Flight Question Vertical rocket launch; how to determine/achieve correct roll attitude?

[Pithecanthropu]

Some time ago I downloaded KB9LAD's Acme Rocketship, something of a tribute to the pointy-ended, bullet-shaped spacecraft of early science fiction, with a liberal dash of humor in the spirit of Bugs Bunny and the Road Runner.

However, here, as with all vertical launches, I have the same problem: how do I achieve the correct orientation, so that if I pitch the nose towards the horizontal, I achieve an eastward trajectory or orbit? If I imagine myself as the pilot, sitting tipped over on my back in "space capsule launch position", is there an Orbiter standard that says my head is pointing to the North, for example? The HSI isn't any help because the situation is akin to being at the South Pole and being told to "go east". How do I figure out where East is? How do I plan a roll maneuver to achieve the correct horizontal attitude, in order to tilt the rocket in the correct direction?

Is it something I can specify in the Scenario Editor before launch?

 

[TSPenguin]

I think LaunchMFD is for you.
It should give you correct direction your bottom/roof needs to be facing.

 

[Andy44]

Yeah, a whle ago I requested a "Launch Compass" MFD, which got made seperately and then Enjo got permission from the developer to incorporate it into LaunchMFD, which works great: [ame="http://www.orbithangar.com/searchid.php?ID=2802"]Launch MFD - v 1.2.8[/ame]

 

[Pithecanthropu]

I've downloaded it, but I honestly can't make head or tail of it from the doc. What do they mean by LAN? It's an acronym that just seems to be introduced on page 2 without prior explanation, and it seems to be important.

I'm trying it with the DG now, but it doesn't seem to be any more helpful there than just the Map and Orbit MFDs.

 

[tblaxland]

I've downloaded it, but I honestly can't make head or tail of it from the doc. What do they mean by LAN? It's an acronym that just seems to be introduced on page 2 without prior explanation, and it seems to be important.

Longitude of ascending node: http://en.wikipedia.org/wiki/Longitude_of_ascending_node

Yes, it is important because it will allow Launch MFD to determine at what time your target orbital plane crosses your launch site (if at all). Note that if you are putting LAN/inclination data in to Launch MFD they need to be in the ecliptic reference plane. Launch MFD also allows you to select a target object from which it derives the ecliptic LAN/Inc.

 

[Pquardzvaark]

Since there's a thread about it, I won't mind asking if there's a way to get the correct azimuth or roll attitude without an MFD.

I guess I've got some paranoia of being too dependent on those things.

 

[tblaxland]

You can do it by pitching slowly from 90° to say 85°, rolling at the same time and watching the HUD heading tape. That is how the automatic guidance in Vinka's Multistage works but it is quite a difficult thing to do manually. And don't worry too much - MFDs tend to be pretty reliable and, in the Orbiverse, the conseqences are not too harsh even if you crash your vehicle

 

[atuhalpa]

There is another way and that is to determine your correct heading and then enter it into the HEADING parameter in the scenario file. Then all you have to do is worry about your launch profile pitch. I have used this method many times for near perfect Rinc upon MECO

 

[Pquardzvaark]

Now that sounds like cheating!

Oh, I know those MFDs are fine but I've been warned about trusting those conniving computers too much...

 

[Andy44]

It is cheating...unless you're using a Soyuz rocket which has a rotating launch rad.

 

[atuhalpa]

I believe that launches in real life have the azimuth and pitch completely computer controlled, so how is dialing in azimuth cheating? You still have to control pitch for an efficient ascent.

 

[tblaxland]

I believe that launches in real life have the azimuth and pitch completely computer controlled, so how is dialing in azimuth cheating?

Just that in real life they do the roll once you are in the air, not on the ground. Don't worry about it though - the beauty of Orbiter is that it is so flexible you can do almost anything you want

 

[Pquardzvaark]

I don't know, I just don't too much to be computer controlled. The whole spam in a can thing. If it's not a complete PITA to do, might as well do it manually.

 

[Andy44]

Launch MFD doesn't fly it for you, it just gives you cues to guide you along. Fact is when you're sitting still on a vertical launcher there is no way to find your launch azimuth without some sort of compass to look at. LaunchMFD shows you that compass.