Chapman Challenge

[flytandem]

What was your encounter velocity with the asteroid after you flew by Jupiter? Were there any maneuvers between Jupiter and the asteroid?

edit: The reason I ask is that I don't have a copy of the asteroid orbit you chose and have no idea what you will need to do (how much dV) after Jupiter to rendezvous with the asteroid. Just can't seem to get the asteroid utility (MPCORB) to run.

 

[tblaxland]

Ooops, forgot to ask. I noticed that Patroclus is invisible. It's there as a target for TransX but if I'm parked next to it in a DG.... there is nothing visible. Probably missing some file(s).

I must admit I've never checked it at my end. Perhaps the texture file is missing/in the wrong spot. Asteroid4.dds should be in your Orbiter/Textures folder.

Here's the scenario that I used to do the advanced challenge. You launch aboard an Atlas V (552). The asteroid is called "2001 DZ3" and you will need the MPC Database Viewer and Exporter to get it. Because there is a space in the name, you will need to re-target 2001 DZ3 once you start it up.
...
The key for picking a good Trojan to orbit, is to pick a "leading" Trojan, one that is 60deg ahead of Jupiter as opposed to following it. Also, you need to swing-by Jupiter along one of the Trojan's nodes, otherwise the Trojan won't be there when you come back around the sun.

So my choice, Hektor, should work equally well. The Delta IVH should have enough dV to get me there too. Thanks for that

 

[flytandem]

I had the right idea of hitting Jupiter as it crosses a node of an asteroid. I did it by trying to sling off the inner planets. It's tough enough to get a series of slings to work that gets the final sling up to Jupiter orbit to be where Jupiter is at that time, but to require that Jupiter is also at a specific spot (a node) is much tougher. And then to have the arrival speed fairly slow adds more difficulty still. Here's a lengthy flight that has at least 3100 less m/s for the initial transfer than going to Jupiter directly. Lots of tweaking to get it this far. It arrives at a node for Patroclus. The arrival speed to Jupiter is a bit higher than desired but not terrible, and given the initial savings of over 3100 m/s it could be an interesting way to get there. Since I don't have the rocket boosters it's displayed with a stock DG for simplicity. TransX 3.13.

BEGIN_DESC
Earth to Venus, Venus, Earth, Jupiter, Patroclus
END_DESC

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  System Sol
  Date MJD 56592.2023761574
END_ENVIRONMENT

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  FOV 60.00
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  Vector  4942419.88501 1754217.49728 3617320.5304
  Vector  -191.087578017 -143.423409053 330.640010749
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  MODE TransX
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END_PANEL


BEGIN_SHIPS
3:DeltaGlider
  STATUS Landed Earth
  POS -80.6858943 28.5906644
  HEADING 330.02
  RCSMODE 0
  PRPLEVEL 0:0.466 1:0.100
  NAVFREQ 0 524 84 114
  XPDR 6
  GEAR 1 1.0000
  PSNGR 2 3 4
  TRIM 1.000
END
END_SHIPS

 

[Piper]

Chapman Challenge II

Ok, I've finally posted the results of the first Chapman Challenge, and the second one has officially begun. Since there is a lot of interest in the advanced part of the first challenge, I've included it in this one for the advanced challenge. Good luck!

End date: February 15th, 2009

Regular Challenge:

• Mission Goal: Venusian Orbit​
  • Bonus: Use Aerobrake MFD to then bring yourself into a circular orbit​
• Spacecraft: Chapman Inner-1​
• Launch Location: Your Choice​
• Launch Vehicle: Your Choice​
• Launch Window: 55562.0000 and onward - Anytime after January 1st 2011​

Advanced Mission:

• Mission Goal: Swing-by Jupiter, then orbit a Jupiter Trojan asteroid​
  • Bonus: Use one or more slingshots to get to Jupiter​
• Spacecraft: Chapman Outer​
• Launch Location: Your Choice​
• Launch Vehicle: Your Choice​
• Launch Window: 55562.0000 and onward - Anytime after January 1st 2011​
• Required Add-ons:​
  • [ame="http://www.orbithangar.com/searchid.php?ID=1436"]MPC Database Viewer/Exporter[/ame] by Joseph Morgan​

 

[flytandem]

What a fun challenge Piper! (the first advanced one, just noticed you posted the next while I was making this post) Even without the designated craft, the navigation thought process has taught me a lot. I would like to know the allowable total deltaV of the craft because at least from a navigation challenge I would know if the TransX plan I am setting up is within limits.

