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For Questions That Don't Merit Their Own Thread

Skyler4856

By Skyler4856
in Science & Spaceflight

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kerbiloid

kerbiloid

Posted
Posted

There was an old sci-fi story with a robomule.

We need a kind of Boston-like robohorse in case of a time portal gets unexpectedly opened during the ITER and LHA experiments, like in Stargate, but into the medieval or ancientry.

Also, there is another problem: what should be the time traveller's weapon, as the assault rifles are an obvious overkill.

(Except the red crowbar which is present by default.)

(Every self-respecting scientist always keeps it at hands, after the case happened to Gordon Freeman.)

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Hyperspace Industries

Hyperspace Industries

Posted
Posted

Is there something easier to get than potassium nitrate (and I mean a lot easier, as in, every grocery store and petrol station has some) that could work as an oxidizer for a sugar rocket.

 

I apologize in advance if the following bit sounds a bit angry:

(And don't go telling me that hydrogen peroxide isn't impossible to buy, or that ammonium nitrate or whatever is available at any corner store, I ain't in no northern hemisphere country where you can buy those fancy chemical stuff.)

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JoeSchmuckatelli

JoeSchmuckatelli

Posted
Posted
Just now, Hyperspace Industries said:

Is there something easier to get than potassium nitrate (and I mean a lot easier, as in, every grocery store and petrol station has some) that could work as an oxidizer for a sugar rocket.

 

I apologize in advance if the following bit sounds a bit angry:

(And don't go telling me that hydrogen peroxide isn't impossible to buy, or that ammonium nitrate or whatever is available at any corner store, I ain't in no northern hemisphere country where you can buy those fancy chemical stuff.)

Most places enjoy selling people bomb incendiary rocket precursor chemicals to the general public

If that doesn't work - get on Chinese Amazon.  You can buy anything there 

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monophonic

monophonic

Posted
Posted
On 2/5/2022 at 12:37 AM, JoeSchmuckatelli said:

Interesting - I just learned one of the downsides to EV in-wheel motors:

Why don't EVs have four in-wheel motors? - EV Central

Interesting - I think all of those issues have been mostly solved by the tram industry. Of course trams have much higher weight and financial budgets so the e.g. the weight issue may simply be moot for them - and the cost obviously is.  Maybe the carmakers have already looked there for solutions and found that those solutions do lie outside the limits of regular road vehicles?

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K^2

K^2

Posted
Posted
26 minutes ago, monophonic said:

Interesting - I think all of those issues have been mostly solved by the tram industry. Of course trams have much higher weight and financial budgets so the e.g. the weight issue may simply be moot for them - and the cost obviously is.  Maybe the carmakers have already looked there for solutions and found that those solutions do lie outside the limits of regular road vehicles?

I think, for cars, the problems are compounded by the vibration. As mentioned in the article, one of the problems of wheels is that they have to be the first line of defense against the road surface being less than perfect, before the suspension. This gets even worse for low-profile wheels of sportier cars, where the tires have to be stiffer by design. Rolling on rails just doesn't come with the same sort of problems.

Trying to house the wheels and the brakes in the wheels of a car is hard enough. Doing so in a way that doesn't greatly increase weight and will survive driving over hundreds of potholes and speed bumps? That's next level.

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magnemoe

magnemoe

Posted
Posted
46 minutes ago, K^2 said:

I think, for cars, the problems are compounded by the vibration. As mentioned in the article, one of the problems of wheels is that they have to be the first line of defense against the road surface being less than perfect, before the suspension. This gets even worse for low-profile wheels of sportier cars, where the tires have to be stiffer by design. Rolling on rails just doesn't come with the same sort of problems.

Trying to house the wheels and the brakes in the wheels of a car is hard enough. Doing so in a way that doesn't greatly increase weight and will survive driving over hundreds of potholes and speed bumps? That's next level.

Rails are much smoother, as it they don't have many potholes and speed bumps. And as you say weight don't matter so much. For cars room in wheels are limited because you need room for the brakes and fit inside an replaceable rim.  You also want to minimize the weight of the wheel because of suspension and the engine has to handle all the beating as its not suspended. 
In short for performance cars you don't want it even if you have 4 motors. 

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JoeSchmuckatelli

JoeSchmuckatelli

Posted
Posted

Back to my 'regularly scheduled theme' of quirky gravity questions:

Preamble: I know that 3-body problems are complex... but do we have a guess as to what effect the sun's motion around Sag A has on the orbits of the planets?

(I'm guessing that Sag A gravity affects the whole system, not just the sun, but given the sun's massive gravity compared to its satellites... is it correct to assume that orbits are solely determined by the sun?)

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Jacke

Jacke

Posted
Posted
14 minutes ago, JoeSchmuckatelli said:

Back to my 'regularly scheduled theme' of quirky gravity questions:

Preamble: I know that 3-body problems are complex... but do we have a guess as to what effect the sun's motion around Sag A has on the orbits of the planets?

(I'm guessing that Sag A gravity affects the whole system, not just the sun, but given the sun's massive gravity compared to its satellites... is it correct to assume that orbits are solely determined by the sun?)

Sag A*'s gravity is near constant across the whole solar system.  It's the differences that matter.

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kerbiloid

kerbiloid

Posted
Posted (edited)

R = 27 000 ly ~= 2.55*1020 m

V ~= 220 km/s = 2.2*105 m/s.

gSagA* = V2 / R = (2.2*105)2 /  (2.55*1020) ~= 1.9*10-10 m/s2 ~= .2*10-11 g

The area where its gravity affects a lot, we usually call "accretion disk".

