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do you have a hobby? if so, what is it?

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General interest discussions, not necessarily related to depletion.
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Unread postby Jenab6 » Sun 04 Jun 2006, 12:18:08

$this->bbcode_second_pass_quote('ravensburg', 'O')h man I am going to get some crap for this but ok,
One of my hobbies is going up 4x4 in the mountains by where I live.
The old jeep likes to suck down a lot of gas and for most of the year I keep it parked, maybe fill it up once a month. Now I will really get crap for this but so I don’t have to pay to keep that hog running me to work and back I drive a small pink s10 pickup also.

PINK!!! Ha ha ha. :P

My hobby is celestial mechanics. Or anyway it's one of my hobbies. I figured out how to find transfer orbits all by myself!

http://officialprussianblue.net/showthread.php?t=59

I got some help learning the Method of Gauss for determining the oribit of an asteroid from three angle-only positions. But you can tell that I understood what that Russian fellow, A.D. Dubyago, wrote in his book.

http://officialprussianblue.net/showthread.php?t=58

Too bad the energy crisis will put an end to space travel, or I might have gotten a job doing this kind of thing. It's actually pretty fun, sort of like playing pool with rockets and planets, and watching them go where you figured they would.

I play at raising goats, but I don't really make any money off them. They're just pets that I have to keep away from my little apple trees until the trees get bigger.

I'm also growing an orchard: apples, pears, quinces, cherries, peaches, apricots, nectarines, plums, hazelnuts, almonds, walnuts, butternuts, and pecans. I planted nearly all the trees myself, but in 2002 a nice neighbor lady who immigrated here from Bulgaria came over and helped me dig the holes for planting some of the apple trees.

This year, I'm seeing my first fruits. There aren't very many, and only a few of the trees have them. But I'll have some apples from one of my Jonathan trees and from one of my Yellow Newton Pippins. And some pears. And some cherries. And a peach... at least I think it's a peach, but it's still too early to tell. It might be a nectarine. And one of the almond trees is putting out nuts a couple of years sooner than I expected.

Learning how to improvise and make-do is something else I like doing. I'm going to brag about one of my recent triumphs.

Have you ever had the experience of having a dry cistern, no well, and needing to visit the potty? You don't want to use the one indoors, or you'll stink yourself right out of your house. So, at the back of the goat pen, where it's hidden by the wall of the tool shed, there's a toilet that I made from firewood, nails, and a riding lawnmower tire (just the right size) wrapped in duct tape to keep the rubber protrusions from jabbing me on the backside. The seat's about two feet off the ground. It's held up by four hickory log sections, each chainsawed about 20" long, which are held together by being nailed to split sections of other lumber. Between the logs and below the seat is the "evidence bucket."

This hickory is very hard wood. When you try to drive even the thickest, strongest nails into it, the nails nearly always bend. But before that happens, you can usually get them in far enough to hold up several hundred pounds of whatever it is you're nailing to them. Just remember to use the BIG hammer with the HEAVY head, not the claw hammer with the dinky little head.

There's a big nail for hanging the TP where the goat can't get to it, and a separate bucket for holding washing water, and a small shelf by the nail for holding a bar of soap. A shovel is wedged between the wall and an offset waferboard panel; it's for digging holes for burying the evidence at the edge of the woods behind the goat pasture.

Every so often there's a drought and my cistern runs dry. I've done some remedial work to improve my water system, such as installing aluminum screen over the gutters to prevent the spring catkins and the autumn leaves from going through the downspout. I've diverted half the roof washoff through a rainbarrel system of 330 gallons capacity, and when the last barrel is full it overflows into the cistern. So I have an easy, no electric power needed, way to get at my water when the cistern is empty or the electricity is off.

But in a water shortage, you don't want to waste the water you do have by tossing it down the toilet for flushing. You'll need it for cooking and washing, instead. So the outdoor toilet saves several gallons of water each day by handling the "Number Two" body function. (The outdoor urinal is a certain spot where the goat pasture fence goes past a stand of pokeweed. No sense bothering with a bucket for that.)

Jerry Abbott
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Re: do you have a hobby? if so, what is it?

Unread postby Kylon » Sun 04 Jun 2006, 14:43:54

Doing Research, coming up with ideas, reading, studying, learning things. Enlarging my book collection.

Surfing the web.

Fantasizing.

Peak Oil.

Working on projects.

Coming up with solutions to problems, and ideas on how to make money. :)

Typical nerd stuff. :-D
Last edited by Kylon on Wed 07 Jun 2006, 17:53:42, edited 1 time in total.
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Re: do you have a hobby? if so, what is it?

Unread postby SoothSayer » Sun 04 Jun 2006, 14:52:56

figured out how to find transfer orbits all by myself!

