Windows of Opportunity!?

[freespace2dotcom]

Hey, I'm serious here. would anybody help a poor guy out and give me some launch windows for traveling to the
other planets from earth? I have a few for going to mars, and I *had* one for jupiter, but I never saved the date
(d'oh!)  I hunted a few leads on google, but they were mostly dead ends. The only one that had promise told me how
to hunt them down manually in orbiter by changing the dates. But that's a lot of work for me.. (me = lazy)

if anybody would volunteer some of their time and give me some dates to work with. I'd be very thankful to you.

(no indentured servitude, though)

[freespace2dotcom]

Grrrrr. You people are worse than even ME! I'm way too impatient to wait a day before a response. But I guess none of you guys had the dates on hand.

I got around to it. I wanted launch windows, now I shouldn't have to screw around with this stuff anymore.

These dates are pretty far in the future, but they are valid as far as I can tell. I'm sure the solar system will be explored
at a far faster rate now that these are out. just pop them into your scenarios and you're good to go.

Mercury 60911.52
Venus 60672.5
Mars 60583.52
Jupiter 60939.29
Saturn 61199.4
Uranus 61247.4
Neptune 61552.6

*NOTE*  these dates only take into account the earth's and the planet-in-question's positions around the sun. You
might have to fine-tune it to get a better launch window depending on where you are on the earth. You might also
want more time to get into position. But frankly I don't think you'll need to change it any more than a day or so.

Happy orbiting!



Post Edited ( 05-14-04 03:18 )

[Arkalius]

April of 2003 was the window used by NASA to launch the two latest Mars probes. Mars windows show up every 20
or so months, so the next one after that would be December of this year.

[freespace2dotcom]

eh.. OK... I just hunted down the dates. These dates are in 2020 or so? didn't look carefully.. anyway. I have the
dates now, which is good enough to get there so long as nobody minds it being that far ahead in the future. And I don't see why they would.



Post Edited ( 05-14-04 06:09 )

[AphelionHellion]

Yayyy!
Thanks freespace
I keep forgetting that a transfer to Mars is a bit different from a transfer to a satelite or moon. Normally I just open the
transfer MFD and then turn on time acceleration until I'm where I need to be. Using that method to get to Mars or a
planet, though, and you'll either run out of oxygen or patience, real quick

[DocHoliday]

Aphelion, I was just going to suggest to Freespace to use TransX to get the launch window and then manually
change MJD in the .scn to a few hours before that.

BUT, there is a very efficient method to calculate this sort of things. I found it at:
http://www.marsacademy.com/laopp.htm and then I created a VERY simple Excel table that should yield a launch
window for any date you want. I will add this to the "conversion" table I once promised before and post it as soon as
I find them

Basically, what you are dealing with (again) is the relative angle between the two planets. Periodically the two
planets come to a correct relative position for you to do a hohmann transfer. For Mars and Earth, the correct angle is:
Mars has to be 0.773 radians AHEAD of Earth, when you start your interplanetary burn. This will ensure, that when
you get to the the apoapsis of you transfer orbit, Mars will also be there. For other planets this angle is different, but
calculated the same way. All you really need is one single data at which you know the exact position of the two
planets with regard to eachother and you can then calculate future or past occurences of the correct relative angle,
because these planets are quite predictable in their migration habits

Anyway, that's in a nutshell. I know you're lazy so I probably lost you by mid second paragraph

[AphelionHellion]

Hey, I am NOT too lazy to read!

Coming up with an excel table on the other hand...

Hey, we should start compiling this stuff. Julian dates for several windows in the future from each planet to each
planet, your table(s), a basic explanation of principle... Sort of an Orbiter Almanac

[freespace2dotcom]

DocHoliday wrote:
I was just going to suggest to Freespace to use TransX

Who do you think I am? GOD?

