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I decided to fly to Mars in KSP using a slingshot of Venus to see if I could save fuel. Since Venus is closer to Earth, you need less fuel to get there. When I tested it I used less fuel, but the amount I saved in comparison with going directly to Mars was minor because of the Hohmann effect.

I was just wondering if it would be more practical to do a flyby to Mars using a bit less fuel, or just directly flying to Mars?

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    $\begingroup$ Does this answer space.stackexchange.com/questions/51752/… answer your question ? $\endgroup$
    – Cornelis
    Jun 27 at 7:36
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    $\begingroup$ @Cornelis That is for crewed flights. I was talking just in general. $\endgroup$ Jun 27 at 8:18
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    $\begingroup$ Worth it to who? Depends on the requirements, which is what I was getting at. $\endgroup$ Jun 27 at 14:21
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    $\begingroup$ What is practical for one mission might not be practical for another. You yourself have pointed out that, for example, it makes a difference whether the mission is crewed or not. It depends on the requirements. Your question is insufficiently detailed. $\endgroup$ Jun 27 at 14:31
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    $\begingroup$ All real aerospace projects are requirements driven. Whether something is "practical" cannot be known without knowing what the requirements are. In aerospace, "practical" means "can meet the requirements". $\endgroup$ Jun 27 at 14:33

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It is not practical to use Venus to get to Mars in all but one circumstance.

I searched for Earth-Mars and Earth-Venus-Mars (EVM) trajectories in a 900 day launch period starting Jan. 1st 2024. The EVM trajectories require more $\Delta V$ and more time of flight (transfer time) than the direct Earth-Mars trajectories:

Earth-Venus-Mars dV VS TOF

(Personal work)

Earth-Mars dV VS TOF

(Personal work)

However, there are some Mars arrival dates that become accessible (given a launch constraint of 30 $km^2/s^2$ for example) by using the EVM route:

Mars Arrival Dates EVM

(Personal work, mid 2027 accessible with EVM route)

Mars arrival dates EM

(Personal work, Mars arrival not accessible from end of June to start of November 2027)

So if you needed to arrive at Mars at specific dates (e.g. for colonization/supply ships), then there are times where it is more $\Delta V$ economical to use a Venus flyby.

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    $\begingroup$ Thanks a lot for that. Those charts are really interesting. $\endgroup$ Jun 30 at 6:06
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    $\begingroup$ "there are some Mars arrival dates that become accessible": note that this is why the "short stay" Mars mission proposals include a Venus flyby: it costs more delta-v and takes longer, but gives a launch window in the needed time period. Though that's typically on the return trip, so the long period in freefall doesn't affect their ability to work on the surface...it's not very relevant for probes. $\endgroup$ Jun 30 at 13:03
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    $\begingroup$ What software did you use? $\endgroup$
    – qazwsx
    Sep 23 at 17:52
  • $\begingroup$ @qazwsx see here $\endgroup$ Sep 29 at 23:50
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Are you using mods like RSS/RO or with Principia? If not, then the data is maybe not as accurate compared to real life circumstances. But if it is, I would say doing a simple Hohmann transfer to Mars would be enough, since it requires roughly the same amount of ΔV for Mars and Venus. Venus requires about 2.5 km/s of ΔV and Mars requires 2.9 km/s of ΔV. Of course Venus has much lower budget requirements but I think it would be much less complicated and cost effective for the mission planners and reduces time needed for the mission, and would be hugely impractical for manned missions since the time needed is extended, more resources are needed for the crew to sustain the way to Mars. Therefore, I think it would be impractical unless there are special circumstances for mission requirements.

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