Orbiter-Forum  

Go Back   Orbiter-Forum > Orbiter Space Flight Simulator > MFD Questions & Help
Register Blogs Orbinauts List Social Groups FAQ Projects Mark Forums Read

MFD Questions & Help Post your questions here for help with the Multi-Function Displays.

Reply
 
Thread Tools
Old 07-05-2018, 01:17 AM   #1
markopolo5437
Orbinaut
Default Difference between CVEL and RVel

I'm working through Tex's excellent video tutorial on Launch and Docking, and I noticed that there are different values for the Docking MFD CVEL and the Sync Orbit MFD RVel. Obviously, I'm missing something about what the two values indicate. CVEL is closure velocity, I believe, and RVel is Relative velocity. How are these two values defined differently?

BTW, I feel obligated to commend Tex for his Orbital Tutorial Series for Beginners. They are well-executed, detailed, and explanatory of the various sim functions and the relevant mechanics. In another thread, I disparaged his video tutorials on IMFD. Those are indeed badly out of focus and almost useless, to me.

Thanks in advance.
markopolo5437 is offline   Reply With Quote
Old 07-05-2018, 02:33 AM   #2
Zatnikitelman
Addon Developer
 
Zatnikitelman's Avatar
Default

It's been a while, but I believe CVEL is the velocity relative to the docking port while RVEL is the velocity relative to the vessels. On a straight in docking, they should be identical, but if your port is rotating, I believe there is a difference. I think that's useful if you're approaching something like a rotating space station, that lets you sync RVEL, but it's been a while since I've done Orbiter so this may not be correct.
Zatnikitelman is offline   Reply With Quote
Old 07-05-2018, 06:13 AM   #3
Tommy
Orbinaut
Default

CVEL is, as you said, Closing Velocity. It only considers velocity as a function of linear distance from the docking port, and ignores any "sideways" movement not on that direct line.

If your velocity vector is exactly aligned with the port CVEL = RVEL. If your velocity vector is not aligned with the port, the law of Cosines applies, and CVEL = RVEL times the Cosine of the angle of deviation.

In practical application, CVEL could be measured by a laser using the doppler effect, much like Police Speed detection Radar works
Tommy is offline   Reply With Quote
Thanked by:
Old 07-05-2018, 09:10 PM   #4
markopolo5437
Orbinaut
Default Docking

Thanks, guys. That helps me to understand what's going on.

Docking is more difficult than I'd thought; I'm unsuccessful after 4 or 5 attempts, but I'll get it eventually. Balancing ROT and LIN thrusters takes a lot of practice.
markopolo5437 is offline   Reply With Quote
Thanked by:
Old 07-07-2018, 02:55 AM   #5
Tommy
Orbinaut
Default

I recommend learning how to dock with Gravity Gradient Torque turned off, until you get the hang of it. Installing the Absolute Killrot add-on doesn't hurt either.

The other main secret is patience. and start by getting RVEL as close to zero as you can. Then keep the RVEL under 10 m/s.
Tommy is offline   Reply With Quote
Old 07-07-2018, 03:34 PM   #6
ADSWNJ
Scientist
 
ADSWNJ's Avatar
Default

Quote:
Originally Posted by markopolo5437 View Post
 Thanks, guys. That helps me to understand what's going on.

Docking is more difficult than I'd thought; I'm unsuccessful after 4 or 5 attempts, but I'll get it eventually. Balancing ROT and LIN thrusters takes a lot of practice.
It sure is tricky. You are trying to solve for six independent degrees of freedom all at the same time. If you have *any* residual rotation on the target vessel, then the port will have a wobble on it that makes things really challenging. (Hint: F3, select the target vessel, then engage zero rotation, then F3 and back again to your vessel).

Have a look at RV Orientation on the orbithangar.com ... my MFD to give you precise manual or autopilot control of the approach and docking.
ADSWNJ is offline   Reply With Quote
Reply

  Orbiter-Forum > Orbiter Space Flight Simulator > MFD Questions & Help


Thread Tools

Posting Rules
BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
Forum Jump


All times are GMT. The time now is 01:48 AM.

Quick Links Need Help?


About Us | Rules & Guidelines | TOS Policy | Privacy Policy

Orbiter-Forum is hosted at Orbithangar.com
Powered by vBulletin® Version 3.8.6
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.
Copyright 2007 - 2017, Orbiter-Forum.com. All rights reserved.