maneuver nodes and approach velocity

[Lechu]

Is there a way to see what is going to be the craft's velocity, when said craft will be approaching a planet, after setting up series of nodes?

Without wrapping all the way there, and performing all the planed maneuvers, that is.

[VoidSquid]

Yes, using this mod:
 

 

[bewing]

You can calculate it by hand fairly quickly using the vis viva equation.

[Lechu]

3 hours ago, VoidSquid said:

Yes, using this mod

Thanks.

 

I am trying to set up the return to Kerbin after fly-by Eve. I am fairly new to the interplanetary travel.

Will I be able to aerobrake at about 5500m/s? This is my speed at  the Kerbin  periapsis.

I would need almost  2200m/s of deltaV to stay on Kerbin orbit. I expect to have about 300m/s. Is it even possible to bleed that many deltaV without exploding?

Or should I give up and look after another solution, like refueling at the solar orbit?

[VoidSquid]

I wouldn't go directly into Kerbin's atmo at that speed, I usually first go into an orbit of say 250x250 km, only then go for landing with the usual Pe of about 30 km.

You make it maybe into a very elliptic Kerbin orbit and send kind of a rescue / refuel rocket?

Or make an elliptic orbit with the Pe just below 70km and do multiple aero breaking orbits.

Edited November 2, 2020 by VoidSquid

[Lechu]

I don't even want this craft to land. Not all of it.  It is not build that way. All I hope for is very elliptic Kerbin orbit, as re-fuelinging would be orders of magnitude easier then doing it on solar orbit.  Unfortunately, craft  does not have a heat shield.

Do you think I'll be able to dip into atmo deep enough to shed about 2000m/s dv, in one pass, without exploding?

Or should I re-design the entire flight plan?

 

[VoidSquid]

2000 m/s in one pass, no. Remember, LKO means 2300 m/s, that's not much more.

If you can't reach even an elliptical Kerbin orbit, what about sending a rescue mission to Eve instead?

[Lechu]

15 minutes ago, VoidSquid said:

a rescue mission to Eve instead

I am not going to stop at Eve, the craft will just zip through there. I have contract to do a flyby.

The mission is going to show up back  around Kerbil in about one and half a year, though.

I am thinking of some unmanned probe meeting it on solar orbit,  to refuel and maybe provide a heatshield, to be docked with crew cabin.

But it is going to be tricky to set up.

[VoidSquid]

Going into Eve orbit first starts with a fly-by trajectory, i.e. that fly-by check should be fine when you're going into Eve orbit.

[Lechu]

I see what you mean, but craft's velocity while passing Eve will be even bigger, 59000m/s, while having about 600 m/s dv to work with.

If I cannot aerobrake at Kerbin, Eve is even more out of the question.  It is my fault, when staring this mission I just wanted Eve encounter,  I thought that I will somehow figure up the means of safe return afterwards.

Do you think that having the biggest heatshield would make a difference?  Would I, with it,  be able to shed 2000m/s dv, in single pass?

[VoidSquid]

5 minutes ago, Lechu said:

craft's velocity while passing Eve will be even bigger, 59000m/s

That's an awful high number, you're sure it's correct?

I remember Moho, which is well known to require a crazy dv number to break speed, I needed to break some 3300 to reach a reasonable Moho orbit. But Eve, almost 6000 m/s?

The problem with such such aero breaking maneuvers: set the Pe too high, and it won't even make Orbit but keep the hyperbolic trajectory. Set the Pe too low, and you'll land or burn up. Requires a lot of try and error.

10 minutes ago, Lechu said:

having about 600 m/s dv to work with.

Yeah, that's way not enough, no doubt. Hmm... I'd think that only leaves a rescue mission with a rendezvous orbiting the sun.

I have strong doubts that any other options are viable, unfortunately. Maybe other fellow Kerbonauts are more clever and have better ideas?

[Zhetaan]

1 hour ago, VoidSquid said:

I have strong doubts that any other options are viable, unfortunately. Maybe other fellow Kerbonauts are more clever and have better ideas?

I don't know about 'better', but if you're willing to spend some time, then multiple gravity assist passes of Kerbin can raise your periapsis and lower your closing velocity to the point that the Mun can capture you into orbit.

[Lechu]

Hi, I am still trying to figure it out.

When my Eve expedition is going to zip through Kerbin SOI it is going to look like that:

It is almost as if I have been trying to intercept an asteroid that threatens Kerbin. And I have well over a year for preparations. But I cannot figure out how to match orbit with something like that. It is hyperbolic orbit, right? How one is catching up with is, preferably before it passes Kerbin  periapsis?

[AHHans]

1 hour ago, Lechu said:

How one is catching up with is, preferably before it passes Kerbin  periapsis?

What I do when I catch asteroids that pass through Kerbin's SOI is to:

• Match the plane of the asteroid's future orbit.
• Get into an elliptical orbit that crosses the asteroid's future orbit
• Set a maneuver node on my orbit at a place outside the asteroid's future orbit, usually on the line from Kerbin -> asteroid's PE -> my orbit
• Hit "next orbit" on the maneuver node until the intersect nodes on the asteroid's track appear. (If it's too far in the future I just wait before setting up the node (KAC is your friend.)
• Set up the node so that a prograde burn will give me a nice intercept - you need to balance the "next orbit"/"previous orbit" with the amount of prograde dV.

[Lechu]

Thank you for your answer. But how do I match the inclination of  orbits? It is not showing me any AN or DN nodes.

9 hours ago, AHHans said:

Match the plane of the asteroid's future orbit.

Edited November 14, 2020 by Lechu

[AHHans]

1 hour ago, Lechu said:

Thank you for your answer. But how do I match the inclination of  orbits? It is not showing me any AN or DN nodes.

In general there should be. Did you target the asteroid, so that it shows its patched conics in the map screen? What is also possible is that the AN and DN are not on the part of the orbit that is inside Kerbin's SOI. Try fiddling around with a maneuver node.

[Lechu]

25 minutes ago, AHHans said:

In general there should be. Did you target the asteroid, so that it shows its patched conics in the map screen?

The problem may be, it is not, in fact, an asteroid. It is the future orbit of a interplanetary craft, the orbit after several planned course corrections.

It seems KSP is not showing AN, DN or intersect nodes for interception of the planned orbits.

But I found a workaround, I think. If I plan encounter from the point of view of approaching "asteroid" ship, targeting the rescue vessel, it shows relevant  nodes.

I am going to keep changing the orbit of the rescuer, and then switching to approaching craft, to check how to nodes are changing.

Unless there is more direct method?

 

Edited November 14, 2020 by Lechu

[AHHans]

19 minutes ago, Lechu said:

It is the future orbit of a interplanetary craft, the orbit after several planned course corrections.

Yea, well, I haven't done that before...

How much time is there between the last maneuver of the interplanetary craft until it enters Kerbin's SOI? Would that be enough to set up the orbit of the intercepting craft? If not then you probably have to do it the way you described.

[Lechu]

2 hours ago, AHHans said:

How much time is there between the last maneuver of the interplanetary craft until it enters Kerbin's SOI?

52 days.  It should be enough, but I want to have  a rescue ship in place ahead of time. This entire situation is an effect of of my "good enough, I'll look into details latter" slapdash planning.

[AHHans]

I rest my case.