I have a couple of books about the space environment etc knocking about ... but have little time to read that sort of thing anymore.
More interested in sociobiology nowadays.

Anyway, although I am a physicist, my pure maths is crap, so I would have used an iterative method of some sort ... maybe even Monte Carlo.

Throw CPU cycles and double precision floats at a problem and it (often) goes away!

I therefore can use a lower order skill than your pure maths to get the same result ... works for me!
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Re: do you have a hobby? if so, what is it?

Unread postby AmericanEmpire » Sun 04 Jun 2006, 15:13:07

Does beating off to porn count as a hobby?
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Re: do you have a hobby? if so, what is it?

Unread postby Zardoz » Sun 04 Jun 2006, 15:17:13

Keeping my 15-year-old son out of trouble.
"Thank you for attending the oil age. We're going to scrape what we can out of these tar pits in Alberta and then shut down the machines and turn out the lights. Goodnight." - seldom_seen
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Re: do you have a hobby? if so, what is it?

Unread postby TheTurtle » Sun 04 Jun 2006, 16:10:02

$this->bbcode_second_pass_quote('killJOY', '')$this->bbcode_second_pass_quote('', 'R')ipping up the forests, eroding the hillsides and disrupting the fauna


Question: where does your house and your furniture and your food come from?

[edit: by which I mean to say, we're all going over the edge, and it's everyone's fault.]


I'm willing to admit that most all of us are caught up in the dominant culture. As such, we are all to blame, if that's the way you want to play it. I would point out that my house purchase was a one time thing and I don't go out into the woods each weekend to cut down trees to expand my house as a way to pass the time. If you don't care to recognize that distinction, that's fine too.

Ravensburg seemed to be looking for some criticism,

$this->bbcode_second_pass_quote('', 'O')h man I am going to get some crap for this but ok,


so I gave him some.

But really I don't care because, as you said, we're all going over the edge ... we are all screwed six different ways from Sunday and there's not really a damned thing we can do about it except learn mental flexibility. Because I'm convinced it's all going to turn out much different (and probably much worse) than most of us imagine.

In the meantime, I'll still try to continue reducing my ecological footprint (just last week I started walking/riding the bus to work, rather than taking my car) ... not because I think it will prevent PO ... just because it's what we all should have been doing all along.

Peace.
“Humankind has not woven the web of life. We are but one thread within it. Whatever we do to the web, we do to ourselves.” (Ted Perry)
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Re: do you have a hobby? if so, what is it?

Unread postby Schweinshaxe » Sun 04 Jun 2006, 16:18:35

$this->bbcode_second_pass_quote('AmericanEmpire', 'D')oes beating off to porn count as a hobby?


You bet it does!

It's a nice little hobby... I try to combine it with my hobby as a power tool collector.
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Unread postby Jenab6 » Mon 05 Jun 2006, 05:16:22

$this->bbcode_second_pass_quote('SoothSayer', '[')b] figured out how to find transfer orbits all by myself!

I have a couple of books about the space environment etc knocking about ... but have little time to read that sort of thing anymore.
More interested in sociobiology nowadays.

Anyway, although I am a physicist, my pure maths is crap, so I would have used an iterative method of some sort ... maybe even Monte Carlo.

Throw CPU cycles and double precision floats at a problem and it (often) goes away!

I therefore can use a lower order skill than your pure maths to get the same result ... works for me!

Open form integration actually sometimes works better than the closed form method I found. It can take account of the gravity of any number of "third bodies" without having to do weird stuff like patching conic sections together. Just use a fast computer so you can keep the time steps small enough. It just takes a long time to crunch all the way through the transfer, and you have to use some kind of homing procedure so that you can find the departure delta-vee, direction and speed, that takes you where you want to be in the amount of time you require for the trip.

You probably realize that in finding transfer orbits the delta-vee is actually the dependent variable. You can pick delta-vees as you will, of course, but what you want to do is locate the correct one, the one that makes your rocket go where you want it to. The "boundary condition" you work under is that your rocket must go from planet A to planet B, and when you choose a time of departure you also choose a position of departure, a position of arrival, and a transit time in the transfer orbit (because the rocket and planet B must reach the same point in space at the same moment). So your independent variable (in practice) is Planet B's position at arrival, and the total time for integration is the transfer orbit's transit time.

Notice that you have to make trials with the dependent variables but the independent variables are fixed? This backwards solving of the problem is what makes things complicated. Most of the delta-vees that you might pick out of the air won't go to the right place. So you might try a lot of different delta-vees and see which ones get the closest to where you do want to be, in the exact amount of time that you require the trip to take.

A method-of-Gauss, least squares kind of approach might work, where you take partial derivatives of the delta-vee components with respect to the spacetime location for arrival. (You can also do partial derivatives on the departure location, assuming that you can be flexible about the time, and hence the position, of departure.)

