Question Runway landing

[worir1]

I have succeeded in traveling to every planet in orbiter in the XR2 i have done landing and re entry with precision but the one thing i have never been able to do is dock. Is there a way to dock to a ship if your already in a random orbit?

 

[Urwumpe]

I have succeeded in traveling to every planet in orbiter in the XR2 i have done landing and re entry with precision but the one thing i have never been able to do is dock. Is there a way to dock to a ship if your already in a random orbit?

Sure. But you should first learn a new term: Rendezvous.

Docking is just the easy part of it, what you want to do is long distance relative navigation, called Rendezvous.

For that, you first of all have to be in the same plane - so align plane is a good start. For aligning plane, remember that the fuel consumption for that maneuver increases with your velocity: the faster you are, the more expensive it is. Thus it is recommend to do plane changes near apogee and correct the plane, when you are far away from the planet. For example by Not braking into a circular orbit when you arrive at a planet, but just entering into an ellipse.

 

[worir1]

Sure. But you should first learn a new term: Rendezvous.

Docking is just the easy part of it, what you want to do is long distance relative navigation, called Rendezvous.

For that, you first of all have to be in the same plane - so align plane is a good start. For aligning plane, remember that the fuel consumption for that maneuver increases with your velocity: the faster you are, the more expensive it is. Thus it is recommend to do plane changes near apogee and correct the plane, when you are far away from the planet. For example by Not braking into a circular orbit when you arrive at a planet, but just entering into an ellipse.

Rendezvous is what i ment. Thank you.
Lets throw fuel efficiency out of the window. I know how to align planes with the vessel, say for example the ISS. However when i am aligned i can never catch up or slow down with the ISS. I know to slow down if the vessel is behind you you must increase your orbit high above the target and to speed up you should make your orbit smaller than the target. My problem is i can't figure out when to do the retro/prograde burns to just my orbit to intersect the target. I have often used transfer MFD to do this burn. It works sort of... I always end up with a very high relative velocity and can never seem to slow down enough to dock. So on that sense i have achieved rendezvous but failed docking. Can any one recommend a MFD i can use to calculate the burn?

 

[Urwumpe]

The standard solution is the Sync Orbit MFD, which you can use for that task. You select first just a fixed "goal line" to approach the target, doing small burns for reducing the number of orbits until a minimum time is reached. when you are close, you intercept the target by burning into you have an intersection, and then you use linear RCS and thrust to get the next pass time difference to zero.

It is not really fast, but pretty fuel effective in small steps.

Better solution is combining some experience with IMFD, which can do much better intercepts.

For the final 30 km, I recommend Rendezvous MFD... but it is a bit hard to use if you have not yet learned relative navigation.

For practising, you should just undock from the ISS in a scenario and play around: Forward means up, up means backwards, backwards means down, down means forward. Find out, what that means.

 

[worir1]

Forgetting fuel efficiency what is the fastest and easiest way?

 

[garyw]

Scenario editor.

assuming you want to do this yourself, do you know how to align planes?

Once you are plane aligned it's a matter of catching up to the target or letting it catch up to you then closing for docking.

 

[Cras]

Forgetting fuel efficiency what is the fastest and easiest way?

IMFD. Just set it up for a path that wont take you through the center of the Earth, burn, keep an eye that you are still on course, and then use IMFD's velocity match program when you are close. If you dont care about fuel efficiency, it is real easy to set up IMFD for a rendezvous that leaves you with quite a bit of relative velocity, that will take quite a bit of dV to null out. But if you got the XR-2, it can handle that sort of thing with ease.

 

[ADSWNJ]

Forgetting fuel efficiency what is the fastest and easiest way?

http://www.amcsorley.dsl.pipex.com/play_in_space.htm

Forget fastest & easiest, this is the best way. Read the Dancing in the Dark chapter, so you understand the fundamentals. Then by all means use tools like IMFD to skip steps, but with an understanding of what you are doing and why.

I think reeling in the ISS for a docking, or docking to something tricky like that Luna space station at the moon is really satisfying, especially in an XR-5 or Shuttle where you are actually docking through a top port on your ship.

