Chapman Challenge

[atuhalpa]

Chapman challenge advanced mission accomplished!

Yeah! Piper I did it all on my own this time. My inclination change for 1996 RJ wasn't as good as it should have been but I had the Fregat along for the ride so I had plenty of Dv. I launched a D4HV from Kourou. After Jupiter encounter and inclination change I crossed 1996 RJ's node about a quarter of the way around, so it cost alot to align the 5 degrees I was off. Syncing cost me about the same as I did sync adjustments frequently. In the end I was 343M distant and had to adjust for a 976 Rvel. I used IMFD's velocity match to close and sync 3 times then I backed into orbit with 60% fuel left in the Chapman.

All in all a most enjoyable and educational experience.

 

[Piper]

Yeah! Piper I did it all on my own this time. My inclination change for 1996 RJ wasn't as good as it should have been but I had the Fregat along for the ride so I had plenty of Dv. I launched a D4HV from Kourou. After Jupiter encounter and inclination change I crossed 1996 RJ's node about a quarter of the way around, so it cost alot to align the 5 degrees I was off. Syncing cost me about the same as I did sync adjustments frequently. In the end I was 343M distant and had to adjust for a 976 Rvel. I used IMFD's velocity match to close and sync 3 times then I backed into orbit with 60% fuel left in the Chapman.

All in all a most enjoyable and educational experience.

Yet again, excellent work! I have to say, I love seeing people complete these challenges, it's nice to know that I'm not the only person who can do this stuff.


By the way, is there anybody else still working on any of the current challenges? If there isn't, I'll bring this one to a close at the end of the month, and start the next one.

Also, how does people feel about using low-thrust engines (ie. ion thrusters like Smart-1)? I'm currently designing a fourth (and maybe fifth) version of Chapman that uses a Hall effect thruster instead of a liquid propellant engine, and if there are enough people out there that are experienced on doing a challenge like that I'll do an advanced challenge with it. It would probably be something straight forward like getting into orbit around Ceres (which I actually did last night with it , after a beautiful fly-by of Mars). Currently the design has a total dV of about 28,000m/s (about 10 times that of the other Chapmans). However that may change as I try and find the most appropriate settings.

Speaking of the next challenges, does anybody have any recomendations? I have some of my own ideas, but I would love to hear some other ones.

 

[astrosammy]

Maybe some challenges with reaching different Lagrange points? Or bring two probes up at once, let them arrive at an planet at different times and let them rendezvouz each other.

 

[Whatu]

Venus challenge:

Finally completed it!

I launched the Chapman in an Ariane 5 ECA from Cape Canaveral, but I didnt take a pic of it, sorry.
With about 98% fuel of upper stage, I executed my escape plan (transx):

hm.. I need to learn a little bit more in this area, transx approximation was 12 M.. way off.

Necessary correction (IMFD from now on):

After capture burn:

One of the aerobrakes:

I did the first aerobrake at ~0.01 g's to get the taste of it, and after that I did 5 or 6 ~0.4 g's ones.

Last aerobrake:

To finally circularize at ~550km. 45º ecliptic inclination.


So, thanks to you Piper for providing such an enjoyable and educative challenge.

I will try to at least get to a Trojan, but not for this challenge, because this can take ages!

Looking forward to the new challenges and maybe a little tutorial on low-trust navigation.

 

[atuhalpa]

Piper's website

Wow Piper, I just went to your website for the first time. I didn't know how much you had contributed till I went there. I must say I am awestricken by how much you have done regarding all aspects of Orbiter. I feel like a toddler after seeing your accomplishments. By the way thanks for the Chapman Challenge II recognition.

The only negative aspect of my involvement in the Challenge and Orbiter is that my live in girlfriend has threatened to leave me if I spend much more time hunkered down in front of the transx console grunting 'No!' back at her when she asks me if I coming to bed yet :blackeye:.

I guess I'll just have to get HER interested in Orbiter as much as I am.

 

[Piper]

Last chance for anyone still working on either of the challenges, if there isn't anybody still working on them, I'll began the third challenge.

 

[atuhalpa]

Next challenge

Ceres orbit with a hall thruster sounds good. BTW Ceres is at opposition on February 25th @ 9 AM EST.

 

[mjanicki]

Third challenge! I can't wait.

As for suggestions, I remember taking a trip to 216 Kleopatra (from the Asteroid Pack addon) about a year ago, but using a Deltaglider with unlimited fuel. I would be interested in a challenge that involved that main belt asteroid and one of the Chapman probes.

 

[flytandem]

Speaking of the next challenges, does anybody have any recomendations? I have some of my own ideas, but I would love to hear some other ones.

How about a challenge of sending the Chapman to do a flyby of as many planets as possible? Start from any reasonable transfer burn from Earth to any starting planet, the only requirement would be to only use the Chapman engines after that initial transfer burn. The reason I suggest going to the planets is that, try as I might, I still have no clue how to add additional rocks.

 

[atuhalpa]

Flytandem, did you try installing Piper's Trojans zip pack?

 

[flytandem]

Flytandem, did you try installing Piper's Trojans zip pack?