And a quick disclaimer... I don't really have any technical background in this stuff. All I have is what Orbiter is showing me so take this stuff with a grain of spacedust. :lol:

I found another inner sling but this one hits the Hektor node. Here's the code for the stock DG so you could paste the TransX part into whatever ship you are working with. It has a soft (minimal) encounter speed at Jupiter.

I mentioned in a previous post about how TransX can inadvertantly "slip" the Orbits to Icept value down while playing with sling angles. Even just loading a plan this can happen. This is an example. So when opening it up you will probably need to go and check that Stage 6 has Orbits to Icept = 1.5
Also notice the last sling has a manually set sling speed. (inherit velocity = "no"). I rambled about that below the code.

BEGIN_DESC
Leave Earth for slings of Venus, Venus, Earth, Jupiter then rendezvous at Hektor. Make sure that in stage 6 the Orbits to Icept value is 1.5.  The Jupiter sling is a manually set sling speed so there will be a burn needed at the Pe of the sling. 
END_DESC

BEGIN_ENVIRONMENT
  System Sol
  Date MJD 55562.1063817245
END_ENVIRONMENT

BEGIN_FOCUS
  Ship 3
END_FOCUS

BEGIN_CAMERA
  TARGET 3
  MODE Cockpit
  FOV 60.00
END_CAMERA

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  Handle Hektor
  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 1
Prograde vel.
 0  0
Man. date
 0  55562.0995657
Outward vel.
 0  0
Ch. plane vel.
 0  0
Intercept with
0 0
Orbits to Icept
0 0
Graph projection
0 0
Scale to view
0 0
Advanced
0 0
Draw Base
0 0
Finvars
  Finish BaseFunction
END_MFD

BEGIN_MFD Right
  TYPE User
  MODE TransX
END_MFD

BEGIN_PANEL
END_PANEL


BEGIN_SHIPS
3:DeltaGlider
  STATUS Landed Earth
  POS -80.6858943 28.5906644
  HEADING 330.02
  RCSMODE 0
  PRPLEVEL 0:0.466 1:0.100
  NAVFREQ 0 524 84 114
  XPDR 6
  GEAR 1 1.0000
  PSNGR 2 3 4
  TRIM 1.000
END
END_SHIPS

BEGIN_ExtMFD
END

The encounter speed (the sling speed) is used in the sling to compensate mostly the change in plane (which is why we encounter at a node) and to either provide a bit slower or faster than jupiter's orbital speed to allow the next orbit to synch up with the asteroid. If the asteroid has a small difference in the inclination to Jupiter there is a problem. The sling either overcompensates for the plane change or the plane change is correct but the resulting orbital speed is very different than the asteroid meaning the difference must be compensated by using some engine deltaV.

Tblaxland provided me a couple of asteroid to look at, Patroclus and Hektor. Both of these have about 20 degrees inclination (one is 18 and the other 22) relative to Jupiter. Given Jupiter going about 13.5 Km/sec an inclination of 20 degrees gives something like 4.3 Km/sec speed that the asteroid is crossing Jupiter orbit. Even going directly to Jupiter so the minimum encounter is 5.6 Km/sec it means that one would have to swing the sling inclination angle around to such a high value that is will cause a lot of slowing of the orbit and a fairly large engine burn would be needed during the sling to change the sling speed.

By going directly to Jupiter you can have a minimum Jupiter encounter of about 5.6 km/s. If you sling from inner planets the minimum is probably more like 6.7 km/s. But the initial savings of 3 km/sec doing inner slings means it's a net gain of 1.9 km/sec.

The scenario to go to Hektor (above) has an encounter speed at Jupiter of about 6.7 Km/sec. I manually set the sling speed at 4.6 Km/sec. This allows both a plane change and a nice speed to synch up in 1 orbit. But it means a burn of about 2.1 km/sec during the sling (maybe a bit less since it's in the gravity well). So just choosing Hektor means no choice but a needed burn in the sling of 2.1 Km/sec if you come from inner planet slings and 1 km/sec if you come directly from the Earth.

 

[T.Neo]

Mission Goal: Venusian Orbit

Seems easy. I might give it a try.

EDIT:
1st attempt failed. I need to learn how to Aerobrake.

 

[tblaxland]

I would like to know the allowable total deltaV of the craft because at least from a navigation challenge I would know if the TransX plan I am setting up is within limits.

