5

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?

The Rocket fan
  • 5,580
  • 3
  • 26
  • 62
  • 3
    Does this answer https://space.stackexchange.com/questions/51752/why-is-there-currently-so-little-talk-about-a-venus-gravity-assist-for-a-crewed/51753#51753 answer your question ? – Cornelis Jun 27 '22 at 07:36
  • 1
    @Cornelis That is for crewed flights. I was talking just in general. – The Rocket fan Jun 27 '22 at 08:18
  • What difference does it make whether the flight is crewed or not when discussing a gravity assist? – Organic Marble Jun 27 '22 at 13:35
  • @OrganicMarble gravity assist trajectories tend to take a long time, and a Venus gravity assist involves getting about twice the solar radiation that would be experienced near Earth for part of the trip. – Christopher James Huff Jun 27 '22 at 13:43
  • @OrganicMarble there are some downsides if it is crewed. The first major thing is solar radiation. The closer you go to the Sun the more solar radiation there is meaning that you would need a thicker wall to block it. The second thing is even though it is more fuel efficient to do the flyby, the total amount of time increases. Longer flights are not better for crewed flights. – The Rocket fan Jun 27 '22 at 13:44
  • So, it depends on what you mean by "practical". – Organic Marble Jun 27 '22 at 14:19
  • @OrganicMarble I mean since you use less fuel to do a flyby, is it worth doing it or is the extra time not worth it. – The Rocket fan Jun 27 '22 at 14:21
  • 1
    Worth it to who? Depends on the requirements, which is what I was getting at. – Organic Marble Jun 27 '22 at 14:21
  • @OrganicMarble the space agencies like NASA to send a probe via Venus to Mars. – The Rocket fan Jun 27 '22 at 14:23
  • Like if in the next few years NASA sends another Rover like Perseverance would it be worth the wait to do a flyby of Venus. – The Rocket fan Jun 27 '22 at 14:25
  • 1
    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. – Organic Marble Jun 27 '22 at 14:31
  • @OrganicMarble What information is missing – The Rocket fan Jun 27 '22 at 14:31
  • I clearly stated that I meant a probe and not a crewed mission – The Rocket fan Jun 27 '22 at 14:32
  • 2
    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". – Organic Marble Jun 27 '22 at 14:33
  • If you do not like the term practical in this use, then go ahead and edit the question. – The Rocket fan Jun 27 '22 at 14:35
  • 1
    The question whether it is practical or not is reasonable enough. The answer does not have to be yes or no. It can be a discussion of the conditions that affect the practicality. – WaterMolecule Jun 27 '22 at 18:59
  • @WaterMolecule sure. Just not a "yes" or "no" as written. – Organic Marble Jun 27 '22 at 20:13
  • "Closer" does not mean "Costs less fuel." For a spacecraft starting from Earth ,the Surface of the Sun is five times closer than the orbit of Jupiter. Reaching the orbit of Jupiter (or even escaping the Solar system entirely) costs less delta-V than impacting the surface of the Sun. – notovny Jun 28 '22 at 13:07
  • @notovny Yes it is true that closer does not always mean less fuel, but in this case it does take less fuel to get to Venus. – The Rocket fan Jun 28 '22 at 13:15

2 Answers2

6

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.

BrendanLuke15
  • 9,755
  • 2
  • 26
  • 80
1

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.

Fred
  • 13,060
  • 4
  • 41
  • 78
Magermigiegim7
  • 121
  • 6