Floaters – Onward to Mars etc

Floaters – Onward to Mars etc

In an earlier exchange I convinced myself that a dirigible on Mars was simply not practical. The issue is the low atmospheric density. It is much easier to design something to float in a dense medium. You and I can swim quite easily in water, but have difficulty flying, well, I do anyway.

The reason I am in favour of gas balloons is that once they are in flight they do not need energy to maintain them there. That makes them economical. This does not rule out hot-air (or other gas) balloons or gliders but they are issues for another day.

I don’t give up easily, and I thought I would investigate the possibility of using balloons on other bodies.

Bodies I investigated briefly and rejected:

Body:            Atmospheric Density:    Composition:

Mercury        “tenuous”                        -

Mars            0.02 kg/m3                        95% CO2

Ganymede    “micro pascals”                -

Europa           “tenuous”                        -

Jupiter            90% Hydrogen.             “Hydrogen and Helium in roughly solar proportions”

All the data is sourced from Wikipedia or other basic websites because I’m lazy.

Balloons are favoured by dense atmosphere composed of gases with a high molecular weight. Low gravity helps too.

Balloons are not practical on Mercury, Mars, Europa or Ganymede because of the low atmospheric density.

Jupiter is an interesting case. The atmosphere is so deep that there will be a wide range of density. The composition being mostly hydrogen means that something relying on pure “gas buoyancy” will not work (because you can’t get less dense that Hydrogen). On the other hand, the pressures are so high that the penalty for solids is less. Jupiter needs its own special, radical approach. Jupiter is not really rejected, but it needs a completely different approach.

Venus

On the other hand, gas balloons may have real potential on Venus!

Surface Temperature:    464 deg C

Pressure:                        92 Bar

Gravity:                          8.87 m/s2, 0.904 g

Atmospheric Density:    65 kg/m3

Composition:                  96.5%

If we assume ideal gas laws apply and the Venusian atmosphere is entirely CO2, then the density of a gas is simply going to in ratio to the molecular weight of the gas relative to CO2 (the other conditions, temperature and pressure remain constant).

This gives us the following:

Density of Atmosphere:                                65 kg/m3

Lift from 1m3 of vacuum:                            65 kg

Density of H2 at same conditions (2/44)      2.95 kg/m3

Lift from 1m3 of H2 at same conditions.      62 kg

Density of He at same conditions (4/44):      5.91 kg/m3

Lift from 1m3 of He at same conditions:       59.1 kg

There you are! If my sums are mostly right, that means that the high pressure and CO2 atmosphere means that on Venus 1 m3 of enclosed Hydrogen can lift 62 kg of load.

The Venusian atmosphere contains Sulphuric Acid. I would propose manufacturing hydrogen “in situ”. Possible routes are: bringing a reactive metal like lithium with you and reacting it with sulphuric acid, or breaking down the acid with energy. Suddenly making this practical becomes a materials-science problem.

Next Steps:

I prefer “back of a beer-mat” to “back of a fag packet” but that exercise convinces me that balloons are worth investigating for Venus. Next stage would be “back of an envelope”.

Do you know anything about aerodynamics and lift? (because I don’t). Are you aware of any equations I could use in a similar way to screen glider devices for different bodies?

I think gliders will be impractical on Mercury/Europa/Ganymede because of the low atmospheric density. I think they will probably either have to move far too fast or be vast. I’d like to do the sums for Mars (just to “show it won’t work”).

On the other hand, hot-“air” balloons and gliders (or “fish”) might be really interesting for Jupiter, but I’m still working out where to start. Any suggestions?

(Original 5th June 2021)

Drain problem in Cork City - Titan, Ceres and Dwarf planets

 Hi, Yes I though the Titan thing was good. As for the moons… well, it’s understandable. Our generation called Pluto a planet – the category of dwarf planets didn’t exist then, and all those moons are simply too much to remember. 

Titan is one of several places which look well worth investigating. In a perverse way, all these moons and some of the dwarf planets: Ceres and even Pluto, may make better targets for human occupation than planets. They are deep space but with a surface and no gravity well. https://en.wikipedia.org/wiki/Ceres_(dwarf_planet) Actually, the Solar System is looking more interesting than it has, but not in the ways or in the places we expected.

And… it hasn’t been a good week for me, and though I’m through it ok, I may be distracted suddenly for a while. 

On Wednesday evening, Noreen got a phone call from Margaret to say “there’s sewage in the yard” of our cottage down in Cork City. A photo was enough to confirm the issue and in the time it took to collect a few tools (overalls, gloves, drain rods…) and a change of clothing I was on my way (40 miles to Cork City). 

By 01:30 I had the mess cleared and had established that while the loo and shower-room drains were working satisfactorily, the gulley for the kitchen (which was the source of the effluent), was blocked. There had been things in that effluent which had not come direct from any kitchen and certainly not ours, including an almost complete sausage! No, I do not know what variety; it was like a length of garlic sausage with a reddish skin. The mess cleared up and it being possible to use the loo (but not the kitchen sink) I washed and went to bed.  