I can't figure out any of that *EVIL* (emphasis on evil) proggy. and for those of us who are weak minded and would
rather just see a list and take a number, (which is far easier than using said "evil") I think I did quite well. Now then, I
admit that looking back, my venus date seems a bit off now, but it shouldn't matter for all of you "evil-using smart
people". all in all, if you're just looking for a date to get you to where you want to go, then my little list willl get you
there. for those who want a more realistic date closer to present, and are too good for the list, then you can go to all
the effort of making that huge almanac thingy when other resources could go to such things as that story we were
sorta working on..

in any case, let anybody who wants to use it, do so, and if you don't want to, no biggie. (just don't be crying to
me 'cuz I'm too lazy to appeal to the random person.)

TransX is evil through it's complexity. it isn't noticable by those who can use it.



Post Edited ( 06-07-04 22:07 )

[AphelionHellion]

Freespace: I don't think TransX is evil, I think it's just broken. That's the only possible explanation... At some point we
all downloaded a corrupted version, maybe it was the last update? Because no matter what I do it doesn't friggin'
work! Arg!!

I've been having fun with the basic transfer MFD, but it isn't really accurate enough for those interplanetary transfers.
Youy can get there but you don't end up that close to the planet you're trying to get to. You need to manually get in
close at the end... At least it works though

[freespace2dotcom]

Eh? there is NOTHING wrong with the basic transfer MFD. I too have problems getting anywhere near the planet I
burn towards, but that is because I simply don't have any way of knowing WHEN to perform said burn. I can easily
correct once I'm on my way, (getting close enough) but that's not efficient fuel wise. and I remember having a hell of a time getting there with the default DG. the very first time I tried I got there but had used all my fuel for course
corrections early on so I couldn't get captured into orbit. but seriously if I have fuel, I can get to within, say, about 50
percent of mars' sphere of influence, which isn't very close I grant you, but quite frankly, I just don't practice the
manuver at all. there's lots of room for improvement. if I could find the right time to perform my escape burns, then I'm
sure I could get to within a couple hundred kilometers if I really applied myself with practice. Ironic it is, though, that
the way I get to mars is still thanks to that duncan guy who made transX, he set up that tutorial for going to mars
with the default mfd's and I've used those principles ever since.

Freespace, who's singing "it's a small world after all" over and over. at least the first verse, anyway. he knows that.



Post Edited ( 06-07-04 23:23 )

[reekchaa]

Freespace, you 'weak minded' Living Legend!    ...You're a Five-Star Wanker!  

hehhe... I'm on a roll.  (sorry, I couldn't resist)  

[Atom]

How exactly would you know that Freespace is a wanker?

[AphelionHellion]

freespace2: Agh!! What am I doing wrong?
I keep plugging your numbers into Julian/Gregorian date converters and I keep coming up with the year 4548 BC or
something. When I plug in a current date to convert it to Julian dates, it gives me a completely different set of digits
than yours.
 

[Schimz]

Some Lw, Mars USSR program :
http://en.wikipedia.org/wiki/Mars_probe_program

[DocHoliday]

AphelionHellion wrote:
Hey, I am NOT too lazy to read!

Easy. That was directed at Freespace not you

Coming up with an excel table on the other hand...

Hey, we should start compiling this stuff. Julian dates for several windows in the future from each planet to each
planet, your table(s), a basic explanation of principle... Sort of an Orbiter Almanac

Well, true, but a lot of work has been done by people far better than I am capable of. I was just studying the things
Conley, Croy and some others came up. Pretty darn amazing. Basically everything is already done and to compile it
would just require their permission. And a lot of work and insight... :/ maybe someday, when I break a leg and have
too much time on my hands

Interesting about the TransferMFD and TransX. I usually had problems with the former. Especially the bit, when you
actually start the burn. I was never able to align my ejection hyperbola to the one I had planned for! With TransX you
get the maneuver view, which helps you time the burn and orient the ship properly. All in all TransX is a lot better, but
takes time to grasp it and configure it... did you go through the manual and tutorial??? (PLEASE say you haven't,
becase then there is hope for you!)

