A reason to dive into Jool

[Spricigo]

Not a bad idea, but there is already a reason to dive into Jool: the challenge.

[SnailsAttack]

On 1/26/2018 at 4:23 PM, Spricigo said:

Not a bad idea, but there is already a reason to dive into Jool: the challenge.

Whats the challenge to it? It's not like a suicide mission into Jool is all that difficult.

[Spricigo]

24 minutes ago, SnailsAttack said:

Whats the challenge to it? It's not like a suicide mission into Jool is all that difficult.

how about trying to do as low as possible and still return?

[Clockwork13]

On 2/28/2016 at 7:33 AM, cubinator said:

Good idea. Another interesting thing would be to have balloon parts that would allow a probe to float around in Jool for a prolonged period of time, kind of like a lander can stay on a planet for a long time before breaking/becoming obsolete. Of course, a balloon probe probably wouldn't last nearly as long as a planetary lander, but it would be enough to get science from different altitudes.

The problem that I've noticed with balloons is that it's considered atmospheric flight so you're forced either to wait out the mission or revert

[Spricigo]

1 minute ago, Clockwork13 said:

The problem that I've noticed with balloons is that it's considered atmospheric flight so you're forced either to wait out the mission or revert

there is the airpark mod. 

[septemberWaves]

On 3/6/2016 at 1:19 PM, Snark said:

So... not happening anytime soon, I'd wager.

I think you're thinking too small. Sure, a one-meter vacuum-filled sphere is definitely not likely to be able to withstand the pressure of a mostly-hydrogen atmosphere, but volume scales quicker than area. So the bigger you build a balloon, the more you can reinforce it against the pressure because it'll have increasingly-high lifting capabilities compared to the pressure it has to withstand. Make a big enough balloon and you could build the whole thing out of a high-strength rigid metal and still have it capable of supporting a fairly huge payload in a gas giant's atmosphere. The issue then would be defending it from atmospheric storms rather than keeping the pressure from crushing it.

It's definitely impractical and unlikely, but so is just about everything in KSP.

Edited January 29, 2018 by eloquentJane

[Guest]

Great idea. Warmly seconded!

A minimal implementation ought to be pretty simple, too. I'd settle for a few atmospheric layers and the occasional floaty anomaly to discover. Anything beyond that is chrome.

[Snark]

6 hours ago, eloquentJane said:

I think you're thinking too small.

Response in spoiler section, because this is really getting off-topic for the thread (which is about airships in KSP)-- talk about the actual physical realities involved is more of a "Science & Spaceflight" topic, so perhaps further discussion on that matter would be better taken up there.    The TL;DR is "no, this is not the case, and I stand by my earlier statement."

Spoiler

6 hours ago, eloquentJane said:

Sure, a one-meter vacuum-filled sphere is definitely not likely to be able to withstand the pressure of a mostly-hydrogen atmosphere, but volume scales quicker than area. So the bigger you build a balloon, the more you can reinforce it against the pressure because it'll have increasingly-high lifting capabilities compared to the pressure it has to withstand.

Unfortunately, the exact opposite is true.  The bigger you build a vacuum balloon, the worse the problem gets.  The square-cube law is working against you.

Yes, it's true that a balloon of the same thickness that's twice the diameter would have eight times the volume (and therefore buoyancy), but only four times the area (and therefore mass), so that's a good thing, right?

Except that it doesn't work that way if you're trying to build a vacuum balloon.  Because the thickness can't be the same.  Because the bigger the structure, the more structural reinforcing it requires, and the strength requirement scales up nonlinearly.

Making a big pressure-withstanding vessel is harder than making a small pressure-withstanding vessel.  It's the physics behind the engineering reasons why, for example, bathyscaphes tend to be claustrophobically small and cramped: they have to be made as small as possible to give the walls the best mechanical strength for withstanding the pressure.  Take a look at these images of the Trieste:

There's a good reason why the actual pressure vessel is a tiny, cramped sphere that's made as small as it can possibly be while still holding a human in it, instead of making the whole vessel be a nice big roomy buoyant sphere:  it's because a big sphere would be crushed, but a small sphere can be strong enough to stay intact.

(If we ever do succeed in engineering a material that's light and strong enough to be able to generate "vacuum buoyancy", we won't be seeing "giant monolithic sphere" airships-- much more likely would be a ship with a big bag of tiny individually buoyant spheres.)

The problem is... we don't have any such material currently available.  A vacuum balloon would be a tremendously useful accomplishment-- if we could do this now, we would already be doing it.  We simply don't have the engineering for it.  It's a really hard problem, because gases have a very, very high ratio of pressure to density, and it gets even uglier if the gas in question has a very low molecular mass, as is the case with a gas giant's atmosphere.

We can't do it yet even in Earth's atmosphere-- which is the easy case, compared with a gas giant, because our atmosphere's average molecular mass is over 14 times higher than a gas giant's.  To make a vacuum balloon on a gas giant, we'd need a material over 14 times stronger than what we'd need for our own atmosphere; and we haven't even done it here yet.

Please note that I didn't say "impossible".  I simply said that it would require science-fictional materials that we don't currently have and do not appear imminently able to do:

On 3/6/2016 at 5:19 AM, Snark said:

It's a fine idea for science fiction.    However, unless you're willing to posit ultra-strong materials, nanotech, or the like, it's simply not possible in reality (at least not with technology that we currently have, or are likely to in the near future).