The following morning, Noreen (who fortunately is on vacation from school) was down at 09:00. While I started trying to clear the blockage, Noreen started on the internet and phone. In not so short order she went through: Irish Water, Cork City Council, 2 drains companies and even the Gardai (police, because we needed to get access to the house next door). Everybody was very helpful, but there were issues all along the way. Meanwhile, I bailed and “plunged” and groped.

By a miracle, “plunging”, persistence, groping in the darkness and with the use of chemicals, there was water movement by about 15:00 and by 16:00 I had the gulley draining in a satisfactory way. We had managed to resolve the immediate crisis for about EUR 30 on parking, EUR 20 on drain cleaner and whatever we spend on petrol. After I’d demonstrated the results, I washed up, we all shared some tea and a bun, and Noreen and Margaret went home, while I remained, to enjoy a TV dinner and a single can of strong cider. I went to bed early and I slept like a log.

The following day, I did a survey of my drains and the area. Compared to the previous night I felt amazingly relaxed. In the early afternoon I had a visit from someone from our preferred drains company. The bloke explained that we had two issues: 1) No rodding/jetting access and 2) No vent to relieve pressure from the sewer. The solution is going to have to be removing the loo pan and using the access into the sewer for inspection with an endoscope and then digging up the yard (guided by  the endoscope results), and then jetting and fitting a small inspection chamber. Really what is behind all this, is that I have a house which is over a hundred years old and the foul drainage has developed by a process of accretion.

I’ve fixed the immediate crisis, but now I have to take control of the project (because that is what it has become). Of course, the screws holding down the pan are badly rusted. I’m going to investigate removing the bowl but I’m reconciled to hiring a plumber and I know that the usual solution in these cases is to break the bowl – it’s easier and cheaper. If I get someone else to do the work, I will get them to fit easily removable screws and a service valve on the cistern at the same time (to save the need for draining the cold water tank in the future).

I’ve now got an excruciatingly large scale map (stolen from the Irish Gas website) of the relevant houses, and the results of my survey. Tomorrow evening I will investigate the loo pan and then we will move on from there. 

I may be busy for a few days…

Cheers, 

Tom

Trying to stay out of the brown. Onward to Mars, or Titan!   

(Originally posted 17th June 2021)

From: pink582 [mailto:pink582@btinternet.com] 

Sent: 10 June 2021 10:54

To: Tom Gillies

Subject: Re: Titan

Hello Tom,

thanks for doc about Titan, I may watch others in the series. When it comes to the moons I get a bit hazy....when there were only a handful of moons knowing their names seem to make sense but when you get 53 confirmed moons plus 29 other likely candidates....well I lost the plot.

two things did come out of the doc for me...1) the magnetic field of Saturn itself is strong enough to protect the atm of Titan from solar wind for 90% of the time...I also guess the solar wind is less dense out there.

2) very thick atm...if you want a fast trip to Saturn slowing down won't be so difficult...reference ballute idea in 2010 movie.....may be you could rig a past both through Saturn and Titan.

All the best

Jeff

------ Original Message ------

From: "Tom Gillies" <gillies.tom@googlemail.com>

To: "Jeff Pink" <pink582@btinternet.com>

Sent: Wednesday, 9 Jun, 2021 At 19:32

Subject: Titan 

I’m sure you will be interested in this, and I’m going to check some figures tomorrow

https://www.youtube.com/watch?v=qGy4uyHVUYA 

Regards,

Tom 

Flying not Floating

 

Flying not Floating

The simplest formula for calculating lift that I can find is:

 ρ v² S C_L

Where:

·         L is the lift force

·         ρ is the fluid density – originally of “air”

·         v is the velocity or “true airspeed”

·         S is the planform (projected) wing area

·         C_L is the lift coefficient at the desired angle of attack, Mach Number and Reynolds Number

https://en.wikipedia.org/wiki/Lift_(force)

(The representation of the equation got mangled and I can't be bothered to fix it)

Typical value of C_L lift coefficient is 1.5

https://www.sciencedirect.com/topics/engineering/lift-coefficient

If I assume that I want Lift force equal to the downward force, then that means the Lift I require is (Mass * local Gravity).

Do some algebra and rearrange the equation to get (looks like super and sub-scripts don’t work properly in equations with fractions):

The first term is a constant for the body in question, the second term is the inverse of the density and the third term is the inverse square of the “airspeed” velocity. Everything varies as you would expect.

Physical Properties on various bodies:

Body:	Gravity (m/s2)	Atm Density (kg/m3):	Lift for 1 kg (N):	Temp (deg C):	Atm Pressure (Bar):	Notes:
Venus	8.87	65	8.87	464	92
Earth (Air)	9.81	1.2	9.81	20	1	*
Earth (Water)	9.81	1000	9.81	20	1	*
Mars	3.72	0.020	3.72	-63	0.06
Jupiter	24.8	1.2	24.8	-70	10	*
Saturn	10.44	1.2	10.44	-139	1	*
Titan	1.35	53	1.35	-179	1.5

 

Notes:

(*)          Atmospheric density on a gas giant can be anything you choose it to be, depending on altitude/depth.