And stop hiding your sharp mind behind lazyness, claiming weak-mindedness. It's getting old and we all know better,
you did some nice work with the temp bug, reviewer crack and the skin... so.. there :P

Cheers,

[Simonpro]

AphelionHellion wrote:
freespace2: Agh!! What am I doing wrong?
I keep plugging your numbers into Julian/Gregorian date converters and I keep coming up with the year 4548 BC or
something. When I plug in a current date to convert it to Julian dates, it gives me a completely different set of digits
than yours.
 

Erm, *Julian* date converter?? Orbiter uses the modified Julian date!

[DocHoliday]

Try this: Modified Julian Date = Julian Date - 2,400,000.5

Hm?

rulz!

Cheers,

[freespace2dotcom]

AphelionHellion wrote:
I keep plugging your numbers into Julian/Gregorian date converters and I keep coming up with the year 4548 BC
or something. When I plug in a current date to convert it to Julian dates, it gives me a completely different set of
digits than yours.
 

I get that same problem too. I don't know what the difference between orbiter's date system is between the
julian/whatever system is if there even is one, but you plug those numbers into orbiter, and it will work fine.

DocHoliday wrote:
And stop hiding your sharp mind behind lazyness, claiming weak-mindedness. It's getting old and we all know better,
you did some nice work with the temp bug, reviewer crack and the skin... so.. there :P

actually, I did sorta read the transx manual, but after a while it got monotonous, so I gave up. (it's evil...)

And yes I am lazy. you haven't seen my room, have you? you remember my computer I told you about? well I bought
it way back in december, but I finally got the boxes it came in out of my room just yesterday. they were big boxes.
one was maybe 3ft by 3ft, and then I put the others in the big one. and it was taking maybe a good 1/10th of my
room space, and I would have left it there too if not for my uncle's wanting to move my dresser out of the living room...

computers attract wires, and wires attract tangles. that, we all know. but my wires attract knots. and these knots
don't unknot without work, and to unknot them, it would require turning off the power to my computer, which only
goes out during blackouts. the floor has not been swept or mopped since I moved in, and I never change my
bed/couch hybrid into a bed to sleep in at night. I leave it as a couch, cuz it's easier. Oh, and did I mention I'm a
potato chip thief? my house is deprived of them because of me.

I'm weak minded in that I'm too lazy to do mental work when it's boring. I have a hard time to concentrate during
boredom, and is that not a sign of a weak mind?

oh, two for two, man I'm burning. well, no I'm not. I finally got air conditioning in my house. My poor 'puter was dying
at 143 degrees F (that's 61.3 C) far hotter than I would ever want it to get.

also, about venus's transit. I found this cool chart. almost all of europe can see the whole thing. (I hate you guys for
that!) you guys gotta tell me about it. even though It'll be seeable in the morning for me, and I'll be able to see the
end of it, I suspect that it'll be cluttered by things like trees just over the horizon so I'll likely miss it. doc, you have to
show me a pic.  

[DocHoliday]

Schimz wrote:
Some Lw, Mars USSR program :
http://en.wikipedia.org/wiki/Mars_probe_program

Wikipedia.. Interesting. Orbiter is also noted in there already. We should add Deltaglider

But let me get this straight. ANYONE can edit ANY post that is on there??? Isn't that kind of ... asking for trouble,
especially on sensitive subjects where opinions might differ? Or even facts might not be agreed on??

[AphelionHellion]

Ohhhhh, MODIFIED Julian date.
I feel dumb  That certainly explains the problems I was having, though.

Grrr... I'm disappointed with
I've been looking for transfer window information for Mars (or any planet for that matter).
Most of the stuff I've found is mentioned in passing, along the lines of "there will be another window around 2007"
Gee, thanks!

