ARS]

On electric vehicles, which uses electric motor for propulsion, is it possible to use high-energy capacitors as sort of "nitro boost" by discharging massive amount of electric energy to the electric motors? Does it have a side effect? Like a danger of motors getting overloaded and explodes?

[0111narwhalz]

44 minutes ago, ARS said:

On electric vehicles, which uses electric motor for propulsion, is it possible to use high-energy capacitors as sort of "nitro boost" by discharging massive amount of electric energy to the electric motors? Does it have a side effect? Like a danger of motors getting overloaded and explodes?

Increasing the current will probably slag the motor. Increasing the voltage might yield the results you expect. There was a restriction on cell count when I raced RC cars, which implies that more cells (i.e. more voltage) leads to an advantage. Also, the near-flat voltage curve with charge that is characteristic of lithium batteries helped immensely, so I think motor performance is related tightly to voltage. Capacitors' voltage curves are… not even slightly flat.
If you overvolt a motor too much, you can probably expect issues involving insulation and shorts.

[Gargamel]

17 hours ago, MaverickSawyer said:

Those are chipmunks, not squirrels... and there's a reason I've always referred to them as "minibears".

Somebody has been to Philmont!    I watched a crew from Japan de-pack and line up their packs in a row at one base, one of the kids must have had something tasty open in his pack, because a swarm of minibears just descended and tore the upper compartment of his pack to shreds. 

Edited November 18, 2018 by Gargamel

[MaverickSawyer]

29 minutes ago, Gargamel said:

Somebody has been to Philmont!    I watched a crew from Japan de-pack and line up their packs in a row at one base, one of the kids must have had something tasty open in his pack, because a swarm of minibears just descended and tore the upper compartment of his pack to shreds. 

I never went myself, but I learned the name from someone who did.

 

And yeah, annoying little rascals they are, they attempted to gnaw through a polycarbonate bear canister to get at the food inside one backpacking trip. It was a great example to the new scouts of why you stow your food.

[K^2]

10 hours ago, ARS said:

On electric vehicles, which uses electric motor for propulsion, is it possible to use high-energy capacitors as sort of "nitro boost" by discharging massive amount of electric energy to the electric motors? Does it have a side effect? Like a danger of motors getting overloaded and explodes?

Excessive current through motor's coils will cause it to overheat, but current is proportional to torque, so effectively, if you don't plan to exceed max torque, you're fine. And the reason you might want a boost for it is that as motor RPM goes up, so does back EMF of the coils. So you get lower current at the same applied voltage. You can boost the voltage in several ways, but that still increases load on battery, and that's where you can bring in supercaps. So yeah, completely viable. And you can even use regenerative braking to recharge them, so it need not be a one time boost.

[magnemoe]

On 11/18/2018 at 12:50 AM, 0111narwhalz said:

Increasing the current will probably slag the motor. Increasing the voltage might yield the results you expect. There was a restriction on cell count when I raced RC cars, which implies that more cells (i.e. more voltage) leads to an advantage. Also, the near-flat voltage curve with charge that is characteristic of lithium batteries helped immensely, so I think motor performance is related tightly to voltage. Capacitors' voltage curves are… not even slightly flat.
If you overvolt a motor too much, you can probably expect issues involving insulation and shorts.

The engine has to be designed for it and more important the power system  but as I understand cell count limit the power draw you can get out of an electrical battery, so more cells give an both more power and longer range. 
This is also why larger solid state disks tend to be faster as they can read from multiple chips in parallel. 
So yes you could use an ultacap as an boost on an electrical car. 
 

Remember we did dragracing and jumping, running the 6 V cars in car tracks powered by an car battery. it worked as the cars was on an open track so they was just overvolted for some seconds  

[Terwin]

On 11/17/2018 at 12:38 AM, K^2 said:

I think that's a good chunk of it. European squirrels are a lot more shy with humans, in my experience. I've never seen one closer than on a tree branch five meters off the ground, hiding behind the trunk from me as if I still pose some sort of a danger. In contrast, squirrels in N.A. tend to feel pretty comfortable looking for food 3 meters from a person, unless said person starts moving towards them. And that's in suburbs. In some of the more touristy places, where people feed them, they tend to get almost as shameless as pigeons. I've had one come up to me in Boston, and when I squatted to take a closer look, it actually grabbed my hand to see if I have any food for it. Once it saw no food, it got disappointed and left. Can't picture European squirrel pull something like that.

That said, in some parts of USA (e.g. Midwest, parts of Cali), Canadian black squirrels seem to be pushing out the gray locals. That seems to be just stronger territorial aggressiveness, though, rather than any special interaction with humans. Unless there is some more subtle adaptation that I'm not aware of.