Calculate the “factor” for all the different bodies

Body:	L/CL:	Inverse Density:	“Factor”:
Venus	5.91	0.154	0.910
Earth (Air)	6.54	0.83
Earth (Water)	6.54	0.001
Mars	2.48	50
Jupiter	16.53	0.83
Saturn	6.96	0.83
Titan	0.90	0.94

 

 (Originally 17th July 2021)

Gateways and Boundaries

Do you like mysterious doors or gateways, maybe even to ways to other dimensions? Of course you do, everybody does! Here's a little tale for you. Of course it's all true, but maybe the contrast and brilliance have been turned up to eleven in places.

When you were in K???? I remember taking you along the road and through a field to go and look at the River A????, which flows down from F???? village to where the river joins the larger River D???? in K???? town. 

Every year, when I cut the hedge which forms the boundary of my place, I have to trek along the road and then back through the field, so I can inspect and cut the back of my own hedge. It's all a bit of a nuisance. The hedge itself is Leylandii and somewhere inside of that is a chain-link fence supported on concrete posts. As I'm sure someone must have said, sometime, "it ain't going anywhere". Fortunately, I took the growing heads off the plants shortly after we moved in, so it’s not going to get out of control. Now I wish that the people who built the house had used something other than Leylandii, because it's too vigorous, but I'm not complaining because it’s attractive and maintenance free apart from once a year. 

Last year, I cut the inside and top of the hedge and had got to the stage of thinking about going round to the back. Cutting my hedge takes several days, so the job can spread over weeks. For some reason, I cut a little deeper into the hedge than I do usually in one back corner, and I noticed that the hedge growth was a little less dense there than normal. I poked around a bit more and found that the posts for the chain-link fence had been arranged in such a way that they formed a gateway inside the hedge.

This potential gateway was intriguing, so I showed it to Noreen and said that I thought it would be practical to make a gateway out into the field. The effort of creating the gateway would make the exercise of cutting the back of the hedge a whole lot simpler for the current  year and all future years (no need to walk a hundred yards along a busy road and back through the field). Noreen agreed, and a day or so later I had a gateway. 

I think the background story of my gateway is that when my house was being built, the builders constructed the gateway for access. They even put a threshold sill stone in place. When they were finished with the house, the builders filled the gap with an separate bit of fencing and planted the hedge, which over time obscured the potential gap.

A little more work, and I had constructed a little wicket gate to fit the gap. I can even point to evidence of the gate being completed on 25th August last year. Gate construction was made easier by having square upright concrete posts to work to. Not only is the gate easy to open and close, but it is invisible from both my garden and from the field! From my garden it is camouflaged by a piece of trellis covered by plastic pretend hedge, and from the other direction it exits into a wooded field boundary and is invisible from the field itself. So, now I had a hidden, secure gateway between my garden and the field beyond. It’s the sort of thing children love (and that includes children of advancing years).

The gateway served its intended purpose in simplifying the maintenance of my hedge, but it gave more. Now I have the gateway, I'm in the habit of walking down to the river, typically once a week. The distance is 150 metres as the crow flies or 350 metres around the perimeter of the field (which is the way I go, 'cos I'm good). 

Nobody would describe my place as urban and to call it suburban would be a positive insult, but access to the river takes rural to a new level. All you can hear on the other side of the hedge are natural sounds and the gentle whispering of traffic on the distant road. 

It really is peaceful down by the river. Having access to the river is a great improvement to my amenities.  Come the summer, I may spend a bit more time down there. My neighbours don't mind (because they walk their dogs down by the river), and I don't think the person farming the field will ever know!

When I’m walking around the field something strange happens. The atmosphere changes and everything becomes much quieter. The sounds of traffic from the road cease completely. This always happens in the same place. The effect does not change with the weather, in sunshine or drizzle, the same peace descends. The silence is welcoming, waiting to be filled by the sounds of the river. 

When I reach the river the banks are clothed by mature native trees and beyond the margin on the far bank there is a dark plantation of commercial conifers. Upstream there is short length of rapids and downstream the river broadens and becomes much quieter. On the opposite bank a tree trails a dead limb into the water. When the river is high this branch is dragged forward with the current and flicks back when the tension overcomes the water. The motion is repeated rhythmically. The atmosphere is quiet except for the sound of water, no houses are visible, not even my own, which is only 150 metres away. I am in another dimension, separate to, and completely insulated from, the modern world. Every time I go there I pass through a hidden portal and traverse a zone of silence and when I return the experience is reversed.

I’m afraid there is a prosaic explanation to my inter-dimensional portal. The field has an uneven slope between my house and the river. The steeper slope in the middle means that when I'm at the river the houses are hidden and all the sound from the road passes above my head. Whatever you may think, unnaturally, I choose to ignore the obvious and continue to visit my magical realm via a hidden gateway and barrier of silence.

4th February 2023