I've spent at least 5 separate 1 hour periods trying to get anything related to this series of challenges to run. Just now I once again started with a vanilla Orbiter package and thought I followed all instructions regarding getting a chapman probe to run yet still it does a ctd an all scenarios. I also have tried to make sense of that app to install asteroids but it won't respond and I must start task manager to shut that app down. Regarding the probe ... perhaps files aren't in their correct folder but it's way beyond me. The base package runs fine and there are plenty of challenging tasks just using the deltaglider on low fuel. To me what actual craft is being navigated is arbitrary. The challenge is navigating. And if the destinations aren't being seen there's no way to navigate to them.

 

[mjanicki]

I, for one, really appreciate all the navigational insight you've brought to this thread, Flytandem. So if you want to have another go at getting some of the launchers and probes working I'm sure we can all try to help.

I know that when I wanted to use the Atlas V it needed LC41 which was developed for an older version of orbiter. I had to change the configurations because I too was getting CTDs (hence why I never managed to get the first challenge done). But I figured out how to get LC41 working on my system. I think a lot of the pre-fab scenarios launch from LC41 so that could be a source of your problems. I'd be happy to post what I did to get it all working if you think it might help.

-- Mike

 

[flytandem]

Here's a question. Would it be possible to start a scenario using a stock deltaglider just to get a low earth orbit and transfer burn completed and do a save just after the burn in done. Then edit the scenario to change the deltaglider into a chapman probe and do the remaining flight and mid course corrections using the probe? Basically, forego the hassles of setting up the staged rockets. I tried to do this a bit ago and even this failed miserably. Maybe it's not even possible. I've done this in the past switching a deltagliderIV into a deltaglider just to make spacecraft operation simpler so I can concentrate more on navigation.

A navigational challenge I am currently playing with would be to start Earth some time between late 60s and early 70's to do 1 transfer burn that slings Venus with an energy losing sling, then does a fly-by at Mercury then with energy boosting slings uses Venus, Earth and Mars to be in place to hit Jupiter for the Voyager tour. I know it must be possible, it's just a matter of finding it. Like finding a gold nugget in a stream. Once found it would be a single burn that does a flyby at ALL the planets using only minimal DV along the way.

edit: so far I have Jan 1971 depart, to Venus, Mercury, Venus, Venus, Venus, Earth, Mars, Earth and it takes me out past Jupiter orbit in the correct place where Jupiter would be for the voyager mission through outer planets but... arrived 2 years too late at Jupiter orbit so Jupiter is out of phase,.. ugh. Either need to start in 1969 with similar slings or make slings more energetic to reduce number of slings.

 

[atuhalpa]

Flytandem, do you have a prefered real world launch platform?

 

[flytandem]

Flytandem, do you have a prefered real world launch platform?

No. Actually the letters NA might answer the question more appropriately.
I prefer to use a real world dv budget to plan missions, but simplify the actual execution of the mission by using a stock deltaglider with reduced fuel. For example, after reaching LEO I usually try to have an entire transfer and MCC dv well under 5K m/s. If there were a simpler craft than the stock DG that's what I would use. To me the power of Orbiter is not in craft creation but rather in navigational creativity. There are a lot of free rides out there for the taking.

 

[Piper]

No. Actually the letters NA might answer the question more appropriately.
I prefer to use a real world dv budget to plan missions, but simplify the actual execution of the mission by using a stock deltaglider with reduced fuel. For example, after reaching LEO I usually try to have an entire transfer and MCC dv well under 5K m/s. If there were a simpler craft than the stock DG that's what I would use. To me the power of Orbiter is not in craft creation but rather in navigational creativity. There are a lot of free rides out there for the taking.

Sorry, but I don't want people using a stock Deltaglider, since it isn't just about dV. Using a Deltaglider would take away the difficulty of launching with a real-world launcher, and the deltaglider has much different thrust characteristics then a Chapman probe.

When you unzip the files for the chapman probe, do all the files end up in a single folder, or do they go into seperate ones?

 

[atuhalpa]

Flytandem, if you had had a launch platform that you preferred I was going to create an orbiter install that had your preferred platform and all the trojans and the chapmans and everything that was required and that ran just perfectly on my machine and then burn it to disc and send it to you. That might fix the problem?!?!

 

[flytandem]

Flytandem, if you had had a launch platform that you preferred I was going to create an orbiter install that had your preferred platform and all the trojans and the chapmans and everything that was required and that ran just perfectly on my machine and then burn it to disc and send it to you. That might fix the problem?!?!

Wow. That's a very generous offer. Since I know nothing about launch platforms (I usually hit control + to begin rolling and * for meco) if you want to do it that would be appreciated. So it's your call on which platform. Simple is good however.

