Skimming gas giants

[Vladika]

Actually, that's not true - the garden hose bit. Every summer I buy a free-standing pool for my kids: about 2 1/2 feet deep, enough for them to splash about and cool off in. And, every summer, I end up having to repeatedly clean the thing out. Algae forms on the bottom, dirt gathers from the kids stepping in and out, and so forth. My solution every year is to stick one end of a water hose into the pool, take another end to a convenient end of the yard that's a foot or so lower than the pool bottom, suck hard on that end of the hose and then immediately drop the hose. Water comes up into the hose from my inhalation, and when I drop the hose it coasts down toward the low end of the yard, creating a draw behind it that draws more water into the end of the hose in the pool. Then I go to the pool end of the hose and use that draw to suck up the algae and junk, which ends up pouring out the other end at that low point. It's kind of a trickle, but it seems to be just enough to keep the flow going.

The garden hose is just inflexible enough to put up with that bit of suction without collapsing. I doubt I'm drawing more than a foot or two of water into the hose, but it's enough to get the water past the lip of the pool and on its way downward, and then that downward pull does the rest of the job for me. I suspect you're right that if I had some real suction, the hose would collapse, but I can't put out that kind of power with my lungs. The little bit of power I can apply is just enough to get the job started without exceeding the hose's strength. As long as you don't exceed a certain level of suction, the hose acts as a pipe.

Try it the other way around as challenged. You are siphoning here, and that's a very different thing. You are correct in that it is acting as a pipe in your last sentence.

Lay on the bottom of that pool and try to suck air. Isn't going to happen. In all fairness, you couldn't do it with a pipe long enough to reach the surface either.

Quick cheesy physics: At two feet of depth you are looking at about 1 psi over your entire rib cage. You can't inflate your lungs at that depth. Your chest muscles just won't function. (It was sort of a trick/cheat, but an interesting one I hope.)

 

[HG_B]

Now, again, I'm not good at physics past a certain fairly basic point, but I don't see 99% efficiency in those numbers. Maybe someone can show me where I'm not understanding this right.

You have no idea what the efficiency is. There is no game data on how much emitted power it takes to create an artificial grav field that will move x mass at x acceleration. So, you can calculate until doomsday and still not have an answer...

 

[HG_B]

Dad had to setup a special dirty vacuum chamber for testing the LRO instrument used to confirm water on the moon. Technically no where near an 'absolute vacuum'.

Irrelevant to my point. Keep studying though.

 

[aramis]

Another thing, you can't suck through a hose. A pipe yes, a hose no.

The large nearly ridge black "hose" lengths you see on firetrucks are in fact short, nearly rigid and are actually "pipes".

However, if you think you can suck through a hose, give it a try. Lay down (or stand up) with your mouth on a length of garden hose about 2 feet below the surface of a pool. Suck till you asphyxiate, pass out, or have a heart attack, but you aren't going to suck air. (You can't do this with a rigid pipe either. Don't believe it? Try it.)

Or, try sucking water through a long flexible hose. It will collapse in both of the given cases. (In either case pumping works just fine.)

Depends on the type of hose. A flat folding fire hose, you're quite correct.

A typical garden hose is up to 50' long, semi rigid, and as long as you don't exceed a rise of 5' above water level, you can start the siphon by suction. This is how one usually empties a waterbed.

And, at 5' under the water level, I've inhaled air from a garden hose... in through the hose, out through the nose. It's called Snorkeling.

 

[Carlobrand]

Try it the other way around as challenged. ...

Try it the ... oh, you're in the pool! Wait, is two feet enough? My kids do that all the time with their toys, resting on the bottom playing super spy hiding in the reeds, but the pool's like 2 1/2 feet, so I'm not sure there's actually two feet of water above them.

But, I thought you were also talking about, "sucking water through a long flexible hose."

 

[Vladika]

Depends on the type of hose. A flat folding fire hose, you're quite correct.

A typical garden hose is up to 50' long, semi rigid, and as long as you don't exceed a rise of 5' above water level, you can start the siphon by suction. This is how one usually empties a waterbed.

And, at 5' under the water level, I've inhaled air from a garden hose... in through the hose, out through the nose. It's called Snorkeling.

I doubt that.

https://en.wikipedia.org/wiki/Snorkeling

The optimum design length of the snorkel tube is at most 40 centimetres (about 16 inches). A longer tube would not allow breathing when snorkelling deeper, since it would place the lungs in deeper water where the surrounding water pressure is higher. The lungs would then be unable to inflate when the snorkeler inhales, because the muscles that expand the lungs are not strong enough to operate against the higher pressure.

