Launching Aids

[dremits]

Hi,

I'm quite new to orbiter but I think i have grasped the basic concepts. I just was wondering what the best aid (MFD) is for launching?

I'm using the DGIV for flight and have tried launching but normally end up with a poor orbit, a massive relative inclination from ISS (which is where I want to get) and with most of my fuel gone. I want to have an MFD that will tell me the required heading and guide me on my pitch to get a fuel efficiant trajectory. I've been exploring the Luanch MFD (if someone has a better option then please let me know) but I can't really get the hang of it. I assume once entering the target (ISS) I wait for a lauch window and then follow the X to make sure I have the right heading and pitch. The problem is that the heading appears to be wrong (It's saying something in the 100s when I know that ISS heading is around 40 isn't it?). Perhaps I've just completly misunderstood the MFD? A little guidance in this area would be a big help.

Thanks.

 

[T.Neo]

It's saying something in the 100s when I know that ISS heading is around 40 isn't it?

It's both.

You can launch to around 100 but the Shuttle launches to around 40 to avoid Cuba.

 

[Bj]

In my own opinion,

[ame="http://www.orbithangar.com/searchid.php?ID=2802"]Launch MFD - v 1.2.8 [/ame]is best

 

[dremits]

Hey thanks for the replies. Ok so any reason to go for a particular heading? surely one of them is the direction in which ISS is traveling?

 

[Urwumpe]

Hey thanks for the replies. Ok so any reason to go for a particular heading? surely one of them is the direction in which ISS is traveling?

The direction depends on the launch window. The orbit of the ISS looks roughly like a sine wave on the surface of Earth, first passing from South to North and then from North to South. The launch azimuth is the sum of the rotation speed of Earth at the launch site and the velocity vector of the target.

You can launch into 42° when the ISS ground track over your site goes from South to North or you can choose ~140°

In reality, 140° is not used, because this direction would launch over land and has a strong lack of emergency landing sites as you would travel over the South Atlantic.

 

[RisingFury]

"Launching aids" sounds so wrong...


Usually I just use the Align Planes MFD right from takeoff. I wait until the orbit is as close it gets before I takeoff, then just launch into the direction that will have the change in inclination 0.

 

[RSWingman]

I would use the map MFD with ISS as your target. Wait for the two lines (however different in amplitude) to be in perfect phase, then launch 90 deg.

After establishing orbit, I would do a plane correction burn with Orbit + or - upon crossing the equator until the amplitudes match.

If there's a better way to kill both birds with one stone, I'm not there yet.

I think one is supposed to try to launch when the ISS is directly overhead for the quickest rendezvous. I'm not there yet either. I don't really like to mess with ISS because it's plane is so far off flat. Seems counterproductive for going anywhere out of Earth's orbit. Like if you wanna go to Mars, you could refuel at ISS, but then waste nearly as much fuel as it took launching into orbit, just to zero your plane. What's up with that? I might change my ISS to an equatorial orbit if I get around to it.

 

[agentgonzo]

In reality, 140° is not used, because this direction would launch over land and has a strong lack of emergency landing sites as you would travel over the South Atlantic.

Plus it goes over Cuba and the Americans and Cubans don't get along.

 

[dremits]

Thanks for all the replies. Urwumpe, in my case the actual heading is from South to North but launch MFD is directing me in the ~140 direction ie from north to south. Why does it do this?

 

[Bj]

Like if you wanna go to Mars, you could refuel at ISS, but then waste nearly as much fuel as it took launching into orbit, just to zero your plane. What's up with that? I might change my ISS to an equatorial orbit if I get around to it.

Just dock with MIR or better yet, plan ahead and launch a fuel tank with an STS on the correct orbit inclination.

[ame="http://www.orbithangar.com/searchid.php?ID=2650"]simple tank payload 2.5[/ame]

---------- Post added at 11:56 AM ---------- Previous post was at 11:54 AM ----------

Thanks for all the replies. Urwumpe, in my case the actual heading is from South to North but launch MFD is directing me in the ~140 direction ie from north to south. Why does it do this?

Perhaps the ISS is on its way south... watch map MFD and wait until the ISS is on its way north, and somewhat close to Cape Canaveral.

 

[tblaxland]

I don't really like to mess with ISS because it's plane is so far off flat. Seems counterproductive for going anywhere out of Earth's orbit. Like if you wanna go to Mars, you could refuel at ISS, but then waste nearly as much fuel as it took launching into orbit, just to zero your plane. What's up with that? I might change my ISS to an equatorial orbit if I get around to it.

If the ISS was in a lower inclination orbit it would be significantly more difficult for the Russians to launch to it (in fact I would say impossible based on existing tech). Pretty much: no Russians = no ISS. In real life, the ISS was/is never intended to serve as a stopover/refueling station for journeys to other places.