Edited by kerbiloid
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JoeSchmuckatelli

JoeSchmuckatelli

Posted
Posted (edited)
5 hours ago, kerbiloid said:

R = 27 000 ly ~= 2.55*1020 m

V ~= 220 km/s = 2.2*105 m/s.

gSagA* = V2 / R = (2.2*105)2 /  (2.55*1020) ~= 1.9*10-10 m/s2 ~= .2*10-11 g

The area where its gravity affects a lot, we usually call "accretion disk".

See - you're hitting on something thats niggling the back of my brain.  Given that we generally assume at a given radii that all things will have the same orbital speed, and that those are usually done looking at just planets or just satellites of planets... (mostly because the satellite is so, so very much less than the sun / planet in question)

Is there any reason to think that the sun's gravity might combine with that of Sag A to give it a smidge more speed, and the planets over time start to lag a bit, having to be pulled back into the sun's orbit by the sun itself... making Sag A's influence not entirely constant over the entire system?  

*and yeah, I know that the sun is so, so, so, very much less than Sag A... but given how much bigger it is than any other planet - could there be an effect?

 

Edit - or am I once again revealing my fundamental misunderstanding of how gravity works? 

Edited by JoeSchmuckatelli
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kerbiloid

kerbiloid

Posted
Posted
8 hours ago, JoeSchmuckatelli said:

Is there any reason to think that the sun's gravity might combine with that of Sag A to give it a smidge more speed, and the planets over time start to lag a bit, having to be pulled back into the sun's orbit by the sun itself... making Sag A's influence not entirely constant over the entire system?  

*and yeah, I know that the sun is so, so, so, very much less than Sag A... but given how much bigger it is than any other planet - could there be an effect?

Sag A* mass is ~4 * 106 Sun masses.

1 l.y. / 1 AU ~= 9.5*1015 / 1.5*1011 ~=6.3 * 104 times.

Distance to Sag A* / distance to Sun ~= 27 000 * 6.3*104 ~= 1.7*109 times.

Gravitational acceleration from Sag A* / from Sun ~= 4.*106 / 1.7*109 ~=0.0024 times.

So, if we were 20 times closer to Sag A*,  or 20 times farther from the Sun, than now, its gravitation for us would be equal to the solar one, but this would be the smallest of our problems.

Currently it causes perturbations significant for the precise theory of the Moon motion and for the Kuiper belt.

(As all planets of the Solar system are anyway pulled by it  with same acceleration together.)

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K^2

K^2

Posted
Posted
15 hours ago, JoeSchmuckatelli said:

Is there any reason to think that the sun's gravity might combine with that of Sag A to give it a smidge more speed, and the planets over time start to lag a bit, having to be pulled back into the sun's orbit by the sun itself... making Sag A's influence not entirely constant over the entire system?

That's just a general case of a tidal force. It goes down as a cube of the distance from source and grows linearly with the size of the system influenced by tidal forces. As size of the Solar System is pretty much negligible compared to the distance to Sag A*, the effect is, technically, there, but it's not significant at all.

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JoeSchmuckatelli

JoeSchmuckatelli

Posted
Posted

I've been sitting here thinking about the responses to my recent question... and suddenly got hit with this uncomfortable realization of just how freaking massive Sag A must be.

(It's one thing to know something intellectually, but another to feel it).

The numbers are so big they almost don't make sense.  Like trying to parse out what Kraftfahrzeughaftpflichtversicherung means when you know the root words - but are barely fluent in the language itself.

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TheSaint

TheSaint

Posted
Posted
4 hours ago, Admiral Fluffy said:

PANIC!

I don't think panic would do anybody much good. I personally would pour myself one last, very large adult beverage and watch the show.

Reminds me of when we went diving in Australia. Divemaster is giving the dive brief. "In this area, you may see stone fish. Be very careful, because they are extremely dangerous. If you get stung by a stone fish, here is what you do: Proceed immediately to the surface. Get back onto the dive boat as fast as you can. Then drink a six-pack of beer, because it's the last one you're ever going to have."

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K^2

K^2

Posted
Posted
11 hours ago, TheSaint said:

Reminds me of when we went diving in Australia. Divemaster is giving the dive brief. "In this area, you may see stone fish. Be very careful, because they are extremely dangerous. If you get stung by a stone fish, here is what you do: Proceed immediately to the surface. Get back onto the dive boat as fast as you can. Then drink a six-pack of beer, because it's the last one you're ever going to have."

I find these instructions somewhat questionable. "We found no traces of stone fish venom. He must have mistaken something else for it." - "Wait, so what killed him?" - "The bends."

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tomf

tomf

Posted
Posted

You would have to be spectacularly unlucky to get fatal DCI from the type of diving I am sure the Saint was doing, whereas even a mild reaction to stonefish, which is rarely fatal on its own is going to be extremely hazardous under water. (Source: been bent twice)

Bends can be treated, drowning not so much

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JoeSchmuckatelli

JoeSchmuckatelli

Posted
Posted

Not exactly 'spacey' science - but a surprisingly good article about a Nobel nominee who co-created a cheap covid vaccine that they're giving away for free (to countries). 

https://www.nbcnews.com/news/latino/latina-scientist-co-created-new-covid-vaccine-nominated-nobel-peace-pr-rcna15173

... 

In other news - we keep inching closer to Fusion. 

 
Quote

 

Experts say the results prove that nuclear fusion is possible, and no longer a pipedream solution for the climate crisis.
"These landmark results have taken us a huge step closer to conquering one of the biggest scientific and engineering challenges of them all," said Ian Chapman

 

 

5 seconds sustained, but so hot it likely burnt out Oxford's Tokamak 

https://www.cnn.com/2022/02/09/uk/nuclear-fusion-climate-energy-scn-intl/index.html

 

 

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