You could use the dV budgets I posted earlier as a guide. Since the launch vehicle is not specified, the dV for Earth departure is somewhat variable.

To eject from LEO (250km x 250km)
Ariane 5 ECA - 4.5km/s
Delta IVH - 9.8km/s

All other maneouvres:
Chapman Probe - 2.97km/s

The scenario to go to Hektor (above) has an encounter speed at Jupiter of about 6.7 Km/sec. I manually set the sling speed at 4.6 Km/sec. This allows both a plane change and a nice speed to synch up in 1 orbit. But it means a burn of about 2.1 km/sec during the sling (maybe a bit less since it's in the gravity well). So just choosing Hektor means no choice but a needed burn in the sling of 2.1 Km/sec if you come from inner planet slings and 1 km/sec if you come directly from the Earth.

So it seems I need to choose better targets, ie, with lower relative inclination to Jupiter's orbit. I'll see what I can find. I doubt that using that much dV during a Jupiter flyby would leave enough for orbit insertion at the trojan.

 

[flytandem]

You could use the dV budgets I posted earlier as a guide. Since the launch vehicle is not specified, the dV for Earth departure is somewhat variable.

To eject from LEO (250km x 250km)
Ariane 5 ECA - 4.5km/s
Delta IVH - 9.8km/s

All other maneouvres:
Chapman Probe - 2.97km/s


So it seems I need to choose better targets, ie, with lower relative inclination to Jupiter's orbit. I'll see what I can find. I doubt that using that much dV during a Jupiter flyby would leave enough for orbit insertion at the trojan.

Thanks. I asked because Piper had something like 7100 m/s needed for the transfer to Jupiter so even if both the Ariane and Chapman were fired up for that transfer it left very little for a combination of MCC and the necessary braking burn when approaching the asteroid.


And regarding choosing which asteroid, it's having too LITTLE inclination that makes it tough. There is no way to encounter Jupiter less than about 5.6 km/s if hohmann from Earth and probably about 6.7 km/s if coming from slings. This speed has to go somewhere when leaving Jupiter. If it's not put into an inclination change then it has to go to in/outward or pro/retrograde changes. Given that the asteroids are very much like Jupiter other than some inclination, a bit of pro/retro to help synch in the next orbit is good but the rest has to change plane. 20 degrees isn't enough I think so maybe there are some rocks with more inclination rel to Jup... Thanks for Patroclus and Hektor. I still can't figure out a way to get the other asteroids into my orbiter folder so other than helping with some advice on a TransX sling plan I'm not able to get involved any further.

What I would do if I had the asteroids would be to start with a DG sitting on Jupiter and play with a TransX escape plan using a sling... (escape, autoplan=off, plan=sling direct, velocity about 7,000 m/s). Then pick each asteroid as a target one at a time and with each advance the sling date to the node and play with inclination sling angle only and perhaps massage a bit of change with velocity to see if it can get an in plane trajector with synching after one orbit. Then I would know which rock could work with about that much velocity and it would then be the task of starting the inner planet slings to send the ship to that point in Jupiter's orbit, when Jupiter is there with about that much encounter speed.

rob

 

[astrosammy]

I think I found a nice solution to swing around Jupiter to Odysseus, but as this is my first slingshot (Ok, I made some free-return flights around moon, but that is easy) I could end outside the solar system. A Delta IV Heavy with 6 additional SRBs and an Fregat upper stage made it possible to fly directly to Jupiter. The slingshot will happen at 57644.7474. I'll go back to Orbiter now an see if I planned it right and arrive in Orbit.

EDIT: Ok, I think I first have try easier slings, I ended up in strange solar orbit after burning nearly all the fuel at Jupiter. I'll try the new Venus challenge now.

 

[tblaxland]

Thanks. I asked because Piper had something like 7100 m/s needed for the transfer to Jupiter so even if both the Ariane and Chapman were fired up for that transfer it left very little for a combination of MCC and the necessary braking burn when approaching the asteroid.

Which is why I gave the Delta IVH option with 9.8km/s. Piper was using an Atlas 552. I can't get that launch vehicle working (problem with Vinka's multistage, as far as I can tell...) but looking at its specs on Wikipedia it should have the required 7.1km/s for Earth departure. Technically, I can't see any issues launching on a Delta IVH, but in the real world it might be more cost effective to launch on one of the smaller boosters.

And regarding choosing which asteroid, it's having too LITTLE inclination that makes it tough.

