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flytandem

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Forgive if this is the wrong place to post but I didn't see an interplanetary trajectory challenges forum.

In the interest of spicing up interest for interplanetary flights... I propose the following January 2009 challenge for anyone interested.

Start with any ship you choose sitting at Brighton Beach.
Ship launches any time on or after Jan 1st 2009.
Do a fly-by (within 10 radii) of any planet other than Earth.
Return to Earth before Dec 31st 2013.

Goal is to minimize the total dV of the trip.
Choose any fly-by planet you like.
No need to land safely on the Earth just show you are arriving to be able to intersect Earth on your return trip.
Make some saves during the flight to document the burns and dV used.
If interest is to extend the challenge beyond the end of January that's ok.
If there's no interest to even do this challenge, then that's fine too, I'll make the trip alone.:cheers:
 
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penlu

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Hard. Will you be rated or something better if you fly by a farther planet?
 

flytandem

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Hard. Will you be rated or something better if you fly by a farther planet?
Let's say that all planets are created equal. Score is just the deltaV.

OK let's be obvious... we are then talking about going to either Venus or Mars for the fly-by. Anything else will make the 5 year round trip both difficult and will add huge dV to the eject. The trick is choosing Venus or Mars. Go on Jan 1, or in the future, and when in the future. And it might need to be a sling of the planet to make the return to Earth a free ride which is the whole point... reduce the dV of the trip.

Plus the departure is from the moon which is a really fun can of worms.

This isn't really a tough challenge though. Just making the trip should be considered a winner. The stock DG has plenty of fuel to make the trip. Probably many ships can do it. I am curious how the dVs will range. I've not done this challenge yet. I glanced just roughly for a few minutes at Venus (without launching), but I've not looked at Mars yet.

rob
 

Andy44

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Interesting. According to Buzz Aldrin's Mars architecture article from Popular Mechanics a couple of years ago, you should be able to get to Mars and sling back to Earth repeatedly with very little dV expended. Unfortunately, his article did not contain any numbers. But if Buzz was right (and I'm sure he is, he's Buzz &*^%ing Aldrin!) then this challenge could be handled by an Apollo capsule atop a Saturn S-IVB upper stage, albeit starting from the lunar surface rather than LEO. No magic tech necessary.

Buzz has a PHD in orbit dynamics, IIRC. Would be cool to see him try his hand at Orbiter and publish his TransX setups online... One can dream, right?
 

Tommy

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I seem to recall reading that there are some good opportunities for free return trajectories to Mars in 2032.
 

flytandem

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I seem to recall reading that there are some good opportunities for free return trajectories to Mars in 2032.

Today TransX showed me that both Venus and Mars have free return slings within the 5 year limit for the challenge. I won't say which showed the lesser deltaV though. They're both pretty low. I went ahead and flew the one that appeared lesser. Fun trip. Thanks again Martin.

I got a new computer a few weeks ago and this is the first time I have fired up Orbiter with it. Seems to get a much faster frame rate. I've no clue what all the video options in the setup mean but whatever it has it looks great. Also, I had a series of a couple dozen CTDs during the flight that had me puzzled until I found out (I think) that a surrogate had decided to come along for the ride as a TransX stowaway in the scenario saves. Once I kicked it out the journey went onward without a hitch. :rofl:
 

Zachstar

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Also with a new computer comes more processes and crap.

Just to be sure I suggest uninstalling all the vendor crap they have on there and make sure your video drivers are nice and updated. (Unless it is intel onboard which means you are better off throwing the computer out a hotel window)

Edit: BTW flytandem one of these days you ought to do a few videos demonstrating your TransX "Skillz" Have you ever played around with video editing and capture? (Fraps)
 

Whatu

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The best I can do so far is get somewhere near venus...

I think I'm gonna devote some time to do every transx tutorials on your page flytandem... hopefully I will learn something and try again.
 

flytandem

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I wouldn't have a clue how to do FRAPS. I don't even have the ability to set up my computer to try the lunar lander challenge or any challenge using other than the deltaglider. Plus with FRAPS I don't think it would help convey the steps to solve something like this if you are looking for being really frugal with dV. Remember that just launching the moon and escaping the Earth at the outset and then looking for an opportunity to burn to head to Venus or Mars and then burn to capture, then burn to escape and then burn to head home is probably within the fuel limits of many ships. (deltaglide for sure) Most orbiteers would find this a challenge and feel great when they accomplish it. But to do it with minimal fuel use, would mean a gravity well burn... escape the moon, drop to Earth and when at periapsis just above the atmosphere do a single burn that is probably very small and after that coast to a sling and return of Venus or Mars... Here's some steps for this...



1. Start with a stock Deltaglider scenario like the one saying Brighton Beach. There's a ship at Brighton plus one on the Earth. Edit the date to Jan 1st of 2009 or since we are almost there remove the MJD number and replace with a semicolon, ex,
"Date MJD ;"

2. Launch the scenario and while sitting on the ground in the ship on Earth, fire up TransX and make a plan to escape and go to either Venus or Mars. Tweak the prograde and date to find a time where you can intersect and then fine tune close enough to be able to advance and sling back to Earth. Have an open mind to have the return trip multiple orbits but keep in mind the 5 year limit so not too many. If it doesn't work, try a different initial eject from Earth with more or less energy. This is the part that has the gut feel to reduce the time spent just fishing.