 

[Andy44]

Plus if it were at low inclinations the view would get boring. Astronauts love high-inclination missions because they get to see more than just the tropic regions.

To the OP: Launch MFD is the best thing there is or launching in the correct direction, with assistance from the Align Plane MFD during the ascent. It takes a little practice, but it works. Depending on which launcher you're using, the Launch MFD will even display a marker on the HUD which will guide you in the right pitch angle (that feature doesn't work with all launchers, it depends on how the launcher is coded.)

 

[Kozak]

If the ISS was in a lower inclination orbit it would be significantly more difficult for the Russians to launch to it (in fact I would say impossible based on existing tech).

That's an ignorant saying. Mir IRL has 51.6 deg. inclination, and there were at least two heavy military satellites going >135deg.

 

[Zatnikitelman]

That's an ignorant saying. Mir IRL has 51.6 deg. inclination, and there were at least two heavy military satellites going >135deg.

Um, no he's exactly right. The lowest inclination you can reach is whatever latitude you're on. For Cape Canaveral, it's about 28 degrees, for Baikonur (where the Russians launch) is 45.9 degrees. But I think for ground tracking purposes from Russia itself they launch into the 51.6 degree orbit.

 

[tblaxland]

That's an ignorant saying. Mir IRL has 51.6 deg. inclination, and there were at least two heavy military satellites going >135deg.

So MIR and the ISS have the same inclination (give or take a few hundredths of a degree) IRL. Doesn't that demonstrate my point?

Heavy military sats at inc >135? I wasn't aware of any, but launching due west from Baikonur will get you into a 135deg orbit. So yeah, launching from Baikonur to incs in the range 45 to 135 is possible but I don't think the Soyuz could lift a TMA into a very highly inclined orbit and I don't think it has ever been done. IIRC, STS-36 (inc=62.0) holds the record for the highest inclined man mission.

Zatnikitelman, it is possible to launch to a lower inc than your latitude, but it is propellant costly because you have to head towards the equator and then do a dog-leg turn. Again, not something I think a manned Soyuz could do, but I'm happy to be proven wrong.

 

[Tommy]

An easy way to get a fairly well aligned launch is to use AlignplanesMFD. For a launch when the ISS's orbital path is passing over Cape Canaveral in a notheasterly direction, wait until the TN shown by AlignplanesMFD is about 300, and launch to a heading of 42 degrees.

As soon as possible after you are airborn, get onto the 42 degree heading. If you are in a DG (or similar) as soon as you get airborn back off the throtle and maintain about 200 m/s speed until you are on heading and level the wings. Then Go full throttle and pitch up for the ascent. Your heading will gradually change to a more easterly heading as you ascend - this is normal so don't try to maintain an exactly 42 degree heading throughout the ascent - just keep the roll at zero.

Using this technique I can attain an orbit with less than 2 degrees (usually less than one degree) of RInc with the ISS.

I'll try to find some time to finish the ascent tutorial I've been working on. Keep an eye on the Orbithanger feed for "The Basics) series of tutorials. The first covers launch and ascent in a DG, and will include a manual and two flight recordings showing two different ascent profiles to help you understand how to design an ascent for different types of vessels. Should be out in the next couple weeks. The first will cover ascent to LEO, the second will cover Alignment, Sync, Rendevous, and Docking, and the third will cover Re-entry. No add-ons are used for the first two, Basesync and Aerobrake are used for the re-entry tutorial.

 

[Andy44]

If you are launching from a vertical position, as any realistic rocket add-on does, as well as the shuttle, you have NO WAY to tell which way to roll to get on the proper heading, which is why I recommend Launch MFD. It has a display which tells you what compass direction your dorsal or ventral side is pointing when you are in a vertical attitude, and enables you to make an accurate post-lift-off roll maneuver.

 

[Tommy]

On a non-winged craft such as most rockets, roll angle has no effect on heading. On a DG, or other winged craft any roll angle other than zero or 180 can change your heading and mess up your alignment.

Also, vertically launched vessels such as the shuttle don't stay perfectly vertical for long, and begin pitching down almost immediately after lift off. At any pitch less than exactly 90 degrees, roll angle can be determined and heading adjusted.

This isn't to say that LaunchMFD isn't useful, especially for the more realistic vessels with an extremely tight Delta-V budget.

 

[tblaxland]

On a non-winged craft such as most rockets, roll angle has no effect on heading.

No aerodynamic effect, but it is much harder to do a decent pitch program if you have to pitch and yaw at the same time. In other words, roll so your +Y axis is lying in the target orbital plane, then follow your pitch program.