To get the partial derivatives, you first do your integration with an initial guess at the correct delta-vee, then find the state vector in the transfer orbit just after the departure burn. Then you find out where that delta-vee takes you in the amount of time you want to allow, and record the resulting position.

Next, you twiddle one of the delta-vee components just a tiny bit and repeat the integration process. The difference in resulting position divided by the difference in that delta-vee component gives you a numerical estimate for the three the corresponding partial derivatives.

In like manner, you repeat the foregoing until you have numerical estimates for all the partial derivatives.

d(Xarrival)/d(deltaVx)
d(Yarrival)/d(deltaVx)
d(Zarrival)/d(deltaVx)

d(Xarrival)/d(deltaVy)
d(Yarrival)/d(deltaVy)
d(Zarrival)/d(deltaVy)

d(Xarrival)/d(deltaVz)
d(Yarrival)/d(deltaVz)
d(Zarrival)/d(deltaVz)

These derivatives become constants in a set of equations relating changes in delta-vee with changes in arrival location.

delta Xarrival =
d(Xarrival)/d(deltaVx) [delta deltaVx] +
d(Xarrival)/d(deltaVy) [delta deltaVy] +
d(Xarrival)/d(deltaVz) [delta deltaVz]

delta Yarrival =
d(Yarrival)/d(deltaVx) [delta deltaVx] +
d(Yarrival)/d(deltaVy) [delta deltaVy] +
d(Yarrival)/d(deltaVz) [delta deltaVz]

delta Zarrival =
d(Zarrival)/d(deltaVx) [delta deltaVx] +
d(Zarrival)/d(deltaVy) [delta deltaVy] +
d(Zarrival)/d(deltaVz) [delta deltaVz]

So you relate adjustments in arrival position to small adjustments in departure delta-vee.

If your initial guess at the delta-vee was close, you can iterate toward the corrected delta-vee. Otherwise, you can get closer to the corrected delta-vee, recalculate the partial derivatives, and do it all again.

The advantage of your method is that the gravitational perturbations of all third bodies is automatically allowed for. The disadvantage is that it takes a lot more computer time to get the answer, in order to keep your time steps as small as they need to be.

Jerry Abbott
Last edited by Jenab6 on Mon 05 Jun 2006, 06:01:54, edited 3 times in total.
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Re: do you have a hobby? if so, what is it?

Unread postby Doly » Mon 05 Jun 2006, 05:22:30

As soon as you want to solve a three-body problem, the best way of going about calculating orbits is throwing away classic analysis and using numeric methods.

This comes from somebody who studied pure maths.
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Re: do you have a hobby? if so, what is it?

Unread postby SoothSayer » Mon 05 Jun 2006, 05:32:18

The disadvantage is that it takes a lot more computer time to get the answer, in order to keep your time steps as small as they need to be.

I can live with that, if it allows me to feel confident in what I have done.

You can also run an animation of the process to assist with visualisation.

Iterative approaches can also avoid problems with trig functions flipping at boundaries.

(I worked on a robot arm positioner once ... the software would occassionally totally flip when joints were at 45%)

I am of course rationalising ... I simply am not good with complex maths!
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Re: do you have a hobby? if so, what is it?

Unread postby Jenab6 » Mon 05 Jun 2006, 05:50:19

$this->bbcode_second_pass_quote('Doly', 'A')s soon as you want to solve a three-body problem, the best way of going about calculating orbits is throwing away classic analysis and using numeric methods.

This comes from somebody who studied pure maths.

Yeh? Well there's better ways of getting initial guesses about the departure delta-vee than just random guessing. That's what the analytical method is for. And besides that, if you're spaceship is travelling solo around the sun, and the transfer is intended to arrive at another isolated heliocentric parking orbit, the analytical method is close to exact. It's the gravity of third bodies that require it to be modified with complicated stuff.
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Re: do you have a hobby? if so, what is it?

Unread postby Doly » Mon 05 Jun 2006, 05:54:43

$this->bbcode_second_pass_quote('Jenab6', 'A')nd besides that, if you're spaceship is travelling solo around the sun, and the transfer is intended to arrive at another isolated heliocentric parking orbit, the analytical method is close to exact. It's the gravity of third bodies that require it to be modified with complicated stuff.


I'm talking about a real three-body problem, not what's in practice a two-body problem with perturbations.
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Re: do you have a hobby? if so, what is it?

Unread postby Jenab6 » Mon 05 Jun 2006, 06:10:45

$this->bbcode_second_pass_quote('Doly', '')$this->bbcode_second_pass_quote('Jenab6', 'A')nd besides that, if you're spaceship is travelling solo around the sun, and the transfer is intended to arrive at another isolated heliocentric parking orbit, the analytical method is close to exact. It's the gravity of third bodies that require it to be modified with complicated stuff.


