NEP AG transit to Mars

[JohnFornaro]

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

[Kaputnik]

Yes, there's the Level 2 area which is subscription only.

[mlorrey]

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.

[JohnFornaro]

Figgered out the subscription thing, and am now subscribed...  Thanks, Chris.

[kfsorensen]

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.

[mlorrey]

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.

[Chris Bergin]

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.

[Kaputnik]

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.

[kfsorensen]

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.

[Lampyridae]

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?

[GI-Thruster]

Not sure if this is helpful but it's interesting:

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

[kfsorensen]

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.

[Proponent]

Does anybody know what the numerical forward-trajectory model (RKF56) is?

[kfsorensen]

RKF56? Runge-Kutta-Fehlberg 5th/6th order method with error estimation.

[kfsorensen]

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:

[kfsorensen]

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:

[Robotbeat]

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!