Chapman Challenge

[Whatu]

I have to say that is an awesome flightplan, flytandem!
Im gonna have to try flying it... maybe when I get a bit better..

 

[flytandem]

I want to offer a bit of quick advice on the flightplan. You could simply enter the initial departure data as provided and fine tune to make the arrival at Venus on the correct day (plus or minus a day would probably work) When you are half way there set up the next sling (in this case Mercury). You could keep slinging each leg of the trip when half way to the next sling set up the following sling. Be sure to keep an eye on the arrival dates when setting up the slings because sometimes you go directly there and sometimes it could be some orbits pass before the next encounter. Most are withing 1 orbit but in one case, when going from Mercury to Venus, it's a 3 orbit wait before the encounter. To set up the sling for future orbits, in setup view, adjust the variable "orbits in icept", and so for the Mercury to Venus leg you must set this value to 3.

BTW the sling at Earth is always a pain because of the binary boogy it does. There is a reason that Earth is only slung once. :lol: What I do is to do a final MCC when 1 lunar orbit (2.36 megaseconds) from passing Earth. Do a save there, and run it to see how far off it is, then go back and compensate for how much it missed and in what direction to give it a second run. If it's reasonable you are then on your way to Jupiter.

I must have done 50 or more overall variations that all failed before finding this solution. But there are probably many other solutions that work and no doubt some are better than this one with fewer slings and perhaps a later launch date.



Oh and I don't yet know much about how the Chapman probe works, (hope to soon) but if it can be pushed with a departure dV of about 6300 m/s from LEO , and if it then has the ability to do minor corrections that amount to a total of 600 m/s dV over a 20 year period, it is conceivable that the probe could do the fly-by tour of ALL the planets.
rob

 

[mbartley]

BTW the sling at Earth is always a pain because of the binary boogy it does. There is a reason that Earth is only slung once. :lol:

I thought that was improved in TransX version 3.11.
http://orbiter.quorg.org/
heading "Change Log"

 

[tblaxland]

Oh and I don't yet know much about how the Chapman probe works, (hope to soon) but if it can be pushed with a departure dV of about 6300 m/s from LEO , and if it then has the ability to do minor corrections that amount to a total of 600 m/s dV over a 20 year period, it is conceivable that the probe could do the fly-by tour of ALL the planets.
rob

Nice work, flytandem. A Delta IV Heavy could certainly achieve 6300m/s, and I'm pretty sure a number of the Atlas V variants could also. The Chapman Probe itself has about 2,000m/s on board so the 600m/s requirement for MCCs is no problem either.

 

[astrosammy]

Looks like I'm getting the slingshot thing right now. I just flew to Saturn after a Jupiter slingshot (launch was in late 2016). Some months before encounter I decided to aim for a very low Titan flyby. So I came perfectly in for a 150 km periapsis (in the upper atmosphere) and turned my Delta Glider around to keep it in this altitude. I changed Orbit MFD reference to Saturn waited until my orbit around Saturn got nearly circular. At that moment I pulled up to get out of the atmosphere and were in a nice orbit, without any use of my engines. Now I'll try to get some Venus slingshots before the Jupiter slingshot and get my fuel use to a minimum. When I've done that I think I'll be ready for future Chapman Challenges. (BTW, thanks for your tutorials, flytandem, without them I wouldn't be able to do this)

 

[atuhalpa]

Bugfree orbiter install

Flytandem, I have just now finished putting together an orbiter package that is bug free (at least on my machine), has all the planets and moons, the chapman probes, the asteroid pack, and the trojan pack that Piper put together. I am going to burn it to disc and then test it one more time. If it is a go I will put it in the mail tomorrow (2/2/09). Whether or not you launch the Delta heavy or the stock delta glider it will give you a multitude of rocks to visit.

 

[flytandem]

I thought that was improved in TransX version 3.11.
http://orbiter.quorg.org/
heading "Change Log"

I'm definitely not the expert in the details of what was done but it did get an improvement over previous. It is definitely better. I think it used to take the motion of the Earth at any one time and predict the encounter based on that (as if the moon suddenly disappeared) maybe not. But I think it now uses the barycenter of Earth and moon combination which runs a predictable orbit so when you are several months away you can get a much closer approximation of how you will hit relative to this barycenter. But when you are coming in for the last few days the sling position is supposed to be a very precise distance from the Earth itself not the barycenter. In any event, compared to slings at Mercury Venus and Mars, they are very stable and Earth still has an extra challenge. This is why I have tried with a modest amount of success at fine tuning the sling at exactly one moon orbit ahead. It places the Earth about the right position in its orbit around the barycenter and since it's so far ahead in time, any correction then would be small. In the worst case you will simply need to do a few extra corrections in the last few days and hours before the sling.


