Delta-V to get to Moho

[Zosma Procyon]

Is a Delta-V of 14400 m/s enough to get to Moho? I'm asking because I just struck out with 10,600 m/s earlier. I don't like cheating with infinite fuel, but I'm starting to think that is the only way to get to that inconvenient little rock.

I launch from Kerbin's surface direct to Kerbol orbit.

Edited January 8, 2016 by Zosma Procyon

[maceemiller]

Spoiler

Spoiler

https://www.google.co.uk/search?q=ksp+dv+map&oq=ksp+dv&aqs=chrome.1.69i57j0l3.4151j0j4&sourceid=chrome-mobile&ie=UTF-8#imgrc=RqCzp82y4M3ZeM%3A

 

Not sure why ive put link in 2 spoilers but I have just woken up lol.,

Edited January 7, 2016 by maceemiller
Error

[Rdivine]

15 minutes ago, Zosma Procyon said:

Is a Delta-V of 14400 m/s enough to get to Moho? I'm asking because I just struck out with 10,600 m/s earlier. I don't like cheating with infinite fuel, but I'm starting to think that is the only way to get to that inconvenient little rock.

I've been to moho multiple times. The first few tries, i did a direct hohmann transfer from Kerbin to Moho. The required delta-v is somewhere between 14000 to 18000m/s. However, you can lower that to around 5000m/s of delta-v using a gravity assist from Eve that sets you in a lower orbit around the sun.

[Hannu2]

Is that DV at orbit? It takes about 5000 m/s from 300 km Kerbin orbit to 100 km Moho orbit. With 14400 m/s you get there and back and have very good margins.

Moho trajectories are very sensitive to errors. Error of couple of m/s at Kerbin's SOI can lead to 1000 m/s larger orbit insertion burn. Therefore you need a proper porkchop plotter. Alexmoon's is good. You see that differences between windows are large. But for example at Y01 D269 there is quite good one. If you start from 300 km orbit you need 1441 m/s to ejection and 3540 m/s to insertion at 100 km orbit. At this time inclination is near zero so you can leave from equatorial orbit. Otherwise you can save up to couple of hundreds of m/s by using parking orbit with correct inclination and LAN. You need also some precision node mod. Stock maneuver node is simply inadequate to accurate trajectory planning.

You can begin from values porkchop plotter gives. Typically they are not perfect and you have to make small adjustments. With Moho you have to adjust 0.1 m/s and 0.1 s resolution. Of course it is impossible to make burns with such accuracy but it is good point to start. When you get an encounter be sure that Sun orbit's periapsis and apoapsis are correct. If they are not, you may need 1000 m/s more to brake on orbit (if you really have 14 km/s it is not necessary but your next craft is larger and does not have such massive overengineering).

Then execute the burn. It is better to have at least 3 m/s^2 acceleration and altitude at least 300 km to minimize errors. Check trajectory immediately after leaving Kerbin's SOI. Make correction to get right orbit. It should take less that 100 m/s. Then you may need midcourse correction at about halfway. It may be 100-200 m/s. Next correction as about 7 Kerbin days before encounter. Then you can adjust periapsis. It should not take many m/s. Next correction is about 2 days before encounter. You can finalize periapsis and make sure that you are on course. Sometimes there are strange errors on Moho trajectories. I do not know if they are fixed or not in current version.

When you enter into Moho's SOI check periapsis, save game and calculate approximated time to braking. Formulas of basic mechanics work but if you are not careful you need sometimes quickload. In my opinion it is best to burn to retrograde and time burn so that it ends soon after periapsis. Target about 100 km because periapsis falls during long retrograde burn. Stop the burn when apoapsis is well in the SOI. Wait until you are at AP and adjust PE and possible inclination. Circularize at PE and you are ready to begin exploration or landing preparations.

[Mitchz95]

The way I usually do it is to wait until Kerbin is at Moho's Ascending Node, then doing both the departure burn and plane change simultaneously. Then just do a retrograde burn at solar periapsis (or timewarp a bit) until you have an encounter.