Some places north american gray squirrels will come up and take food from your hand(while the others empty your lunchbox), and tell you off if you don't let go!  (Thinking of the West Mall on the University of Texas at Austin where many students feed the squirrels, intentionally or not)

[mikegarrison]

[mhoram]

Apparently a researcher team managed to use ion engines in the atmosphere.

https://www.scientificamerican.com/article/silent-and-simple-ion-engine-powers-a-plane-with-no-moving-parts/

[SuperFastJellyfish]

4 hours ago, mhoram said:

Apparently a researcher team managed to use ion engines in the atmosphere.

https://www.scientificamerican.com/article/silent-and-simple-ion-engine-powers-a-plane-with-no-moving-parts/

This merited a thread. 

[munlander1]

If one of the Gemini pilots was incapacited during the mission, would the other pilot be able to fly?

[max17]

If you were to fart in space would you be atleast a little bit propelled?

[munlander1]

3 minutes ago, max17 said:

If you were to fart in space would you be atleast a little bit propelled?

I don’t think it would be noticeable, but yes.

[kerbiloid]

4 hours ago, max17 said:

If you were to fart in space would you be atleast a little bit propelled?

Especially inside the cabin. They will provide the initial acceleration with a kick.

5 hours ago, munlander1 said:

If one of the Gemini pilots was incapacited during the mission, would the other pilot be able to fly?

 Gemini-1

[magnemoe]

3 hours ago, kerbiloid said:

 Gemini-1

Spaceships tend to be very remote controllable. The astronauts even had to fight to be allowed to control them in the start. 

And it would make perfect sense to have both astronauts share the basic controls in an side by side setup. 

And yes an fart would be an cold gas truster. Now this would require you to have no pants and would therefor best been done inside an space station. 
An space station is an closed air system with other astronauts, you are likely to get more speed because they throw stuff at you at least with repeated experiments. 
I also don't think it will give much trust because of the badly designed nozzle and the propellant having low speed and mass. 

[kerbiloid]

dV_spaceship = M_experimenter/M_spaceship * dV_{experimenter thrown out}

[max17]

4 hours ago, magnemoe said:

Spaceships tend to be very remote controllable. The astronauts even had to fight to be allowed to control them in the start. 

And it would make perfect sense to have both astronauts share the basic controls in an side by side setup. 

And yes an fart would be an cold gas truster. Now this would require you to have no pants and would therefor best been done inside an space station. 
An space station is an closed air system with other astronauts, you are likely to get more speed because they throw stuff at you at least with repeated experiments. 
I also don't think it will give much trust because of the badly designed nozzle and the propellant having low speed and mass. 

LOL "Badly designed nozzle" 

[ARS]

Why the ball-shaped design of reentry capsule in Vostok spacecraft (That carried first man in space) isn't used anymore? Most reentry capsule today seems using the roughly conical design

Also, unrelated, but is there any free software to "degrade" the resolution of the video? Like, I had a 720p video that I wanna degrade to 360p?

[Gargamel]

5 minutes ago, ARS said:

Why the ball-shaped design of reentry capsule in Vostok spacecraft (That carried first man in space) isn't used anymore? Most reentry capsule today seems using the roughly conical design

I know others will have better answers, but a conical pod is steerable.  You can change the angle of attack on re-entry to change it's flight path a bit. 

[Xd the great]

1 hour ago, ARS said:

 

Also, unrelated, but is there any free software to "degrade" the resolution of the video? Like, I had a 720p video that I wanna degrade to 360p?

1. Upload to youtube. 

2. Watch video and screen record at 360p.

1 hour ago, Gargamel said:

I know others will have better answers, but a conical pod is steerable.  You can change the angle of attack on re-entry to change it's flight path a bit. 

This allows for a far lower gee forces during reentry. Aka more survivable.

For comparison, 9 vs 3 gees for LEO reentry, 39 vs 4 gees for lunar reentry.

[kerbiloid]

6 hours ago, ARS said:

Why the ball-shaped design of reentry capsule in Vostok spacecraft (That carried first man in space) isn't used anymore? Most reentry capsule today seems using the roughly conical design

And by steering the conic capsule you can decrease the overload from 8-10 g down to 3-4.

If use a winged reentry vehicle or a lifting body you can achieve even 2-3 g on reentry and pay less to the crew because you need no supermen anymore.

***

Though, spheres are still used in the uncrewed Vostok-derived sats.

***

The last variant of the Spiral pilot escape capsule was spherical, while the original one was conical.
Because they had to.

Edited November 25, 2018 by kerbiloid

[Xd the great]

6 hours ago, ARS said:

Why the ball-shaped design of reentry capsule in Vostok spacecraft (That carried first man in space) isn't used anymore? Most reentry capsule today seems using the roughly conical design

Also, the capsules offer steering by rolling and offsetting the CoM. You can try that in ksp.