[DocHoliday]

Heh, I call lazyness.. "a specialized set of priorities" I am by most standards lazy too. You should see my WHOLE
appartment. Haven't vacuumed the place in ages.. Anyway, but when I do get something interesting (for me that is)
to do, I can spend hours with total concentration on it.. OR it can be presented to me in such a way I interpret it as
interesting. Same with you I guess.

cleaning, cables, comfort = low prioriry
mental challenge, things to facilitate it=high priority

Most people believe otherwise. As they wish. With TransX you should set one single simple specific goal to start with
and when you get it done, it will seem a lot easier to use. Like going to the Moon. For that you don't even need an
MFD, if you're a real hotshot. So it should be a breet to get there with TransX. First align your orbital with the moon to
skip that part of TransX. Set your target to Moon. Turn on the Maneuver mode.  Set a prograde burn that gets the
ellipse to the moon and then turn the ellipse by changing the launch date forward (on a setting like Super or Ultra)
until the yellow lines overlap. Minimize the perigee distance (launch date and prograde adjustments will do that) and
when you get it to some nice low number, press FWD to set up stage 2. You will then see what your hyperbolic orbit
around the moon will look like. If it looks suitable, go back to Stage 1, change to Target mode and orient your ship to
the cross in the display, wait for the time and burn.. that's it.. you can do the moon orbit caputre burn manually, no
sweat. Or you can fiddle around to get that down to a science too.

I mean things like TransX are basically IDEAL for lazy people like us. The only unlazyness involved is understanding
how to use them. Tell me how it goes.

doc, you have to show me a pic.

Actually I this Venus thing kind of doesn't interest *me* for some reason, but I'm sure the net is gonna be full of
photos.. just google

But just for you:

http://www.24ur.com/media/images//extra/Jun2004/6006551.jpg

Don't know what this pic's orientation is but this looks like a non-equatorial or a high inclination passing anyway..
Cheers,

[AphelionHellion]

Atom: Simple - he's under 60, so he's a wanker. Duh!  
Hey, what are we supposed to do on that 8 month trip to Mars?  

*American Wankalogical Society Charter Member*

[AphelionHellion]

DocHoliday: Yeah I have that problem too, I find it helps to start the burn a tiny bit early and make sure to turn on that
turbo pump) I normally use the high-thrust motor on the DGIII when going interplanetary  

[AphelionHellion]

DocHoliday: Heh, oh there are some disagreements alright. I notice that certain subjects are locked to most or all
users. If I recall correctly, some politically and religiously oriented subjects have little disclaimers that basically say
"This subject is in dispute by a number of people and you should probably draw your conclusions from more than one
source." I understand that the folks who run it have sort of a committee that decides which entries to approve, also.
They must do a pretty decent job because I don't see any "j00 $uX()rZ I /\m 1337!!!111111!!!" entries in there as of
yet. I get the impression that it's more like a normal encyclopedia that you can update (IF you have something useful
to add) than one of these knowledgebases that are more or less organized anarchy

[DocHoliday]

Actually as far as I can remember, the basic formula for the burn goes like this:
if you know the time it will take to reach the required deltaV (BurnDuration), and you know when the this change of
speed should occur (BurnInstant), you calculate the proper start of the burn like so:
Start of the burn = BurnInstant - (BurnDuration/2) -> Example:
BurnInstant = 300 sim time - this is when the change should occur (usually perigee or some other extreme) if it were
instant.. if you had like warp engines
BurnDuration = 80 seconds - this is the time it will take you (with the current ship) to reach the required delta V

So you start your burn = 300 - (80/2) = 260 sec sim time -> so 40 seconds before you reach the point.

How to calculate the burn time? Well, it depends on the engines, specifically, ISP, or in our case, how much
acceleration they produce. This figure changes with time, but for small deltaV it is not significant, but it's easily
acquired. In Deltaglider the engine status display tells you directly (the figure with m/s^2).
The formula is simple -> a=v/t (velocity change/time change) or rather t=v/a
so if your vessel accelerates at like 6 m/s^2, you should achieve a deltaV of 480m/s in 80 seconds.

Simple?