Need help plotting course.

[Falkenherz]

Here is my problem. Looking at various deltaV-maps I cannot find the answer myself, so maybe some pro out there can help me:

1. My mothership is currently landed on Minmus surface and has 700m/s deltaV left. I want to launch, get into solar orbit and then get back to Kerbin. Do I have enough deltaV for doing this? If not, how much would I need?

2. I have a small dinghy attached with a separate deltaV of 3500m/s. Once in solar orbit, I want to undock it and go on a quick solar suborbit with it and then re-dock. (Yes, it is one of those tourist contracts). How do I do this most efficiently; do I have to enter solar orbit by burning retrograde (to Kerbin´s solar orbit) out of Minmus orbit instead of a prograde burn before I undock the dinghy? What about an ejection from polar orbit?

Edited June 22, 2015 by Falkenherz

[Warzouz]

Farming for XP I see.

Well, this should be possible with 700m/s.

From memory (I can't check the charts here)

- Minmus off = 200m/s

- Escaping Minmus = 80m/s

- To Solar SOI = 90m/s

- Eliptic orbit with PE around 40km = 200m/s ?

Don't forget to save before though...

[Superfluous J]

700 is pretty low, but I think you can do it. Technically.

I use http://i.imgur.com/UUU8yCk.png which is wrong in atmo since 1.0 but the rest is still correct.

You need about 180+70+90+20 to escape Kerbin SOI from Minmus' surface, or roughly 360 m/s. To get back to Kerbin SOI you can either do a tiny burn and wait about half a year to get back, or burn up a few hundred m/s to get back quicker. That's the hardest part of this, from a dV standpoint.

If you opt to wait half a year and use maneuver nodes (and some patience and trial/error with them) you can from outside Kerbin's SOI return to Kerbin for a few m/s. Maybe 10. If you opt to do it right away, you'll use (as I said) a few hundred just to get back to Kerbin's SOI.

One trick if you opt for the faster journey: You don't need to get back to Kerbin. You just need to reach Mun's SOI. If you angle it correctly, you can come in, swing by Mun, and exit Mun's SOI backwards which should drop you nicely onto Kerbin.

And to answer the unasked question you assumed, the charts really aren't designed to answer most of this question

Edited June 22, 2015 by 5thHorseman
Didn't see you were on the surface.

[capi3101]

<snip />I use http://i.imgur.com/UUU8yCk.png which is wrong in atmo since 1.0 but the rest is still correct. <snip />

Updated image for 1.0.x at http://i.imgur.com/9vVZMxq.png, BTW.

You'd need 360 to launch from Minmus and escape Kerbin, so that part you could do. Whether the 3500 in the dingy could do the trick or not, though, is questionable; the way I'm reading it is a flat out no, but others might have different opinions. Maybe with a bi-elliptic transfer maneuver.

Edited June 22, 2015 by capi3101

[Snark]

Concur with the earlier posters' response that 700 m/s is easily enough to leave Kerbin SoI from Minmus surface and then return. You don't have to wait half a year, and you don't need hundreds of m/s of dV to return. All you need to do is to manage your Minmus ejection so that you're in an elliptic orbit around Kerbin whose apoapsis just barely leaves the SoI. That will take a few weeks of calendar time, but it means you'll leave Kerbin's SoI with a very low velocity relative to Kerbin, which means that you can then use a fairly low dV burn to head home again.

As for your dinghy question:

What exactly is the dinghy supposed to do? You didn't say exactly what your tourist contract is for. If it's just "orbit the sun", you don't need the dinghy at all-- simply peeking outside Kerbin's SoI is all you need, because you're orbiting the Sun the moment you do that. You're already doing that with your main mothership, so no extra dinghy shenanigans required.

On the other hand, if you've got one of those "suborbital trajectory on the Sun" contracts, I'd say that 3500 m/s would be nowhere near enough. Maybe you could finesse it with a bielliptic transfer, if you're willing for the trip to take many years. Anything that drops your periapsis down to the sun is going to have huge dV requirements, that's why Moho takes so much dV to visit.

[Falkenherz]

Thanks, guys! This helped me a lot to dare the step out of the Kerbin door! Just to clarify, this is a mega voyage with 10 tourists and 9 Kerbonauts; the tourists finance the flight, the Kerbonauts are indeed just along for the experience (and some science)... Details about my ventures are in my blog.

This is the deltaV data I was able to achieve:

Just be be on the safe side, I had a fuel ship close by and rerouted it to my mothership.

Launch from Minmus to 16kmx16km orbit in for a rendez-vous: from 719m/s down to 509m/s.

After a refuel of 1080 fuel (three 360 tanks), I had 1234m/s ready.

Being able to leave Kerbin SOI after 8d3h downed my dV from 1234m/s to 1109m/s.

I also remembered that I had a satelite still in solar orbit; testing the sun suborbital said I needed a dV of 7596m/s! And there I thought 3500m/s would be perfectly enough... no idea how to give that one remaining tourist his suicidal experience! Launching anew from Kerbal, this means I would need a dV of about 16.000m/s (including the required return)! How is that even achievable??? I don´t have LV-N´s yet, can they achieve this?

[capi3101]

It's possible, yes, but the fuel fraction is going to be significant - for 16,000 m/s and an 800 Isp, you're talking about having roughly 87% the mass of your craft as fuel.

I might suggest ions in this case, but if you haven't got nukes it's a fair bet you haven't got ions either. Damn shame you can't strap a tourist into a seat...

[Falkenherz]

Wiki says that a bi-eliptical transfer could get dV requirements down to ~4,000m/s.

Kerbol suborbit starts at 1,000km? Does a fly-by below 1,000km count as a sub-orbital flight?

Tough nut to crack; my science is still hanging around the 160-point nodes, with a few 300´s unlocked. Scratch off my dinghy; will need a new launch with a highly specialized craft in order to pull this off.

[SAI Peregrinus]

http://forum.kerbalspaceprogram.com/threads/36476-WIN-MAC-KSP-Trajectory-Optimization-Tool-v1-3-3-Update-for-KSP-1-0!

That tool is complicated, but it can find even quite complex transfers. And the plugin can make the maneuver nodes.