Author Topic: NEP AG transit to Mars  (Read 53147 times)

Offline JohnFornaro

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Re: RE: NEP AG transit to Mars
« Reply #80 on: 03/26/2009 11:51 pm »
Here's the link to the download area.
http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=1219&start=1 - which is for presentations and video in L2.

Is there a different level of membership?  when I hit this link, I am told it is not for me to view.  Thanks
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Offline Kaputnik

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Re: NEP AG transit to Mars
« Reply #81 on: 03/29/2009 06:15 pm »
Yes, there's the Level 2 area which is subscription only.
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Offline mlorrey

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Re: RE: NEP AG transit to Mars
« Reply #82 on: 04/01/2009 09:48 pm »
For manned missions the ~12 month NEP transit to Mars (versus the commonly quoted 3 months for NTR) is a big disadvantage. I know which one I'd prefer to be on.  NEP certainly has uses in unmanned deep space, like in the original JIMO concept.

Shouldn't the transit be faster than 12 months? I thought it was 6 months each way. A Hohmann transfer should leave Earth when it is opposite (aphelion) from the point in Mars orbit where Mars WILL BE when the craft reaches it, which should occur at conjunction.
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Offline JohnFornaro

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Re: NEP AG transit to Mars
« Reply #83 on: 04/01/2009 10:13 pm »
Figgered out the subscription thing, and am now subscribed...  Thanks, Chris.
Sometimes I just flat out don't get it.

Offline kfsorensen

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Re: RE: NEP AG transit to Mars
« Reply #84 on: 04/01/2009 11:40 pm »
Shouldn't the transit be faster than 12 months? I thought it was 6 months each way. A Hohmann transfer should leave Earth when it is opposite (aphelion) from the point in Mars orbit where Mars WILL BE when the craft reaches it, which should occur at conjunction.

NEP/SEP transfers to Mars have different orbital dynamics than ballistic (high-thrust) trajectories.  Ballistic trajectories leave the departure planet and arrive at the destination planet with significant relative velocities, whereas the EP trajectories leave with little excess velocity and arrive at nearly a matching velocity.  They take longer to fly, but I wouldn't look at this as much of a disadvantage.

Offline mlorrey

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Re: RE: NEP AG transit to Mars
« Reply #85 on: 04/04/2009 06:10 am »
Shouldn't the transit be faster than 12 months? I thought it was 6 months each way. A Hohmann transfer should leave Earth when it is opposite (aphelion) from the point in Mars orbit where Mars WILL BE when the craft reaches it, which should occur at conjunction.

NEP/SEP transfers to Mars have different orbital dynamics than ballistic (high-thrust) trajectories.  Ballistic trajectories leave the departure planet and arrive at the destination planet with significant relative velocities, whereas the EP trajectories leave with little excess velocity and arrive at nearly a matching velocity.  They take longer to fly, but I wouldn't look at this as much of a disadvantage.

Hmm I'm not sure this is entirely accurate. The studies I saw for VASIMR propelled missions to Mars show it actually takes less time than a Hohmann transfer, with the big time waster being crawling out of Earth's gravity well. After that happens it is more or less heading directly for Mars.
http://www.space.com/businesstechnology/technology/vasimr_rocket_020807-1.html
http://nextbigfuture.com/2007/11/vasimr-engines-plus-200-mw-of-nuclear.html
http://dma.ing.uniroma1.it/users/bruno/Petro.prn.pdf

Constant thrust electric propulsion with their high Isp actually attains much higher average velocities than the chemical or other high thrust/short burn, although the real time savings of such methods is more readily seen in missions to the asteroids and beyond.

Getting nuclear reactors into space is the big stumbling block. I am hoping that Lonnie Johnson's JTEC system could provide a zero moving parts solar thermal power plant thats 60% efficient, which would be a much higher power density than PV or nukes.
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Offline Chris Bergin

Re: NEP AG transit to Mars
« Reply #86 on: 04/05/2009 04:09 am »
This thread was taken off course, split it. Keep it on NEP AG transit to Mars from now on, or we'll just delete the posts.
« Last Edit: 04/05/2009 04:10 am by Chris Bergin »
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Offline Kaputnik

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Re: NEP AG transit to Mars
« Reply #87 on: 04/05/2009 02:49 pm »
Does anybody have a good source of information on these EP Mars transfer trajectories? I'm thinking some sort of table of examples showing the transfer times attainable with a certain thrust and isp. I'd imagine it's a much harder thing to calculate than a simple one-impluse Hohmann transfer.
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Offline kfsorensen

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Re: NEP AG transit to Mars
« Reply #88 on: 04/05/2009 04:10 pm »
Does anybody have a good source of information on these EP Mars transfer trajectories? I'm thinking some sort of table of examples showing the transfer times attainable with a certain thrust and isp. I'd imagine it's a much harder thing to calculate than a simple one-impluse Hohmann transfer.
I've done a large number of them.

Offline Lampyridae

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Re: NEP AG transit to Mars
« Reply #89 on: 04/06/2009 03:27 am »
Does anybody have a good source of information on these EP Mars transfer trajectories? I'm thinking some sort of table of examples showing the transfer times attainable with a certain thrust and isp. I'd imagine it's a much harder thing to calculate than a simple one-impluse Hohmann transfer.
I've done a large number of them.

I guess they'd be a lot tougher than patched conics. Do you use CATS? How detailed are the models?
« Last Edit: 04/06/2009 03:28 am by Lampyridae »

Offline GI-Thruster

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Re: NEP AG transit to Mars
« Reply #90 on: 04/06/2009 04:53 am »
Not sure if this is helpful but it's interesting:

http://koti.mbnet.fi/jarmonik/Orbiter.html

Offline kfsorensen

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Re: NEP AG transit to Mars
« Reply #91 on: 11/15/2014 03:32 pm »
A spacecraft like this might be even more suitable for an attempt to visit Ceres. The low gravity of Ceres would play to the strengths of the propulsion technology. I look forward to the information from the Dawn probe on the suitability of Ceres as a future target of exploration.

Offline Proponent

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Re: NEP AG transit to Mars
« Reply #92 on: 11/16/2014 11:20 am »
Does anybody know what the numerical forward-trajectory model (RKF56) is?

Offline kfsorensen

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Re: NEP AG transit to Mars
« Reply #93 on: 11/16/2014 01:28 pm »
RKF56? Runge-Kutta-Fehlberg 5th/6th order method with error estimation.
« Last Edit: 11/16/2014 04:19 pm by kfsorensen »

Offline kfsorensen

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Re: NEP AG transit to Mars
« Reply #94 on: 07/10/2022 03:36 pm »
Here's a first blush at an animation of the concept.  Fuel tanks and engines aren't shown yet, but I hope you like it anyway:


Offline kfsorensen

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Re: NEP AG transit to Mars
« Reply #95 on: 07/10/2022 03:42 pm »
I did a little digging last week and came to realize that this concept goes back much, much further than I thought.  Ernst Stuhlinger was apparently thinking along the same lines with his work in 1957 and also in 1962:





Here's some great work by Nick Stevens on modern renders of these concepts:




Offline Robotbeat

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Re: NEP AG transit to Mars
« Reply #96 on: 07/11/2022 09:36 pm »
Almost 8 years later! Heck of a necro-bump (70 years if you count the original idea you dug up!). I like it it, Sorensen!

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