-----Post Added-----

Flytandem, I have just now finished putting together an orbiter package that is bug free (at least on my machine), has all the planets and moons, the chapman probes, the asteroid pack, and the trojan pack that Piper put together. I am going to burn it to disc and then test it one more time. If it is a go I will put it in the mail tomorrow (2/2/09). Whether or not you launch the Delta heavy or the stock delta glider it will give you a multitude of rocks to visit.

Thanks!

 

[Piper]

Flytandem, for the MPC Database Viewer/Exporter, try installing these:

Visual Basic Run-time files

 

[flytandem]

Flytandem, for the MPC Database Viewer/Exporter, try installing these:

Visual Basic Run-time files

Hmmm. I got a new computer a couple months ago that runs vista. I noticed some old apps I had made weren't working. One of them was a pool sim I made using visual basic. No worries though. Never really did anything with it,... it was just a project to see if I could remember my highschool math from 30 years earlier. I forgot that it needed some files specific to visual basic which I am now just realizing that it needed. I just ran the vbrun exe and, lo and behold the pool app runs. Now I'll download the MPC database viewer and see if it does any better. Thanks Piper. Hey, what part of Canada are you from? (never mind just saw your info is Ottawa) I grew up near Hamilton before moving to California at age 24. I worked for a short while at Telesat in Ottawa. I quit because I would rather have a cool job in a hot climate than a hot job in a cool climate. :speakcool:


-----Post Added-----


The Minor Planet program seems to run. Yay. It shows something like 35000 chunks of rock. Haven't figured out how to run the app correctly yet. Crashes with runtime error and path not found when I try to send a rock to Orbiter. I'll try again tomorrow.

 

[tblaxland]

Crashes with runtime error and path not found when I try to send a rock to Orbiter. I'll try again tomorrow.

There is an option under the File menu to set the correct path for your Orbiter installation, IIRC.

 

[atuhalpa]

Flytandem, I had the same problem with path not found and I went into msconfig and turned some stuff back on that I had turned off. Have you disabled some of your resident programs in startup?

 

[Piper]

I just wanted to give a quick update on the next Chapman challenge. I'm still working on the next version of the Chapman probes, which will have corrected weights (looking at other spacecraft, they were still on the light side), and two new versions propelled by Hall effect thrusters, with a whopping dV of over 20,000m/s (and that's with less fuel then the other ones).

I'm also going to include a page on my website with more detailed information about each of the probes, including their calculated distance and performance limitations. I will also have a page that will contain launch scenarios that you can download for different launchers for each of the probes, and the requirements to run each launcher. This should all be done by the 15th, as I'm more then 90% done now. By the way, I will be using one of the Chapman Ion probes for the advanced challenge, however I haven't decided on the target yet (although I'm leaning towards Ida).

If you want practice with low-thrust spacecraft trajectories, I recommend trying either BrianJ's [ame="http://www.orbithangar.com/searchid.php?ID=3459"]Dawn v2[/ame], or download his IEATMFD (by the way BrianJ, you really should should upload that to Orbit Hangar, it is simply amazing!) and lower the thrust on a Chapman probe to 0.154N, and increase the ISP to about 29,000m/s.


- Chapman Ion-2 orbiting Ida's moon Dactyl, at an altitude of about 100 meters.

:edit: mods, since we're well past the first Chapman Challenge, could one of you rename the thread to just "Chapman Challenge"? Thanks.

 

[atuhalpa]

Flytandem, the orbiter disc is in the mail this pm(2/3/)

 

[mbartley]

I think it used to take the motion of the Earth at any one time and predict the encounter based on that (as if the moon suddenly disappeared) maybe not. But I think it now uses the barycenter of Earth and moon combination which runs a predictable orbit so when you are several months away you can get a much closer approximation of how you will hit relative to this barycenter. But when you are coming in for the last few days the sling position is supposed to be a very precise distance from the Earth itself not the barycenter.

OK, I guess I have noticed TransX doing this before, but didn't know what was going on.