You'll also note that I didn't say "never." I said,

On 3/6/2016 at 5:19 AM, Snark said:

not happening anytime soon, I'd wager

It's also worth noting that none of this has anything to do with the actual topic of the thread, which is having airships in KSP.  There are plenty of atmospheres in KSP where I could plausibly imagine an airship working, even a "traditional" one filled with helium or something.  I could even imagine an airship working on a gas giant such as Jool, if one imagines some power source that enables a hot-air balloon.

I'm just saying that a vacuum balloon is "science-fictional" materials science and engineering right now-- I haven't seen any serious proposal even on the drawing boards of NASA or anywhere else, because it's simply not in the foreseeable near future.

Of course, whether KSP should have science-fictional stuff (like hyperstrong materials, or warp drives, or whatever else one wants to postulate) is a matter of subjective taste-- there's no objective "right answer" to that.  Personally, I prefer that it try to stay at least notionally "real", i.e. technologies that are reasonably plausible (current or near-future engineering), perhaps tweaked for playability (such as what they've done with ion drives)-- and leave the sci-fi stuff to mods.  But that's just my own personal preference, and of course other folks will have their own opinions on the matter.

 

[septemberWaves]

4 hours ago, Snark said:

if one imagines some power source that enables a hot-air balloon

Need a good source of heat that's long-lasting and doesn't require large amounts of combustible fuel? We already have one. Of course, the radioactivity would make it impractical for a crewed vessel, as would the amount of plutonium needed to keep a significant mass floating I suspect, but still. Anyway, I'll stop derailing the thread now.

[Guest]

15 hours ago, eloquentJane said:

the amount of plutonium needed to keep a significant mass floating

...is a few kilos at most. The critical mass for Pu-238 is around 10 kg, and as you approach it, it will get progressively hotter. Reactors run at core temperatures of around 1000 degrees C. An unshielded reactor with minimal controllability would not be all that big either, it's a pretty simple device really.

An atomic-powered hot-air balloon would be completely feasible, if you don't mind the radiation and are willing to dispense with pesky safety mechanisms preventing accidental meltdowns anyway.

Edit: I got curious and looked some stuff up. Nuclear reactors (not just RTGs) have been used in space. The reactor mass has ranged from a bit over 200 kg to a bit over 1 ton, for thermal power outputs ranging from 40 kW to 2 MW or so. A 40 kW reactor ought to keep a pret-ty big balloon nice and hot.

Edited January 30, 2018 by Guest

[Laie]

I'm with @Spricigo on this one: I didn't need no juicy science to lure me into Jool's depths, sheer curiosity was enough. Having done it, once, I'm utterly satisfied and actually glad that there's no reason why I'm "supposed" to do it.

[septemberWaves]

@Brikoleur I was thinking more along the lines of how an RTG works than a reactor. A reactor would deplete the plutonium much quicker; you'd be better off and safer avoiding a chain reaction and just using the heat of its natural decay. And I know that you can get a lot of heat from a small amount of plutonium, but that particular isotope of plutonium is extremely hard to obtain in significant quantities; I didn't mean the mass would be inconvenient to transport, but that it would likely be inconvenient (and therefore expensive) to obtain in the first place.

[Guest]

What, you mean not everything that works in KSP works in real life?

[sevenperforce]

How hard would it be to add Joolian "storms" which are essentially supposed to represent gigantic hurricanes filled with updrafts, but are locally implemented as a significant decrease in local gravity, perhaps with additional science via atmospheric sampling? Dive into one of those, and you can get pretty deep without getting crushed, and still have enough dV to get back out since the "updrafts" are lifting you (though really it would just be a region of lower gravity in-game).

Shouldn't be too hard to write. 

[Spricigo]

3 hours ago, sevenperforce said:

Shouldn't be too hard to write. 

If I had a feature for each time I read that...

 

 

[sevenperforce]

51 minutes ago, Spricigo said:

4 hours ago, sevenperforce said:

Shouldn't be too hard to write. 

If I had a feature for each time I read that...

....compared to more complex things.

[FleshJeb]

On 1/29/2018 at 1:00 PM, eloquentJane said:

Need a good source of heat that's long-lasting and doesn't require large amounts of combustible fuel? We already have one. Of course, the radioactivity would make it impractical for a crewed vessel, as would the amount of plutonium needed to keep a significant mass floating I suspect, but still. Anyway, I'll stop derailing the thread now.

If you're going to go that far, you might as well do this: https://en.wikipedia.org/wiki/Project_Pluto and cruise around the atmosphere on wings

[Gordon Fecyk]

I saw this thread, remembered Snark's project, and thought, why not bring it up to date.

https://github.com/gordonfpanam/JoolBiomes/releases

I left a pull request, but please try it out in the meantime.

If you also have Stock Visual Enhancements, the Great Green Spot won't line up with the clouds in that band unless you also modify the rotation rate of that cloud texture. Edit SVE_Clouds.cfg:

	OBJECT
	{
		name = Jool-Bands2
		body = Jool
		speed = 0,-1000,0
		altitude = 10
		offset = 178,0,-2

Hm, I remember setting the speed to 0,0,0 in the EVE Clouds editor. It must use -1000 to represent zero as well.