If you get really into it, you can align your ship to have the exact same eccentricity and AgP of the target, so you are essentially riding the same egg-shape orbit as the target, and you can come in with less than 20 m/s of delta-V. Docking in an XR or a DG allows you to abuse it a bit because the engines are really powerful, but when you try in the Shuttle, or even better in a Zarya or equivalent with tine engines, you need to really get precise with your approach.

My new RV Orientation will guide you in from say 10 km out to fully docked, tracking down to tenths of degrees of angle and centimeters of translation offset. It's a new experience!

 

[downloaderfan]

Original credit for Glideslope should all go to Chris Jeppesen (kwan3217). I was working from an awesome base in Glideslope 1, but I added quite a few features in Glideslope 2.x that help with controlling a landing like this.

On the HAC - I have never flown it with a joystick, so I can say for sure it's flyable off the keyboard. I made the size and orientation of the HAC adjustable to allow you to do adjustment according to speed, energy and angle on the final glideslope. It's an interesting balance actually. Too fast and when you hit the HAC you will not be able to turn in (i.e. you skid out of the turn despite being banked at 60 degrees and pulling up hard). To handle this - switch the HAC geometry to the far side, and adjust the HAC radius big enough to roll round the turn without having to pull up too hard.

If you are coming in too slow, and you will need to switch the geometry to straight-in and eke it out to the runway. If you get it just right, you can glide around the HC without bleeding off too much energy, and arrive at the top of outer glideslope at a 20 degree perfect angle.

If you are coming in too high, then you will also have problems turning, as the air is less thick, so the ship doesn't bite enough.

The only interesting one is low and fast, where you have turning authority, so you can do a climb, loop and turn to transfer velocity into potential energy.

Over to the final approach, you have two sighting points - the PAPI and the VASI. If you are used to any flight sim flying (or real Cessnas for that matter), this is a weird concept, but the goal is to come down the outer glideslope at the 20 degree angle, to about 100-200m alt, then pull up smoothly onto the inner glideslope at 1.5 degrees, and kiss the runway really gently (holding the velocity vector just on the target touchdown point).

Find an approach range you are comfortable with (e.g. some of the Glideslope saved scenarios), and run them 20 or 30 times, adjusting by small amounts each time to develop a feel for spotting and correcting deviations from a perfect trajectory. It gets better with practice, I promise!

Ok,after quite a few tries of HAC,i think its possible to do HACs with a keyboard.However,i get easily misaligned with the line of HAC circle in glideslope as there is no maintaining of pitch and bank without a joystick.Off course the XR2 has attitude hold controls but i just cant set it up to get the perfect precision in such cases.Its too much of work with just the keyboard.Or maybe it needs even more,a lot more practice to do it with ease.

My mistake,thanks to kwan3217 for making glideslope MFD,which inturn gave u the idea to make an ever better glideslope 2 MFD. :thumbup:

 

[ADSWNJ]

It was a real labor of love to try to figure out the original Glideslope, as part of the source was missing and the comments were quite skimpy. So I had to patch it up even to get it to compile.

On the HAC turn - I agree it's tough to fly right on the curve. Don't sweat it too much, and feel free to adjust the HAC radius even mid-turn. I'd love to have that attitude roll control down to 1 degree fine resolution, versus 5 degrees min, especially for that kind of profile!

Immediately prior to going into the HAC, bring the spaceship to straight and level, so that the wings get the best chance to 'bite' into the turn. It's an interesting combination of how much you roll and how much you pull up into the turn. I try to pull up as little as I can, and if I needed to do it, I spend the HAC loop dropping my nose back (which makes the track slide out of the turn), and adjusting back in more roll (which gets increasingly better as you descend). Ideally, you want to keep the profile and control surfaces as clean as possible (i.e. get back to a few degrees of pitch-up and 30-40 degrees of roll), so you can come around the turn without losing too much energy.

Then roll out into the outer glideslope with 20 degrees, nose down, airbrakes on, and you are a couple of maneuvers from home.

 

[worir1]

Thanks guys ! After 4 attempts i docked. I appreciate the help. ( sorry for going off thread topic)

 

[ADSWNJ]

Thanks guys ! After 4 attempts i docked. I appreciate the help. ( sorry for going off thread topic)

Congrats. Feels good, doesn't it?!

 

[worir1]

It does