As a test, I just flew a DeltaGlider from Jupiter to Earth. I used IMFD for launch out of Jupiter orbit, then a combination of TransX and IMFD's Map function for course corrections. 3 months or so away from Earth, I had the approach refined so that IMFD showed me reaching Earth with the minimum possible inclination and with a perigee of 250 km.

However TransX showed my perigee at around 4100 km. Once I got within around a day from Earth, TransX suddenly changed to showing my perigee as close to 250 km. I didn't pay attention to the position of the moon during all this, but does that sound like a barycenter effect?

In any event, compared to slings at Mercury Venus and Mars, they are very stable and Earth still has an extra challenge. This is why I have tried with a modest amount of success at fine tuning the sling at exactly one moon orbit ahead. It places the Earth about the right position in its orbit around the barycenter and since it's so far ahead in time, any correction then would be small.

I'll try that.

 

[flytandem]

Flytandem, the orbiter disc is in the mail this pm(2/3/)

Thanks. Just got the disc and did a flight test to see things like control and deltaV. Did a generic random easterly launch and had to dip 5% into the booster fuel for a circular 160 km orbit. It still left something like 6850 or more m/s deltaV in the Booster.

I noticed the acceleration of the booster is fairly slow but should be within reasonable ability to keep on a TransX heading. Just a bit tougher than with a fast acceleration. I suspect the burn might be several minutes duration so it will have to start fairly early and there will be some directional adjustments to get the burn exact. But with 6850 m/s it opens up huge possibilities. Even the enhanced grand tour should be cake.

After that I guessed correctly and "J" caused separation and the probe was loose. Switched ships to become the probe and saw it also has a large amount of deltaV. Its acceleration is slow but for MCCs it is plenty.

When I get a chance I'll either take the probe for a run at the enhanced grand tour or perhaps I'll start looking at all those rocks in the package.

OhBoy... more fun.

thanks again atuhalpa


-----Post Added-----


Here's a flight report to Meges.
I started the planning by placing a surrogate on Jupiter so I do some homework and look at sling velocity values and toggle through the various asteroids in the pack I received. I opted for Meges. By using a surrogate I could see where the node with the asteroids were and then quickly change the sling date to be on the node and then the sling velocity value and sling angles to look for something that allowed a slow encounter at Meges. I figured why waste the time setting up the transfer from Earth if the choice of asteroid was poor.

Then I set up the TransX plan for the rocket on Earth and planned a transfer that arrived at the correct date with the correct encounter velocity. In fact it turned out that I couldn't get the correct arrival speed and date very well but what could be obtained I ran through the sling to see the effect at Meges encounter. The surrogate had shown something like 1500 m/s Meges encounter but the change of plan increased it to 2200 m/s. Should easily be do-able I though given the 3800 or more m/s carried on the probe.

Launch went as planned but I dipped 10% into the upper stage fuel. It still had a bit extra left over after the Jupiter transfer.

The Jupiter sling was typical and floated the value a bit on the arrival and departure.

The full orbit between Jupiter and Meges had me chasing the asteroid a bit. Both TransX and IMFD were showing the closest approach as doing a constant drift almost like the Chapman Probe was behaving under a slightly different pull of gravity than Meges was feeling. So it required probably 10 corrections in the final weeks to the encounter.

TransX worked well to arrive 5km above the surface with a predictable braking burn of the expected 2200 m/s. A nice circular orbit 5km agl was achieved with 1122 m/s spare deltaV.

So I decided to burn up a bit more and land. Funny thing is I wanted to land softly on its side to have the camera point (forward view) at the horizon but at the moment it switched to "landed" status it defaulted to an upright attitude. I had no idea it would cop such an attitude for being forced to land.

Here's the scenario of the Meges orbit before doing the landing.

