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Old 01-06-2009, 04:54 PM   #46
T.Neo
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Mission Goal: Venusian Orbit
Seems easy. I might give it a try.

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

Last edited by T.Neo; 01-06-2009 at 06:20 PM.
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Old 01-06-2009, 07:03 PM   #47
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Originally Posted by flytandem View Post
 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

Quote:
Originally Posted by flytandem View Post
 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.
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Old 01-06-2009, 07:42 PM   #48
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Originally Posted by tblaxland View Post
 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
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Old 01-06-2009, 09:06 PM   #49
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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.

Last edited by astrosammy; 01-06-2009 at 09:53 PM.
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Old 01-06-2009, 10:47 PM   #50
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Originally Posted by flytandem View Post
 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.

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Originally Posted by flytandem View Post
 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.

Quote:
Originally Posted by astrosammy View Post
 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.
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Old 01-07-2009, 01:42 AM   #51
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This sounds like a job for Velcro!

Tblax for your Atlas rocket issues have you considered this addon?
Velcro EELVs v1.02
It has all the Atlas V versions.
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Old 01-07-2009, 03:16 AM   #52
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Originally Posted by Zachstar View Post
 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.
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Old 01-07-2009, 06:22 AM   #53
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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
Velcro Rockets v1.1


It uses the default shuttle so I suggest either tinkering to fit it to David's suttles or use launch MFD.
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Old 01-07-2009, 03:16 PM   #54
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Originally Posted by tblaxland View Post
 ...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.
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Old 01-07-2009, 04:06 PM   #55
T.Neo
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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 .
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Old 01-07-2009, 09:01 PM   #56
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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.
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Old 01-08-2009, 12:13 AM   #57
Piper
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Originally Posted by mbartley View Post
 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).
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Old 01-08-2009, 02:24 AM   #58
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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.
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Old 01-08-2009, 04:29 AM   #59
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Originally Posted by tblaxland View Post
 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.
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Old 01-08-2009, 05:12 AM   #60
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Originally Posted by flytandem View Post
 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.

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Originally Posted by flytandem View Post
 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.
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