[tomf]

According to this excelent planner you can get from Kerbin to Moho orbit for 5000m/s

https://alexmoon.github.io/ksp/#/Kerbin/100/Moho/50/false/optimal/false/1/1

Getting back will cost 5360 or as little as 2900 if you are able to aeorbrake returning to Kerbin

https://alexmoon.github.io/ksp/#/Moho/50/Kerbin/100/true/optimal/false/1/405

[Hannu2]

1 hour ago, tomf said:

According to this excelent planner you can get from Kerbin to Moho orbit for 5000m/s

https://alexmoon.github.io/ksp/#/Kerbin/100/Moho/50/false/optimal/false/1/1

Getting back will cost 5360 or as little as 2900 if you are able to aeorbrake returning to Kerbin

https://alexmoon.github.io/ksp/#/Moho/50/Kerbin/100/true/optimal/false/1/405

My best trajectory has been about 200 m/s over predicted. It took much fine adjusting and even more luck. It is good idea to pack prediction+500 m/s or even 1000 m/s.

Re-entry from Moho is very challenging. In your case braking velocity is about 2500 m/s. It gives 3900 m/s at top of the atmosphere with Kerbin's escape velocity. It is better to make sure that return capsule is able to do it.

[PnDB]

 

This thread from 2014 is from a challenge for an earlier version of KSP, but it shows what one can do with enough patience and many gravity assists.  Back then, metaphor launched from Kerbin, transferred to Moho, and landed using a mere 7217 m/s dV.  This challenge might be worth revisiting under KSP 1.0.5.

 

 

Edited January 7, 2016 by PnDB
Fat-fingered the dV value. Corrected from 7215 to 7217.

[Aethon]

Forget transfer windows when it comes to Moho.

http://forum.kerbalspaceprogram.com/index.php?/topic/55965-oh-bugger-injection-burn-at-moho/#post835667 

Scroll down to maccollos' post.  I just used his method for 6100 m/sec to Moho orbit.  To save typing I'll quote myself from another thread.

Yep the link above is the way to go and I agree this (and the link above) are too important to not necro.

http://steamcommunity.com/sharedfiles/filedetails/?id=313807386

I landed on Moho last night using macollos' method and it's slicker than snot on a broom handle. Basically you leave LKO on Mohos' AN/DN.

The first time this occurs ( IIRC the AN ) is ( Earth ) Year 1 Day 21, on or about Hour 17. Set Moho as your target and drag a dummy Kerbin escape node out to see where the AN/DN is. I combined my Kerbin escape burn with my inclination burn at a total cost of 2300 dv. At my solar periapse ( which was also Mohos' solar periapse ) I burned 1800ms retro ( as Kashua suggests. See link ) to make sure I encountered Moho on my next orbit, which lowered my solar apoapse and slowed the eventual Moho encounter down dramatically. My capture burn at Moho was around 1000ms.

Didn't know this thread was going to pop up or I would have documented better.

Use it! Props to macollo.

http://forum.kerbalspaceprogram.com/index.php?/topic/24615-delta-v-to-reach-moho-orbit/

[MalfunctionM1Ke]

Delta-V requirements are a bit tricky when it Comes to Moho, Dres and Eeloo as they are an very funky Orbits.
 

[Guest]

On 1/7/2016 at 10:36 PM, Rdivine said:

I've been to moho multiple times. The first few tries, i did a direct hohmann transfer from Kerbin to Moho. The required delta-v is somewhere between 14000 to 18000m/s. However, you can lower that to around 5000m/s of delta-v using a gravity assist from Eve that sets you in a lower orbit around the sun.

No, you can direct Hohmann transfer with braking burn for between 4.5 ~ 6km/s during most windows.  The best windows I've seen have been as little as 4.2km/s, IIRC.  Braking burns at Moho are, almost as a rule, murderous.  The AN/DN method to get to Moho is probably the best but I've never used it myself; I just pack enough delta-V to do the job.  My Moho transfer vehicles were always designed with at least 5.5km/s to include a good safety margin and I generally waited until I had a favorable window requiring less than 5km/s.  A transfer vehicle with a total of 11km/s (remember to factor in ditching any equipment you don't need to bring back) will get you there and back with a good safety margin (or orbital adjustments when you return).

Edited January 8, 2016 by regex