How to Rendezvous using IVA view only!

[alterbaron]

Hi all,

Here I'll show you how to rendezvous with another vessel using ONLY the IVA view (the in-cockpit view). The map view is completely unnecessary!

This practice ship uses the MK1 cockpit to provide a nice, wide window, making life easier if controlling in IVA.

IVA Rendezvous Trainer Ship

Initial setup for demonstration.

Two practice ships were flown up separately. One was placed into a 200km x 200km orbit, and the other into a 250km x 250km orbit. (Ships were flown up in IVA mode as well, but that's a walk in the park compared to rendezvous.)

Note: The altimeter in IVA can't measure 100,000km increments, so figuring out your actual orbit altitude is an interesting exercise!

Anyways, let's rendezvous the lower ship with the higher one.

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Instructions:

Measuring Target Crossing Time

Line up the navball so that the cross-hairs lie on the center of the blue hemisphere.

Wait for the target to cross the center of the screen, while keeping the navball in position. When this happens, write down the time (displayed a the top left corner of the screen.) Call this time t0.

I measured t0 = 1:01:09:15

A Bunch of Calculations

Basically, we need to figure out at what time to burn to intercept our target. We also need to figure out the velocity we need to burn to. These formulas give us everything we need:

Some notes:

r1 is the orbital height of the lower ship, measured from the planet's center. This means we need to add the planet radius (600,000m for Kerbin).

r2 is the orbital height of the higher ship, measured from the center of the planet again.

t0 is our initial crossing time as measured in the last image.

The funny "u" looking symbol is called "mu", and represents the gravitational parameter of the planet. For Kerbin, this is 3.5316 x 10^12 m^3/s^2.

Calculations done!

Using those formulas, I get:

tR0 = 27522 seconds (This is how long until our ship and the target ship are lined up again.)

tH = 1253 seconds

deltaTheta = 0.1368

deltaTBurn = 26923 seconds

We need to add this 26923 seconds to our time t0 to figure out when to burn. Converting to hours, minutes and seconds and adding, I get:

TBurn = 1:08:37:58

This is the time (top left of screen) at which we need to burn to intercept our target.

We'll burn prograde until our velocity is equal to Vtransfer = 2133m/s.

About to burn . . .

Burn complete!

We're now within 20km of the target!

At this point, you can take the controls and fine-tune the intercept.

And that's it!

Best of luck if you want to try this out! Let me know if you have any questions.

[JiWint]

Is it wrong that I docked without maths and rcs using IVA?

[alterbaron]

Not wrong, but pretty impressive if you can pull that off.

For two orbits that are already really close, it's quite possible to do the whole thing in IVA without any calculations (but it's a little more fuel intensive.)

The math really helps, though, if your target vessel is more than 50km away at the point of closest approach. At these distances, you'll waste fuel like a madman if you just burn towards your target. Instead, a Hohmann transfer (at the heart of this method) is the way to go.