BEGIN_DESC
Orbiting Meges.
END_DESC

BEGIN_ENVIRONMENT
  System Sol
  Date MJD 60624.2690140636
END_ENVIRONMENT

BEGIN_FOCUS
  Ship Fregat1
END_FOCUS

BEGIN_CAMERA
  TARGET Fregat1
  MODE Cockpit
  FOV 50.00
END_CAMERA

BEGIN_HUD
  TYPE Docking
  NAV 0
END_HUD

BEGIN_MFD Left
  TYPE User
  MODE TransX
  Ship  Fregat1
  FNumber 1
  Int 5
  Orbit True
  Vector  31134.704834 3379.92080688 -8492.50830078
  Vector  0.226379654547 -12.7891199437 -4.75156146508
  Double  6007686.44438
  Double  60624.2690141
  Handle Meges
  Handle NULL
  Handle NULL
Select Target
 0 None
Autoplan
0 0
Plan type
0 1
Plan
0 0
Plan
0 2
Plan
0 0
Select Minor
 0 None
Manoeuvre mode
0 0
Base Orbit
0 0
Prograde vel.
 0  0
Man. date
 0  60624.2690141
Outward vel.
 0  0
Ch. plane vel.
 0  0
Intercept with
0 0
Orbits to Icept
0 0
Graph projection
0 1
Scale to view
0 1
Advanced
0 0
Draw Base
0 0
Finvars
  Finish BaseFunction
END_MFD

BEGIN_MFD Right
  TYPE User
  MODE TransX
END_MFD


BEGIN_SHIPS
Delta4HV:Delta4HVD4HV
  STATUS Orbiting Sun
  RPOS -2173392523635.76 49821578146.64 -848510741472.37
  RVEL 238.271 16.576 -5176.133
  AROT 119.71 -80.99 -48.46
  PRPLEVEL 2:0.014
  NAVFREQ 0 0
  CONFIGURATION 2
  PAF 3
  MET 420936997.7
  HEIGHT 25.0
  UPGRADE 
END
Delta4HV-SRB2L:Delta4HVD4HVsrb2
  STATUS Landed Earth
  POS -51.9110621 5.0491134
  HEADING 41.71
  NAVFREQ 0 0
END
Delta4HV-SRB2R:Delta4HVD4HVsrb2
  STATUS Landed Earth
  POS -51.9465091 5.0373290
  HEADING 259.13
  NAVFREQ 0 0
END
Delta4HV-SRB1L:Delta4HVD4HVsrb1
  STATUS Landed Earth
  POS -51.9013917 5.0503050
  HEADING 246.01
  NAVFREQ 0 0
END
Delta4HV-SRB1R:Delta4HVD4HVsrb1
  STATUS Landed Earth
  POS -51.9319331 5.0378579
  HEADING 251.62
  NAVFREQ 0 0
END
Delta4HV-LHB:Delta4HVD4HVboo
  STATUS Landed Earth
  POS -46.0078584 5.9111468
  HEADING 104.06
  NAVFREQ 0 0
END
Delta4HV-RHB:Delta4HVD4HVboo
  STATUS Landed Earth
  POS -45.9973448 5.6050857
  HEADING 17.17
  NAVFREQ 0 0
END
Delta4HV-STG1:Delta4HVD4HVcore
  STATUS Orbiting Sun
  RPOS 43250268701672.23 9294356921115.13 -11228326068061.65
  RVEL 102504.800 22055.460 -26278.448
  AROT 39.93 -47.60 -142.74
  VROT -9.29 -6.16 -18.99
  NAVFREQ 0 0
END
Delta4HV-LHF:Delta4HVD4HVfair3
  STATUS Orbiting Sun
  RPOS -8853124891.80 3431640788.02 250135587994.01
  RVEL -19695.538 -1033.034 -3479.318
  AROT 154.30 -45.49 -80.87
  VROT -21.51 0.00 0.00
  NAVFREQ 0 0
END
Delta4HV-RHF:Delta4HVD4HVfair3
  STATUS Orbiting Sun
  RPOS 338296505047665.81 78195183608129.38 -128153798982952.11
  RVEL 803554.377 185765.168 -304098.943
  AROT 53.01 19.36 -160.39
  VROT 0.07 1.29 0.15
  NAVFREQ 0 0
END
Fregat1:cvelfregat
  STATUS Orbiting Meges
  RPOS 31134.70 3379.92 -8492.51
  RVEL 0.226 -12.789 -4.752
  AROT 69.63 1.51 73.86
  PRPLEVEL 0:0.190
  NAVFREQ 0 0
  XPDR 0
  PAYLOAD ChapmanOuter ChapmanOuter SpacecraftChapmanOuter 0.00 -0.15 2.00 1365.00 0.00 1.00
END
END_SHIPS

BEGIN_ExtMFD
END

 

[atuhalpa]

Great! I am glad it all worked out.
Flytandem,BTW you do know that the fregat and the chapman probe are two separate units and you can use up all the Dv in the fregat hit "j" again and still have tons of Dv in the probe?

Wow, you got all the way there, did all the Sync and Rinc corrections, orbited and LANDED all on the fregats Dv. I am impressed.