3. After you have a plan that works. Save it and write down the date of the eject. Also note what orientation the actual eject burn periapsis is at. The moon needs to be exactly opposite that orientation 4 or 5 days before the eject burn. This would only be lucky if it actually was there but the window to Earth depart for the planned sling might also be flexible. So advance the date toward the actual planned eject date and you'll need to see where the moon is as you approach the days and weeks prior to the eject date... (save your scenario with the plan)

4. Place yourself in the ship on the moon. TransX a plan to escape to the earth. You now see the location of the moon. Advance the date to see how the position of the moon compares to where it needs to be for the eject plan you made for the ship on the Earth. If you need to, go back to the other ship and tweak the plan to modify the eject date as needed to earlier or later as needed to get the moon to be opposite the eject periapsis 4.5 days before the eject date. Remember to always allow for the time to transit from moon to Earth. It's possible the eject date is critical and the moon isn't in the right place. I've found it's usually a workable change to the plan to match having the moon positions properly.

5. Advance the date to 6 days before the planned eject and either with the scenario editor or just flying, (I like to fly it) launch the Earth ship when the ship (from Earth's rotation) is crossing the plane of the moon's orbit. Use Map MFD, target moon. Launch heading should be to be to have you in orbit aligned with the moon's orbit. Now on your first orbit as you are approach being directly under the moon, have TransX up with the first stage showing the Eject Orientation and swing the white line around to your position. It will now tell you how much you are off. Burn normal to change your orbit. Note: you are getting an orbit wher you are both with the moon in position of the plane of your orbit, PLUS you are oriented to be able to fly the plan you have to go to Venus or Mars. Burning when crossing the moons orbit to align with your plan. Then when half way between where your orbit crosses the moon burn normal to make you orbit cross the moon's position.

6. Now you have a ship on the Earth that is capable of doing a prograde eject burn to head to Venus or Mars. And the ship on the moon is in plane in its position with that ship on the Earth. So set up a plan on the ship on the moon the escape to Earth and target the ship in orbit around the Earth. You want to arrive aligned with the Earth ship but you don't need to intersect or rendezvous with it. You will also want to arrive just above the atmosphere. (150 km agl?) Change the stage 2 graph projection to "plan". Modify the eject variables so that it makes the Earth ship orbit as full a perfect circle as possible. This makes you very much arriving at Earth aligned with the ship already in orbit around the Earth, PLUS your periapsis orientation will be very close to the periapsis of the eject plan to head to Mars or Venus. Launch the moon and head to Earth according to the 2 stage plan. As you get to a couple hours or less from the periapsis at Earth simply set up a maneuver to eject to the other planet and you should also be able to hopefully have it close enough to allow planning the sling and return to Earth from what you remember of the plan the other ship had created.

You should make plenty of saves. Also I think TransX might end up with the named ship in the coding of the scenario as having two separate line entries with all this changing of ships and planning and saving. You might need to manually delete the incorrect ship name once you no longer need the surrogate that was in orbit at the Earth.

Here's an example of a ship orbiting Earth with the moon positioned in plane with the orbit and with the ability to go to another planet with a single burn in the next few days. And there is a ship that has just left the moon and will coast to the Earth (it's going to become 2.5 degrees out of alignment with the Earth ship but that's close enough ;)

BEGIN_DESC
END_DESC

BEGIN_ENVIRONMENT
System Sol
Date MJD 55147.7524652998
END_ENVIRONMENT

BEGIN_FOCUS
Ship 4
END_FOCUS

BEGIN_CAMERA
TARGET 4
MODE Cockpit
FOV 60.00
END_CAMERA

BEGIN_HUD
TYPE Surface
END_HUD

BEGIN_MFD Left
END_MFD

BEGIN_MFD Right
END_MFD


BEGIN_SHIPS
3:DeltaGlider
STATUS Orbiting Earth
RPOS 1987661.36 3713656.64 5139245.89
RVEL -7350.764 983.307 2199.517
AROT -55.24 -3.48 171.36
RCSMODE 2
PRPLEVEL 0:0.628 1:0.992
NAVFREQ 0 524 84 114
XPDR 6
PSNGR 2 3 4
TRIM 1.000
END
4:DeltaGlider
STATUS Orbiting Moon
RPOS 688118.35 902496.61 -1356383.37
RVEL 1576.249 1212.124 1534.542
AROT 39.43 -39.34 -61.88
RCSMODE 2
PRPLEVEL 0:0.881 1:0.995
NAVFREQ 402 94 0 0
XPDR 8
RCOVER 1 1.0000
END
END_SHIPS

BEGIN_ExtMFD
END
 

HiPotOk1978

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maybe someone should try to find an e-mail for Buzz and send him the link to the forums and the sim?
 

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maybe someone should try to find an e-mail for Buzz and send him the link to the forums and the sim?

Just don't question his trip to the moon. :)
 
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