You are saying you did this at 5 feet submerged? That's roughly 2.5 psi. A 10 inch by 10 inch area on your chest would be 100 square inches and 250 lbs. Can we try a 36 inch chest around and 15 inches deep from top to bottom of lungs? That is 1350 lbs.

Never happened and never will.

 

[Carlobrand]

You have no idea what the efficiency is. There is no game data on how much emitted power it takes to create an artificial grav field that will move x mass at x acceleration. So, you can calculate until doomsday and still not have an answer...

Or, I can have you or someone else explain why the physics doesn't make sense to my inadequately trained mind in this case. Power go in, effect come out, matter/energy can neither be created nor destroyed and all that stuff. Either I am not understanding the numbers - which is quite possible, I do regulations for a living, not physics - or there's a big whopping difference between the power being applied to the job and the work that results, and saying "no game data" neither changes that nor improves my meager understanding of physics.

You're better off speculating that the missing power's all turning uselessly into neutrinos than trying to argue that things don't need to balance because there's no game data on what happens between A and B. The physics gods decree that the scales must balance - that is one of the very few things I do know for certain.

 

[Carlobrand]

I doubt that.

https://en.wikipedia.org/wiki/Snorkeling

​

You are saying you did this at 5 feet submerged? That's roughly 2.5 psi. A 10 inch by 10 inch area on your chest would be 100 square inches and 250 lbs. Can we try a 36 inch chest around and 15 inches deep from top to bottom of lungs? That is 1350 lbs.

Never happened and never will.

The link isn't functioning right. I get an http://https:// instead of an https://, which is prompting my IE to say it can't connect. I'm having to cut and paste the link to make it work.

Here's a University of Sydney physics link that says 200 mm (about 8 inches) is about as long as a snorkel can be and be effective, due to pressure around the chest.

http://www.physics.usyd.edu.au/teach_res/jp/fluids/pressure3.pdf

Most of the scuba/snorkel sites are saying anything from two to three feet is absolute max for a snorkel, with most people not able to draw breath at all at two. Beyond that they're using something they're calling a hookah, which apparently involves a snorkel with a compressor and a regulator. One guy on one site claims to be working toward seven feet with a snorkel, but everyone else there is skeptical.

Interesting, two feet's only about a pound over regular pressure - 1.06 atmospheres. My kids, I think I'll take a tape measure and see how they're doing it.

 

[Blue Ghost]

Getting back to the topic at hand;

Dangers of Jovian body refueling;
Massive EMF; ship's hull/shielding protects occupants
Radiation caught in EMF; ship's hull/shielding protects occupants
Gas Giant gravity; parabolic course at full burn
Lightening strike; unlikely at parabolic altitudes. and Jupiter strength lightening isn't going to effect the hull.
Lower altitudes; not possible because your manuevre drive can't keep you aloft even combined with grav drive assist.

As I understand it, those are the issues at present as per the strict interpretation of the rules.

Back in the day, IMTU;
Massive EMF; we didn't know, or saw it briefly mentioned on NOVA or something...not an issue.
Radiation in EMF; ditto, it's outer space, we had no idea; ergo ignored.
Gravity; we knew about the tremendous pulls, but always thought the grav drives in all Traveller vehicles worked against gravity wells of all sorts, but no, no one ever tried cruising through a gas giant in an air raft or grav belt...though it would be interesting.
Lightening Strikes; it never came up.
Lower Altitudes in gas giants; ditto, it never came up, the guys would say "is there a gas giant nearby? Let's go fill her up."

The same went with water worlds. Other gaming groups were a little more strident in adherence to superficialities like the possibility of misjumping because there's a bunch of O atoms mixed in with the H. But gas giant "exploration" so to speak, never was an issue for anyone.

The ammonia ice at upper altitudes was also a non issue for even the most technical and scientifically savvy of the gamers I played with. I'm guessing a lot of them simply weren't astronomers because refuelling at a gas giant, to me and them at least, meant flying through clouds with scoops open. Suck down some ammonia air (because it is air, just very poisonous air to humans), and let the ship's power plant do her thing.

Thanks all

I'm going to start a new thread about Ice Refuelling; ice harvesting, water harvesting, etc.

 

[Vladika]

OK I went back and think I fixed it. Thanks.

Try "hookah diving". It uses a compressor on the surface, most often floating in/on a ring buoy. This pumps the air down to the diver.

 

[Blue Ghost]

Okay, help me out here, I'm not a physicist. EMF = Electromagnetic field, yes? Ergo EM field. We have MRIs here on Earth that produce some whopping massive fields, no? Are we talking about the jovian EM fields themselves, or the radiation resulting from charged particles that become trapped in those fields?

