For Questions That Don't Merit Their Own Thread

[andrewas]

The nit is that, if you don't have your orientation, then observation of the sun and a single planet does not give you your position, the two lines can intersect anywhere on a circle. Observing a third planet gives you a complete fix, or getting your orientation from the background stars gives you a complete fix.

[peadar1987]

[quote name='ZetaX']Actually it is only always day. You would need a rather weird definition of "night" to be able to claim otherwise.
Yes, it is dark, but I wouldn't take anyone seriously who closes the curtains at noon and then proclaims "night". Seeing stars also can't be it, otherwise every cloudy day is "night". And so on.[/QUOTE]

Your spacecraft will have a "night side" and a "day side".

I, on the other hand, only have a nitpicking side ;)

[Superfluous J]

[quote name='andrewas']The nit is that, if you don't have your orientation, then observation of the sun and a single planet does not give you your position, the two lines can intersect anywhere on a circle. Observing a third planet gives you a complete fix, or getting your orientation from the background stars gives you a complete fix.[/QUOTE]

But the ability to see every single star in the sky makes that 3rd planet unnecessary. They are giving you your orientation.

[technion]

Thanks for all this. The concept is quite obvious, I guess I just didn't expect it to be accurate.

You're shooting at Pluto from a long way away. 0.1degrees means a lot, yet you're just looking at the position of a star and declaring you know where you are.

[Superfluous J]

[quote name='technion']Thanks for all this. The concept is quite obvious, I guess I just didn't expect it to be accurate.

You're shooting at Pluto from a long way away. 0.1degrees means a lot, yet you're just looking at the position of a star and declaring you know where you are.[/QUOTE]

Well they also use top of the line telescopes and lots and lots of computers. But yeah. That's essentially it.

The cool part about NH? It wasn't just tracking its own position, but [b]Pluto[/b]'s. They wanted to hit such a specific spot that the current (at the time) estimates of Pluto's orbit weren't good enough, and they had to track it on the way in.

[Bill Phil]

What applications could nuclear isomers have? And could there be isomers of stable isotopes?

[Wjolcz]

[quote name='K^2']That doesn't sound right. Do you have a link and time-stamp to where he says that?[/QUOTE]

I don't. But it's the one where he finally gets the Alcubierre ring, or however it's called and goes to Dres. I'm on mobile right now so it's not very easy to post is here.

[andrewas]

Episode 96, just after 12 minutes. He actually states that if you go *faster* than light, you can send messages into the past.

[gooddog15]

Why are RD-180 engine nozzles painted white?
[IMG]http://spacenews.com/wp-content/uploads/2014/11/RD180_NASA4X3_0.jpg[/IMG]

[More Boosters]

Why do we particularly care if our spacecraft to Mars are sterilized? They're unlikely to survive that trip, and if they do, isn't it a boon? Something to study?

I mean is it really expected that Earth bacteria would go there and then survive and even kill off native life? Isn't it a good thing if our bacteria can actually survive there?

[micr0wave]

look at [URL="https://en.wikipedia.org/wiki/Tardigrade"]those[/URL], they're classified as animals actually, and can survive a trip to space

[More Boosters]

[quote name='micr0wave']look at [URL="https://en.wikipedia.org/wiki/Tardigrade"]those[/URL], they're classified as animals actually, and can survive a trip to space[/QUOTE]

I know they can, I mean the sterilization they do when going to Mars.

[Camacha]

[quote name='More Boosters']I mean is it really expected that Earth bacteria would go there and then survive and even kill off native life? Isn't it a good thing if our bacteria can actually survive there?[/QUOTE]

The last bit I have always agreed with. Even if our species or planet does not survive, we would have seeded life across the solar system and maybe even beyond.

However, in the case of Mars and other potential Earth-like life bearing places, it is very hard to look for life if you brought some along with you, even if in a different landing site. You need to understand that actually going out and looking for the things themselves is the last step of the process of finding life. Before that stage, you look at other clues, like substances and materials that are associated with life. Those values get messed up if you bring life along yourself. Current missions trying to find out about life would not be able to detect the actual life, the living things. It detects things probably associated with them.

Finding a needle in a haystack is a lot easier if you do not introduce a dozen of your own needles that do not need finding. That is even without considering the possibility of 'our' type of life out competing Martian life, destroying something unique forever.

Introducing life elsewhere is a good way of hedging your bet, but the major downside is that you inevitably destroy local circumstances in the process. History shows us that might not be a great idea.

[More Boosters]

[quote name='Camacha']The last bit I have always agreed with. Even if our species or planet does not survive, we would have seeded life across the solar system and maybe even beyond.

However, in the case of Mars and other potential Earth-like life bearing places, it is very hard to look for life if you brought some along with you, even if in a different landing site. You need to understand that actually going out and looking for the things themselves is the last step of the process of finding life. Before that stage, you look at other clues, like substances and materials that are associated with life. Those values get messed up if you bring life along yourself. Current missions trying to find out about life would not be able to detect the actual life, the living things. It detects things probably associated with them.

