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Suddenly, It Seems, Water Is Everywhere in Solar System

nytimes.com

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Re: Suddenly, It Seems, Water Is Everywhere in Solar System

#71

Post by throwaway_yy2Di »

Symmetry wrote: post #34
Mahn wrote: post #28

Does anyone else think NASA should reconsider their plans for a manned mission to Mars? With Europe, Ceres, Enceladus, Ganymede and many more promising moons out there it seems kind of a waste to spend time, effort and capital in Mars now.

Europa is a lot further away than Mars [1]. Every extra 4600 m/s of delta V in the mission means another factor of e in the ratio of initial to payload mass. At least until we develop better high efficiency rockets. [1] http://i.imgur.com/AAGJvD1.png

In practice, the ΔV differences are actually way smaller than that chart suggests. Those figures are for direct transfers (per the legend). But if you allow indirect trajectories with gravity assists [0], that makes things drastically cheaper. To intercept Jupiter, you can steal much of the needed ΔV from flybys of the inner planets (at the tradeoff of time, waiting to go around the sun multiple times). And maneuvering within Jupiter's gravity well can be practically free, by flybys of the Galilean moons. The map tells you 8,890 m/s to intercept Europa, which would be horrifying, but none of that actually needs to be propulsion.

[0] https://en.wikipedia.org/wiki/Gravity_assist

Re: Suddenly, It Seems, Water Is Everywhere in Solar System

#72

Post by ecobiker »

Grazester wrote: post #69
PhoenixWright wrote: post #52

Growing up this was a huge question that nobody knew the answer to. I don't remember the first discovery of water but I do remember reading one after another water finding. Back then water = life and if we found water it was very likely we would find some form of life. I've already read articles talking about microbial life but I think we will soon discover a variety of living forms. That being said I don't think our…

>But what life, in some form, demonstrates is that it is possible, in some place very far away, there are living beings as advanced or more than we are. I would really love to be alive to meet them. Assuming that they are benign and non threatening but I wouldn't take my chances. I dont hope for this.

I understand where this concern comes from. But what I'm unable to reconcile is if a life form can get more "advanced" or even survive long without knowing co-operation and in general being more civilized - Live and let live? Or to point the question inward, let's say humans continue(d) their indiscriminate slaughter of fellow humans and animals around us would we still survive long enough?

Re: Suddenly, It Seems, Water Is Everywhere in Solar System

#73

Post by pwnna »

throwaway_yy2Di wrote: post #71
Symmetry wrote: post #34

Earlier quoted context omitted.

Europa is a lot further away than Mars [1]. Every extra 4600 m/s of delta V in the mission means another factor of e in the ratio of initial to payload mass. At least until we develop better high efficiency rockets. [1] http://i.imgur.com/AAGJvD1.png

In practice, the ΔV differences are actually way smaller than that chart suggests. Those figures are for direct transfers (per the legend). But if you allow indirect trajectories with gravity assists [0], that makes things drastically cheaper. To intercept Jupiter, you can steal much of the needed ΔV from flybys of the inner planets (at the tradeoff of time , waiting to go around the sun multiple times). And maneuver…

Keep in mind, for a human mission, you want to minimize time, rather than deltaV. Gravity assists will take a lot of time, as you spend a lot of time waiting for the encounter.

Furthermore, that chart is likely computed via a direct Hohmann transfer, which is one of the most efficient transfer maneuvers available. It also will take a lot longer.

For practical human travel to destinations farther way, you need to perform the so called "star wars maneuver", which is going essentially from A to B in a more or less straight line, which will cost a LOT of delta V.

Re: Suddenly, It Seems, Water Is Everywhere in Solar System

#77

Post by finnh »

coderzach wrote: post #30
Someone1234 wrote: post #20

Earlier quoted context omitted.

That's just a blatant rationalisation because people don't like change. There's nothing natural about understanding either metric or imperial, so suggesting that humans inherently are born with more understanding of one is silly. Metric only wins in my book because it is much easier to convert units (there are no magic numbers for conversion factors). However I'd laugh at anyone who suggest metric is better because p…

> However I'd laugh at anyone who suggest metric is better because people inherently internalise it better I disagree. Once you've been taught a base ten counting system, units that change based on orders of magnitude is very easy to understand. Since almost everyone has a base ten counting system internalized, metric is MUCH easier.

But 12 is evenly divisible in thirds and quarters. Actually pretty useful for a bunch of things. Really it's just too bad we have 10 fingers instead of 12.

Re: Suddenly, It Seems, Water Is Everywhere in Solar System

#79

Post by IndianAstronaut »

Mahn wrote: post #28

Does anyone else think NASA should reconsider their plans for a manned mission to Mars? With Europe, Ceres, Enceladus, Ganymede and many more promising moons out there it seems kind of a waste to spend time, effort and capital in Mars now.

Absolutely. We can learn much more about life in our universe by exploring Europa, Enceladus and Titan. All can be explored for much less than a Mars mission.

Re: Suddenly, It Seems, Water Is Everywhere in Solar System

#80

Post by mitchty »

aguywithamum wrote: post #27
mitchty wrote: post #21

Earlier quoted context omitted.

And? Someone output things in non SI units to something that expected SI. Shit happens. Want me to point to the Beagle probe? Space isn't easy.

The point being that his particular failure could've possibly been avoided if we were not using two parallel measurement systems...

How so? If I build something that doesn't conform to specifications, what does it matter if it happened to be unit conversions? They could have skipped a decimal point and not noticed, because they didn't conform to the specification. More importantly it never got checked or tested or simulated further on up the chain to catch the issue.

Look at the Araine 5. Unit conversions had nothing to do with a computer saying "gimbal an engine 90 degrees".

I'm sorry but this canard of two units being the problem is missing the entire point.

Its an engineering issue and management failure. Just like the space shuttle O rings before them, space is hard. Distilling things down to "america should have used metric cause reasons" is trying to pass off complex problems with bite sized quotes. The only issue is it is wrong.

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