Ah, thanks for clarifying that. Just a thought, would a flyby of Mars help reduce the encounter velocity by raising the trajectory periapsis? If I understand it correctly, the high encounter velocity comes from having an orbit periapsis at about 1AU (or less for the VVE trajectories). What about an E-M-J-Trojan trajectory? If you use the Delta IVH, 9.8km/s should be enough dV for the Earth departure.

A Delta IV Heavy with 6 additional SRBs and an Fregat upper stage made it possible to fly directly to Jupiter.

That is a lot of delta-V! The second stage of the Delta IVH should be enough to get you a direct flight to Jupiter without the SRBs and Fregat.

Having said that, I like the idea of adding a Fregat upper stage (should give about 3.3km/s dV by my calcs) but I do wonder what the net benefit would be once you take into account the dV penalty on the Delta IVH.

EDIT: I'm pretty sure the Delta IVH configuration won't allow the addition of SRBs in real life.

 

[Zachstar]

This sounds like a job for Velcro!

Tblax for your Atlas rocket issues have you considered this addon? [ame="http://www.orbithangar.com/searchid.php?ID=3462"]Velcro EELVs v1.02[/ame] It has all the Atlas V versions.

 

[tblaxland]

This sounds like a job for Velcro!

Tblax for your Atlas rocket issues have you considered this addon? http://www.orbithangar.com/searchid.php?ID=3462 It has all the Atlas V versions.

Sweet! Thank you, I had forgotten about that addon.

 

[Zachstar]

BTW flytandem if you want some DV you ought to try to Velcro Centaur G attached to shuttle. It packs QUITE a push (It was designed to put interplanetary probes on faster routes instead of many slingshots) And you get to land the shuttle afterwards!

You can find it in the Velcro base pack [ame="http://www.orbithangar.com/searchid.php?ID=3388"]Velcro Rockets v1.1[/ame]

It uses the default shuttle so I suggest either tinkering to fit it to David's suttles or use launch MFD.

 

[Piper]

...Piper was using an Atlas 552. I can't get that launch vehicle working (problem with Vinka's multistage, as far as I can tell...) but looking at its specs on Wikipedia it should have the required 7.1km/s for Earth departure. Technically, I can't see any issues launching on a Delta IVH, but in the real world it might be more cost effective to launch on one of the smaller boosters....

All the addon's that use Vinka's multistage have the same problem after the 1st stage seperation: Their rotational thrusters (and namely "Kill Rotation") don't work properly. The trick to fix this, is immediately after the 1st stage seperation, do a quicksave, quit, and then restart from either the quicksave, or from "Current state."

It's a pain doing it like that (especially with the time it makes you waste reloading orbiter), but it does allow you do use the smaller, more efficient, launchers.

I haven't used Velcro rockets yet, but I think I'm going to take a close look at it, and see if I can adapt some of the multistage2.dll launchers I typically use to it. If I can get it to work, I'll also check with the original designers to see if I can release the new Velcro ones.

 

[T.Neo]

I haven't used Velcro rockets yet, but I think I'm going to take a close look at it, and see if I can adapt some of the multistage2.dll launchers I typically use to it. If I can get it to work, I'll also check with the original designers to see if I can release the new Velcro ones.

I am currently using a Velcro Delta IVH in my futile attempts to get to Venus.
Velcro rckets can suddenly light up during high time accel, though, and there are other problems with them too.

Just tried the Venus challenge again. Last time I got 300km above Venus, this time I miss Venus by about 700M. Maybe I am too stupid for this .

 

[mbartley]

I just flew Chapman into eccentric polar Venus orbit. I used IMFD for navigation and set an off-plane transfer to launch at about 55998.2 and arrive at Venus at about 56171.0.

I launched on an Atlas V 401. I screwed up and launched into the wrong azimuth, but the Atlas V upper stage still had plenty of delta-V to send me to Venus without using Chapman's engines! I think I'll try this again with Soyuz or Falcon 9.

Chapman reached Venus' SOI at 56170.137 with 98.4% fuel remaining after course corrections. I was approaching Venus with an inclination of 90 degrees, periapsis of 600 km, and PeV of 11.1 km/s.

I used IMFD's delta-V program to do a 2.6 km/s orbital insertion burn, which left me with 9.1% fuel remaining, with eccentricity 0.488 and periapsis of 564 km. MJD 56170.453.