I'm talking about a real three-body problem, not what's in practice a two-body problem with perturbations.

The difference between a three-body problem and a two-body problem with perturbations is how strong the perturbations are. The perturbations at departure and arrival can be strong enough to make the system effectively that of a restricted three body problem (the rocket's attraction of the sun and the planet can be neglected). Even though for most of the transfer orbit, the motion can be calculated as a restricted two-body system, the two-body math fails at either end of the transit, where the gravity of one or the other planet dominates that of the sun.

In the patched conic method, you calculate the pure heliocentric transfer orbit as a restricted two-body problem, then lop off the earliest and latest parts of the transfer orbit. These omitted sections are replaced with sections of escape (at departure) or capture (at arrival) hyperbolas whose state vectors meet the truncated ends of the (usually elliptical) heliocentric transfer orbit, with a sufficiently close match in velocity that the course correction won't be overly expensive.

Jerry Abbott
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Re: do you have a hobby? if so, what is it?

Unread postby MacG » Mon 05 Jun 2006, 07:22:46

Hobby? Well, since the divorce I took up an old hobby which had been dormant during the marriage: Women. Any guy out there who suspect that they are starting to lose som..er.. "abilities" because of age? Think again - it's amazing what some novel stimulus can do.
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Re: do you have a hobby? if so, what is it?

Unread postby frankthetank » Mon 05 Jun 2006, 12:03:40

Fishing, boating, gardening, biking (road mostly), socializing when i can, bird watching in my backyard. I would say that other then boating (i guess i could use a trolling motor!) all my hobbies require a minimal amt of oil.
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Re: do you have a hobby? if so, what is it?

Unread postby PrairieMule » Mon 05 Jun 2006, 12:23:17

Besides ranching and peak oil, I like to hammock camp. It's kind of a sub segment of the backpacking community they refer to us as "Wild Turkeys" or "Ewoks"(because we sleep in the trees). I have a Hennessy Explorer Deluxe Hammock and tricked it out with larger tree straps, 2 titanium tent pegs, under cover and larger silicone impregnated nylon tarp. The whose system weighs in a 3.5lbs stock/4lbs with extras and with further modification can give shelter in below freezing temps. The biggest plus side is that you can sleep in comfort in summer up to 85 degrees. The coldest I have endured was about 28 degrees.

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Re: do you have a hobby? if so, what is it?

Unread postby Wednesday » Wed 07 Jun 2006, 17:29:35

Jenab6 your link took me to a Neo-Nazi Hate Rock website which I found disturbing and offensive. White Pride? Gimme a break. It's just hate, plain and simple. There's no reason to be PROUD of your HATE.

Looking at that crap makes me sick. I didn't even get far enough into it to read your hobbies and now I dont feel like sharing mine.

Prussian blue is the color of the residue left behind by Zyklon B, which is the cyanide-based insecticide notorious for its use by Nazi Germany to kill over one million people in the gas chambers of Auschwitz and Majdanek.

It is also the name of a HATE ROCK duo who claim to be big fans of Hitler and admire his policies, they also claim that the Jewish Holocaust is a hoax. Aren't they just adorable in their Hitler t-shirts?
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This doesnt have much to do with PO but thanks for the reminder, I need to buy more ammo.
The individual has always had to struggle to keep from being overwhelmed by the tribe. If you try it, you will be lonely often, and sometimes frightened. But no price is too high to pay for the privilege of owning yourself.
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Re: do you have a hobby? if so, what is it?

Unread postby Kylon » Wed 07 Jun 2006, 18:38:19

That's wierd, I had to check that site out for a second, I was afraid it would have a large number of people. Thankfully I was wrong.

I think white racism, and black racism(which I dislike more, due to the fact it's aimed at me), is all around bad.
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Re: do you have a hobby? if so, what is it?

Unread postby pedalling_faster » Wed 28 Jun 2006, 11:49:20

* making stuff

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this is a silver bell, cast using centrifugal casting. i carved the wax myself and did the smokey, dusty part at a jewelry shop in El Cajon, California.

* and, drawing stuff ... learning animation software.

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a model of the Earth i created in 1996-1997.
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Re: do you have a hobby? if so, what is it?

Unread postby clover » Wed 28 Jun 2006, 12:40:46

$this->bbcode_second_pass_quote('Schweinshaxe', '')$this->bbcode_second_pass_quote('AmericanEmpire', 'D')oes beating off to porn count as a hobby?


You bet it does!

It's a nice little hobby... I try to combine it with my hobby as a power tool collector.


A very delicate combination...
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