Sorry Carlobrand, I never did answer this, but we did address it, but yes, to clarify, it was the actual EMF field and not just the radiation that I was asking about. The field itself is said to be so intense as to kill anyone entering it. The radiation that's trapped in it is a different issue, but yes, that too, by itself, is said to be lethal. But apparently Traveller starship hulls can deal with both.

 

[HG_B]

Either I am not understanding the numbers - which is quite possible, I do regulations for a living, not physics - or there's a big whopping difference between the power being applied to the job and the work that results, and saying "no game data" neither changes that nor improves my meager understanding of physics.
.

Study Efficiency. As I stated, the numbers are meaningless as you have no baseline number. What is a theoretical 100% efficient Grav M-Drive numbers for energy needed at the end of process to create a certain strength grav field? Pretty simple concept. I can't make it any simpler.

Example: You have a generator on your vehicle that can produce 1Mw at full output. You have an grav drive used to move your vehicle that requires 500Kw to produce 1G of acceleration.

Q: How efficient is your Grav drive?

A: You have no idea because we don't know how much energy coming out of the "grav emitters" (the last step of the G-drive) it requires to produce that grav field..

 

[Carlobrand]

...You have an grav drive used to move your vehicle that requires 500Kw to produce 1G of acceleration.

Q: How efficient is your Grav drive?...

You have energy going in. You have work resulting. How much of the energy going in is producing useful work (1G acceleration)? How much is not?

One thing my physics teacher did manage to drill into me - admittedly with some effort - was that if the two sides of the equation did not balance, there was a mistake. Figuring out what precisely the mistake was, that was where I ran into problems and why to my everlasting shame my career as a physics major didn't survive more than a year at college. However, if it does not balance, there is a mistake - energy cannot just disappear into the aether.

The details of what happens with that portion of energy that is not producing useful work - whether it's lost as heat, converted into other particles in the course of producing whatever it is that's simulating gravity, converting into a blast of radio waves or light or some phenomenon akin to Cherenkov radiation, whatever - that can be whatever we want it to be since it's all describing phenomena that, to my knowledge, is unknown to modern science. In other words, we simply don't know what is needed to produce a whatever-it-is-that-counters-gravity and what "waste" particles or energies would be produced as a result, any more than we know what is needed to produce a black globe or a nuclear damper field. We are utterly free to decide that it produces waste heat, neutrinos, visible light, x-rays, or any other energetic product that suits the story we want to tell - so long as we make sure the equations balance.

 

[HG_B]

You have energy going in. You have work resulting. How much of the energy going in is producing useful work (1G acceleration)? How much is not?

<snip>

Exactly. The game rules don't tell us. So, the M-drive could be 1% efficient or 99%. We just don't know from the info provided.

 

[Ishmael]

With rules that actually use mass in determining performance, such as MT or TNE, knowing that mass and acceleration can give us work. In the absence of such rules, a common rule-of-thumb ( iirc ) is to assume 1 dton masses 10 tonnes.


So depending on the ruleset of choice, the info is available indirectly.

 

[HG_B]

So depending on the ruleset of choice, the info is available indirectly.

Nope. (How much work could be done by an ideal M-drive using X amount of energy?)

 

[Ishmael]

well....
a 100 dton ship has a mass of 1000 tonnes ( depending on which rule-of-thumb you use...TNE gives a dton as massing 10 tonnes, iirc ). or 1,000,000 kg

at 1 g, it adds 10 m/s velocity each second.
E=.5*mass*v^2 give a total added KE of 50,000,000 joules each second ( joule per second = watt )

thus, a 100 dton ship will need 50 Mw at 100% efficiency to accelerate at 1g

How much energy does an m-drive from need a power plant to do this?
you can get efficiency with that info.

I'm not sure Traveller rules can survive this sort of thing though. I understand that it can lead to some odd numbers and perpetual motion machines.

If I'm wrong, I'm sure someone will point out any errors.

 

[HG_B]

thus, a 100 dton ship will need 50 Mw at 100% efficiency to accelerate at 1g

You still haven't supplied the missing data. See below.

 

[Blue Ghost]

HG_B; I'm curious if there's some issue with the rules that's not gybing with your knowledge about work and power. Is it simply the unknown efficiency of Traveller starship; drives, power plant and what not?

Or, simply put, is there something else that's an issue here?

 

[HG_B]

HG_B; I'm curious if there's some issue with the rules that's not gybing with your knowledge about work and power.

The rules don't give the needed data to determine efficiency of grav drives. Even Einstein wouldn't be able to work the problem. It's only a problem if one is trying to determine it. Like below when one was trying to determine waste heat available from a drive to produce additional thrust from heated air.