I tried lowering my periapsis to around 125 km for aerobraking. I hold a 90 degree angle of attack, but if altitude is much lower than this, there is a strong aerodynamic torque that flips Chapman into a useless near-zero drag orientation. As it is, I use up some RCS fuel to hold that attitude, and it doesn't look like I'll have enough to do enough aerobraking passes to change my orbit much, unless I do dozens of them.

 

[Piper]

I just flew Chapman into eccentric polar Venus orbit. I used IMFD for navigation and set an off-plane transfer to launch at about 55998.2 and arrive at Venus at about 56171.0.

I launched on an Atlas V 401. I screwed up and launched into the wrong azimuth, but the Atlas V upper stage still had plenty of delta-V to send me to Venus without using Chapman's engines! I think I'll try this again with Soyuz or Falcon 9.

Chapman reached Venus' SOI at 56170.137 with 98.4% fuel remaining after course corrections. I was approaching Venus with an inclination of 90 degrees, periapsis of 600 km, and PeV of 11.1 km/s.

I used IMFD's delta-V program to do a 2.6 km/s orbital insertion burn, which left me with 9.1% fuel remaining, with eccentricity 0.488 and periapsis of 564 km. MJD 56170.453.

I tried lowering my periapsis to around 125 km for aerobraking. I hold a 90 degree angle of attack, but if altitude is much lower than this, there is a strong aerodynamic torque that flips Chapman into a useless near-zero drag orientation. As it is, I use up some RCS fuel to hold that attitude, and it doesn't look like I'll have enough to do enough aerobraking passes to change my orbit much, unless I do dozens of them.

Excellent job! I know you can do it with a Soyuz (it's the one I typically use for going to Mars or Venus), but when I tried doing it with the Falcon 9, I didn't have enough fuel left for an orbit ejection burn, however that may be because I'm not as familiar with launching with Falcon 9 then I am with Soyuz or Atlas.

As for Aerobraking, since Chapman isn't exactly designed with Aerobraking in mind, you would have to do dozens of aerobraking passes anyways (kind of like the Magellan probe did).

 

[Zachstar]

Unless the falcon 9 you are using had another stage it is near impossible to get any meaningful mass outside GEO.

You need a pusher stage. Atleast a star motor.

 

[flytandem]

Ah, thanks for clarifying that. Just a thought, would a flyby of Mars help reduce the encounter velocity by raising the trajectory periapsis? If I understand it correctly, the high encounter velocity comes from having an orbit periapsis at about 1AU (or less for the VVE trajectories). What about an E-M-J-Trojan trajectory? If you use the Delta IVH, 9.8km/s should be enough dV for the Earth departure.

Yes, a flyby of Mars in the last climb to jupiter would raise the Pe softening the encounter a little bit. But I would bet that I could spend a lot of time clicking TransX and not find a solution that has Mars on the last climb to Jupiter. There isn't much kick from Mars as well. I think it's best to appreciate the 3100 m/s savings of doing inner slings and as they say... take the money and run.

I can see there is a lot of interest out there in the assembling of different rockets (addons) in Orbiter. Kuddos to all. My interest isn't in trying to simulate real life current technology. But I do really enjoy trying to minimize deltaV in trajectories. So to whatever extent I can enjoy these challenges just by taking part in the figuring out trajectories, I will. However, if it is going to at all be associated with the actual posted challenge, I would need to know the deltaV limits. So it would be really cool if the challenge posted the limits. Or maybe those that are familiar with the rockets could let me know what the limit is.

Also... anyone out there able to offer advice on how to get the Trojan asteroids into a copy of Orbiter. I can't get that 41 meg download to run. Or maybe I should just wait till a challenge is posted that uses the stock Orbiter planets.

 

[tblaxland]

Yes, a flyby of Mars in the last climb to jupiter would raise the Pe softening the encounter a little bit. But I would bet that I could spend a lot of time clicking TransX and not find a solution that has Mars on the last climb to Jupiter. There isn't much kick from Mars as well. I think it's best to appreciate the 3100 m/s savings of doing inner slings and as they say... take the money and run.

I intend to! I didn't mean for you do spend hours trying to find a trajectory, I was merely raising a hypothetical to check that my understanding of the orbital mechanics.

Also... anyone out there able to offer advice on how to get the Trojan asteroids into a copy of Orbiter. I can't get that 41 meg download to run. Or maybe I should just wait till a challenge is posted that uses the stock Orbiter planets.

There are so many of them there would really be a practical way, unless someone packaged up a bunch of config files like I did for you earlier, except bigger. MPCORB also gives you access to a whole bunch of other interesting objects to fly to.