The latest effort to get an enhanced grand tour flightplan with slings off all planets has me going from completing inner planets finally slinging Earth toward Jupiter, but it hits Earth at the Earth/Jupiter window 13 months after the famed summer '77 voyager window. The fun thing about this stuff is that such a miss is so huge that it means starting all over with a completely new launch date. To me this is pure fun not frustration. Having a pile of files that are perhaps all in the wrong place is what is frustrating.

my www.flytandem.com website has my mailing address on the contact page if you are still keen on sending me a disk.

thanks
rob


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

Sorry, but I don't want people using a stock Deltaglider, since it isn't just about dV. Using a Deltaglider would take away the difficulty of launching with a real-world launcher, and the deltaglider has much different thrust characteristics then a Chapman probe.

When you unzip the files for the chapman probe, do all the files end up in a single folder, or do they go into seperate ones?

The files are in separate folders. Winzip has a checkmark to use folder structure. Files in the wrong place is just a guess on my part. I've no idea why it won't run. Plus getting that app to run to install asteroids is a consistent lockup of the system and there's no response to the program at all, needing task manager to terminate the app. Maybe it's a Vista thing.

I admit that getting an addon launcher to run is a challenge. It's a challenge in how to arrange and edit configuration files but has nothing to do with how current real world rockets are launched. However, basic flight planning is using orbital mechanics the same as (though less precise than) real world space flight. Isn't this the real challenge of Orbiter?

Once the files are correctly in place, or whatever is needed to allow the sim to run, is the rocket launch done completely manually or is it automated to some extent like I've seen on the Apollo AMSO addon? Is an automated launch a challenge? What acceleration does the Chapman Probe have BTW? I assume it has some sort of on-board thrust and a way to rotate itself. And how much DV? Since the DG is completely manually flown and when using TransX for guidance it is manually oriented for all burns. Isn't this a challenge?

Actually, if there were a craft that had no visible shape at all, just a glass cockpit, to be able to fire up a couple of copies of TransX, with a little bit of ROT fuel and a way to thrust it would 100% satisfy me.

 

[atuhalpa]

Ok, I'll set up a Delta 4HV with a fregat and chapman probe. It will be a CVEL platform and I'll set up a scenario template that you can modify easily for MJD, launch location, and specific chapman probe.

I like to launch manually. I have been using the D4HV long enough now that I can get into LEO at 220km with less than .5 degrees Rinc and still have 95% fuel left in the earth eject stage. Just remember that the eject stage is cryogenically cooled and if you don't use your fuel you lose it soon after ejection.

 

[flytandem]

Thanks Atuhalpa.
BTW I just managed to find a solution to an enhanced grand tour. It's a voyager outer planet finish but starts several years earlier with inner planet slings so it visits ALL planets. It has an almost identical initial transfer burn as the Voyager missions, which is pretty energetic considering it's only heading to Venus but it does the trick.

In planning it, after several inner slings TransX was becoming unstable so I did a little trick that's sometimes needed... the Cl App was wandering around at the 41696 Venus encounter (see data below) leaving me unable to adjust slings after that encounter, so when it was close I looked at the date and encounter velocity and then turned off inherit velocity and entered the date and velocity manually. Then it stabilized and allowed continuing sling planning to what ultimately was a 25 stage flightplan. Data is as follows...

Depart Earth Jan 16, 1968, MJD=39871.6808, Pro=-7.903Km, Out=-3.887Km, PlaneCh=-714.5m
Slings with MJD dates are as follows...
Venus 40000
Mercury 40212
Mercury 40476
Venus 41349
Mars 41522
Venus 41696
Venus 42237
Earth 43297
Jupiter 44126
Saturn 44952
Uranus 46687
Neptune 48097
...

The reason I searched this sling cascade is that this thread is about real world sims and using a craft that supposed to be limited to current day technology. Yes this flight is an after the fact "what if" but it's not unreasonable to say "what if the voyager planetary alignment concept had been noticed earlier" and was set up to include an inner planet enhancement of which this is just an example. In any event it would surely be a challenge to fly this mission no matter what craft you use. The goal would be to limit the total MCC corrections to a minimum because there are probably going to be quite a few with 12 slings on the menu. To sim real life it would just need a craft that can handle 22 years of exposure to the space environment. Since the Voyager is still with a pulse (i think) I suppose that's within real life too.


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


I just flew the enhanced Voyager mission and have some observations to make. The dates mentioned above are fairly accurate with regard to the inner planets but it actually came closer to the real Voyager mission than predicted for the outer planets. The arrival dates at each planet are as follows...
Venus 40000 (as predicted)
Mercury 40212 (as predicted)
Mercury 40476 (as predicted)
Venus 41349 (as predicted)
Mars 41518 (4 days ahead of plan)
Venus 41696 (as predicted)
Venus 42237 (as predicted)
Earth 43297 (as predicted)
Jupiter 44046 (in between the two Voyager missions)
Saturn 44952 (in between the two Voyager missions)
Uranus 46416 (6 weeks ahead of the Voyager mission)
Neptune 47715 (3 weeks ahead of the Voyager mission)

The mission was completely free coasting with no deep space maneuvers but there were on average something like 25 m/s per sling corrections for the inner planets and about 55 m/s per sling for the outer planet planet slings. The total dv used for all slings from the initial transfer from Earth to passing Neptune was 405 m/s. Not bad for 12 slings in all. The initial transfer burn was 6336 m/s from LEO.