Challenge Time Of Flight - Brighton Beach to Olympus base.

[dgatsoulis]

Yes, it's yet another Moon to Mars challenge.
In this one though, you'll have to get a little bit out of the Hohmann-type transfer "comfort zone" and setup and fly a mission that minimizes the Time Of Flight (TOF) for the journey, using all the ΔV at your disposal.

A typical Earth-Mars journey takes about 7-8 months and uses roughly 3.6km/s of ΔV for the TMI burn (from LEO). How much time can you save, if you use the Moon as your starting point?

I've setup a DeltaGlider, landed on Pad #2 at BB, with 3600 m/s of ΔV in her tanks.(60 kg of RCS fuel included). Your goal is to land at Olympus base on Mars with minimum TOF.

You are free to use the scenario editor and advance the date to any launch window you want, but you must land on Mars BEFORE the 1st of January 2020.
The TOF counter will start the moment you ignite your main/hover engines and stop as soon as you have landed safely, within 50 km of Olympus base.

The scenario comes with a Lua script that checks if the challenge goal has been achieved and returns you a "score" with your Time Of Flight.
Unzip the attached file in your Orbiter directory and run the "BB_tlympus-TOF challenge" scenario.

You must have limited fuel checked and autorefuel on Lpad unchecked in the parameters tab.

You will get a "Mission failure" message if:
• You add fuel with the scenario editor.
• The date is later than 1/1/2020
• You hit the surface of a planet/moon with a high vertical speed. (more than 10 m/s)
• You land more than 50 km away from Olympus base.

HELP/HINTS:
Surrogate ships to help in mission planning are acceptable.

A deadstick rollout landing on Mars is acceptable (and recommended), as long as you land with a low vertical speed.

Keep in mind that this challenge is not about just making the journey. It is about making it at the shortest TOF possible.

This link from flytandem is very useful for making a plan with a surrogate ship in TransX

This post from BrianJ is for making a Moon to Mars TransX plan without the help of a surrogate ship.

If we assume ~100-150 m/s of ΔV for corrections and plane changes, the lower limit for the TOF of this journey should be ~120 days.

Have fun, happy orbiting

 

[Gr_Chris_pilot]

O my god... another challenge.. Let's get to work people

 

[boogabooga]

why am I spawning with a full tank? Yes, limited fuel is on.

 

[blixel]

why am I spawning with a full tank? Yes, limited fuel is on.

Do you have "Auto-refuel on pad" enabled?

 

[boogabooga]

Ohhh, so that's what that does...:blush:

 

[dgatsoulis]

After investigating the launch windows from now to 2020, I found a nice combination of Prograde, Pl. Change and Outward velocity, which allows a travel time of ~110 days, within the ΔV budget, provided they are used with the correct Eject date.
Add to that the ~5 days it takes to drop to Earth from the Moon and the total flight time was just under 115 days.

I still had ~100 m/s ΔV when I landed, but it was all RCS. If used properly those extra m/s can make a difference. Perhaps a 110 day flight is possible? :hmm:

 

[boogabooga]

I haven't tried this yet, be are we convinced that dropping back to earth and then reboosting is the way to go? Are we sure that the advantages of making the transfer close to earth are worth the cost of lowering perigee in the first place? I'd like to try to take a tangential rout from the moon and see what I get.

 

[dgatsoulis]

I haven't tried this yet, be are we convinced that dropping back to earth and then reboosting is the way to go? Are we sure that the advantages of making the transfer close to earth are worth the cost of lowering perigee in the first place? I'd like to try to take a tangential rout from the moon and see what I get.

After doing the math, I am convinced that this is the way to go, if you want to minimize the TOF. But that does not mean that I am certain. That's why I've posted this as a challenge.

In all the windows to Mars from today to 2019, the best I could come up with was a 110 day transfer trajectory, that was within the 3.6 km/s ΔV budget. (The first one I found was a 134 day transfer, but after checking the next window I saw that I could save almost 25 days).

I made the flight I posted my result. Feel free to investigate whatever method you think will be best.

 

[Tommy]

I haven't tried this yet, be are we convinced that dropping back to earth and then reboosting is the way to go? Are we sure that the advantages of making the transfer close to earth are worth the cost of lowering perigee in the first place? I'd like to try to take a tangential rout from the moon and see what I get.

It isn't just the Oberth effect that makes this the way to go - it's the higher potential energy. It takes about 1km/s to escape from the Moon's gravity. If we try to go straight from the Moon, we still need, what, around 2500 m/s to complete the journey on a Hohman transfer? That doesn't leave much dV available to "shorten" the trip.

Yet if we make a swing through LEO, thanks about 3000 m/s of gravitational acceleration that 1000 m/s burn will almost provide ALL the energy we need to get to Mars on a Hohman trajectory - leaving over 2000 m/s to speed things up.

 

[flytandem]

Landed with TOF = 114.91 days. A few meters from the pad.
fun task.:hello:

 

[dgatsoulis]

Nice going flytandem! :thumbup:
How much ΔV did you have left, when you hit the Martian atmosphere?
In my flight I had ~100 m/s of RCS. I think that if I manage to use some of that fuel at the TMI burn, I could bring the TOF to even less than 110 days.

-----------------------------------EDIT--------------------------------------------

I tweaked the plan of the first flight, pushing the required ΔV to the limit of the budget.
I used as much of the RCS fuel I could; before, during and after the TMI burn. The result was a successful 108.81 days flight. I landed with 2.74 kg of RCS fuel still in the tank, having used 3590.04 m/s out of the 3.6 km/s budget.
A few screenshots:

10 minutes before Periareion:

Just before wheels-stop. Checkout fuel and ΔV left:

The "Challenge completed successfully" msg:

 

[astrosammy]

Too hard for me. I see that flytandem has a Moon-Mars video tutorial, maybe I'll try again after watching.
Honestly, anyone who can do this should set his experience to "Expert" (And I should set it down to "Advanced" ).

We certainly need more of this lua challenges. I'll create some soon...

 

[downloaderfan]

Started off from brighton beach,did the normal ascent and ejection burn from moon without problems,then came the thinking part.
Had to burn off RCS before doing the main ejection burn,this was the result after it

Then things got desperate while planning the main ejection burn:

Then after reaching Mars......I was like :woohoo:

Aerobraking began and was captured by mars

Then....wasn't looking at the keyboard,wanted to press R but pressed T,AoA hold in aerobrake MFD was on and the ship went out of control and lost all RCS.Then i was like :beathead:
Then this was the final end:

:dry:

I'm still quite happy i was able to get this far with a decent TOF

Thanks to dgatsoulis for checking and correcting out my math.

 

[dgatsoulis]

I'm still quite happy i was able to get this far with a decent TOF

:thumbup: I'd say more than decent!. Excellent job downloaderfan.