Finding a needle in a haystack is a lot easier if you do not introduce a dozen of your own needles that do not need finding. That is even without considering the possibility of 'our' type of life out competing Martian life, destroying something unique forever.

Introducing life elsewhere is a good way of hedging your bet, but the major downside is that you inevitably destroy local circumstances in the process. History shows us that might not be a great idea.[/QUOTE]

If we can permanently destroy martian life with the handful of stuff that may survive, it is probably too rare to begin with. I'm not sure if you can compare Mars to Earth, Earth has ridiculous amounts of the stuff while Mars has been taking its sweet time in revealing the life there.

Would tardigrades or whatever else that can survive there even be able to sustain simply off the Martian air, Martian soil and the dimmed sunlight?

[Camacha]

[quote name='More Boosters']If we can permanently destroy martian life with the handful of stuff that may survive, it is probably too rare to begin with.[/quote]

What do you mean by that? Martian life will almost certainly be having a harder time than Earth life.


[quote]Would tardigrades or whatever else that can survive there even be able to sustain simply off the Martian air, Martian soil and the dimmed sunlight?[/QUOTE]

It might, it might not, but we cannot take the risk of destroying something so profound.

[AngelLestat]

Physics problem:

If I have a long rope in tension, lets said 2000m.  If I pull one extremity of the rope, how much time it will take the pull force to reach the end?

This is the same than waves?  Where the tension force is the one that dictates the speed of the wave?  This has something to do with the material used in the rope?

Edited December 3, 2015 by AngelLestat

[kunok]

1 hour ago, AngelLestat said:

Physics problem:

If I have a long rope in tension, lets said 2000m.  If I pull one extremity of the rope, how much time it will take the pull force to reach the end?

This is the same than waves?  Where the tension force is the one that dictates the speed of the wave?  This has something to do with the material used in the rope?

IIRC the "force" in a material travels at the speed of the sound in that material.

[AngelLestat]

thank you very much kunok!!

I imagine that was something related to the speed of sound, but I could not find nothing in my previous search on google.

But I guess I was using the wrong keywords.  Have a nice day.

[RainDreamer]

How big a satellite has to be, and in which orbit it should be, to cause an artificial solar eclipse that can be observed with the naked eyes?

Also, is it likely for solar sails craft to cause this to happen?

[cubinator]

Found this with a quick Google search. That's the ISS going by the Sun and Moon. It's already really big, so something would have to be even bigger to make an eclipse that big. A satellite in low orbit that is dozens of kilometers across is not feasible, and it wouldn't even make a very big shadow. I don't think solar sails will be anywhere near big enough because they are basically carrying tiny satellites at the moment, and unless you want to make one for the ISS, you're going to have to squint really hard. As for the orbit, it doesn't really matter as long as it occasionally makes a shadow across Earth's surface.

[Motokid600]

I cannot for the life of me find a picture of a fuel tank with a concave end to it. How is this achieved exactly?

Same thing with the upper stage of the Saturn V. One fuel tank has a concave end to it for better space utilization. Can't find any information on this.

[andrewas]

Its one tank with a divider in it to separate oxidizer from fuel. In this case, the divider is domed and faced downwards because the LOX in the lower part of the tank is at higher pressure than the alcohol in the top tank.

[RainDreamer]

This thread should be pinned. So hard to find it.

Anyway, my question right now is: is there any significant increase in explosive yield when you launch a nuke with faster speed (by, say, a rail gun)?

One of the game I was playing has a space ship launching nukes using railgun to accelerate it to hyper velocity, and I wonder if it makes the nuke any more explody.

[ZetaX]

2 hours ago, RainDreamer said:

This thread should be pinned. So hard to find it.

Anyway, my question right now is: is there any significant increase in explosive yield when you launch a nuke with faster speed (by, say, a rail gun)?

One of the game I was playing has a space ship launching nukes using railgun to accelerate it to hyper velocity, and I wonder if it makes the nuke any more explody.

Theoretically, yes. Practically. no. You would need to accelerate it to reletivistic speeds for this to truly matter. At some point the blast will also become more and more cone-shaped.

[AngelLestat]

3 hours ago, RainDreamer said:

This thread should be pinned. So hard to find it.

Anyway, my question right now is: is there any significant increase in explosive yield when you launch a nuke with faster speed (by, say, a rail gun)?

One of the game I was playing has a space ship launching nukes using railgun to accelerate it to hyper velocity, and I wonder if it makes the nuke any more explody.

This nuke detonates before it reaches its target?  Because if dont.. then you may have only the kinetic energy.
If explodes in the air, then it only increase the explosive energy in the kinetic direction, in the opposite direction I guess decrease.

It also depends on the speed magnitud we are talking about.  Close to the speed of light it will be similar or greater than that amount of mass in antimatter.  I will need to make better calculations to confirm that.