 

[flytandem]

:huh: huh?
So I opened up the scenario and hit j and sure enough the thing came apart and as before I switched ships but this time to focus on the probe. And it showed 2972 m/s dv. That would mean that I would have still nearly 4,000 m/s to play with before separating. Maybe another asteroid, if I have the inclination? (pun intended)

We are all different and have different ways of thinking. To me the challenge here is the setting up of the simulator with all the downloads and config files and, ... well I don't even know how to describe it because it's all greek to me. You could give me 100 years and I wouldn't be able to set up that cd you fired off to me. I get so frustrated sometimes... :compbash2: But I've found planning and flying, on the other hand, just so simple. And fun.

I wasted 3 hours one day because user account control (vista) was messing up the way Orbiter was saving scenarios. Then another 3 hours this week wasted because vista wouldn't let me delete a file from the desktop which turned out to be something about taking ownership of the file. And 2 hours just trying to figure out how to run "dosbox" so I could make an old dos program run because vista doesn't talk dos. I am always impressed with the work of the Orbiter developers. Here's to all of you with computer talents...
rob


-----Post Added-----


FLIGHT REPORT
I just had to try an inner-planet sling cascade to hit a trojan with the Chapman so I opted to pick a trojan first and then try to get a direction a timing correct to hit it. It's harder this way but I went for it. I found one that has the following dates.
Depart Earth 56131.94 Pro=-5.721Km Out=0 PlaneChange=711m
Venus MJD56291
Venus MJD58538
Earth MJD59392
Jupiter MJD60059 sling= Out 42.8 Inc 119.7
Trojan=2008 RV119 MJD62471 Encounter Vel 2335 m/s

Had about 400 m/s spare deltaV in the Frigat when orbit insertion was complete. Had't separated the Chapman probe yet.

It was one of the more challenging flights I've done as there was a 6 pass resonant orbit at Venus where I needed to sling on the 1st and 6th, with the 2nd, 3rd, 4th and 5th intentional near misses so as not to be flung off course for that 6th pass. I intentionally went a bit wide on the first sling which allowed the 2nd, 3rd and 4th pass to miss an increasingly greater amount. On the 4th as I crossed the orbit of Venus (now 15G ahead of the planet) I did a prograde burn of about 70 m/s which brought the pass back on queue for a direct sling pass #6. It then slung to Earth and onward to Jupiter. Jupiter did the kick to an inclined orbit to meet up with the Trojan a bit less than 1 orbit later.

I kept all the saves in case anyone wants any of them.

Here's a screen cap after orbit insert.

 

[atuhalpa]

Inclination change sling tutorials?

I have been able to rendezvous with three separate Trojans, but my slings around Jupiter have not been very precise. If it hadn't been for the fregat I would have run out of Delta V. I really don't know how to fine tune the inclination change and the circularization of the subsequent "lap" orbit with any degree of precision. My manuvers are extremely imprecise. They use a wasteful amount of Delta V.

So... I was wondering if Flytandem or Piper could maybe create a short tutorial highlighting the main points of this type of sling. It, at least to my understanding is not really a direct sling and therefore is a bit more involved. I do know the rudiments of direct slings say from Jupiter to Saturn as I have done Flytandem's Voyager flight tutorials.

Flytandem, you stated in an earlier post: "So I opened up the scenario and hit j and sure enough the thing came apart and as before I switched ships but this time to focus on the probe. And it showed 2972 m/s dv." How does one know how much m/s dv a stage or probe has?

 

[tblaxland]

How does one know how much m/s dv a stage or probe has?

I use BurnTimeCalcMFD:
[ame="http://www.orbithangar.com/searchid.php?ID=1407"]BurnTimeCalcMFD (BTC) 1.5[/ame]

 

[Piper]

I have been able to rendezvous with three separate Trojans, but my slings around Jupiter have not been very precise. If it hadn't been for the fregat I would have run out of Delta V. I really don't know how to fine tune the inclination change and the circularization of the subsequent "lap" orbit with any degree of precision. My manuvers are extremely imprecise. They use a wasteful amount of Delta V.

The key to slings such as these, is the time and date you do the swing-by of Jupiter. Ultimately you are trying to get your "longitude of the ascending node" (LAN), to match your target's LAN.

From a mathematical point of view, the best fly-by date of Jupiter is when Jupiter's "True Anomaly" is equal to either the target's LAN, or 180deg from its LAN (ie. the longitude of the descending node).