Flight Question Non-powered landing without correction trun

[lowerlowerhk]

Now I am able to make a unpowered reentry to a runway of KSC with a DGIV, but i have to make a few turns in order to align with the runway. How/when should I adjust my orbital plane so that the runway is immediately aligned after reentry?

 

[Urwumpe]

Don't do it - you need to do S-Turns for bleeding of speed in a controlled way.

 

[agentgonzo]

Choose the orbit that will give you a flight-path that goes close to the target base (aerobrakeMFD or the new MapMFD2 in the latest betas are good for this). Then use bank on your reentry (the DGIV autopilot is good for this) to change your approach so that it goes directly over the base.

You don't need to S-turns if you don't want to.

 

[Urwumpe]

You don't need to S-turns if you don't want to.

but that means you have to have two things right: orbit plane and true anomaly(distance to the base. If you S-turn, it does not matter that much how your orbit plane is like, as long as the distance to the base is right. As long as you can reach the base by cross range capability (And DG and Shuttle can reach quite a lot cross range), the orbit plane is right.

It is much easier to land successfully, if you do S-Turns, as you can prevent over and undershooting better. Doing the same control by changing AOA (over pitch) is much harder.

 

[Zatnikitelman]

Even if you don't use S-Turns, you can still bank to correct your trajectory. S-Turns AFAIK are primarily used to assist in slowing the vehicle down.

 

[ex-orbinaut]

Are you using the Shuttle Fleet add on or the stock Atlantis? The negative acceleration in atmosphere is different for each (surface MFD is useful for seeing this). I am afraid I tweaked the CL for my "stock" Atlantis (as the code is in the SDK folder) so that it comes in nose up and not flat. As the stock "stock" version Atlantis, you can avoid the S turns by starting your reentry at about 70 km alt, 7,000 km from base. Hold off at 65 km until the distance is roughly 3,500 km, then set an approximate rate of descent of between 40 - 55 m/s. Gets you there everytime, with no S turns. Seat of the pants stuff

I personally do not ever aim to come in direct, as arriving over the base with a bit to spare to do a circuit is safer than not having enough (speed or altitude or both). But then, I do not use anything but the standard MFDs (Orbit, Surface and Map). As mentioned above, wait until your orbital path crosses close to your base at the corresponding rwy heading, preferably when the path is about 15º - 20º east of the base when you do the retro burn, as the path will continue to creep west (I use Map for determining this).

Well, it's what I do, Bobby basic, and works for me at any rate.

 

[Linguofreak]

Now I am able to make a unpowered reentry to a runway of KSC with a DGIV, but i have to make a few turns in order to align with the runway. How/when should I adjust my orbital plane so that the runway is immediately aligned after reentry?

You don't. That will take alot of fuel, and you don't need to be aligned beforehand , so it's best just to do the alignment when you get there.

Another way to look at it is that it's easier to turn when you're going slow than when you're going fast, and easier to turn when you're in thick air and can use your wings than when you're in vacuum and have to use your engines. Unless my orbital plane just by pure chance happens to line up with the runway to begin with, I generally don't do a straight-in approach. In the DG XR-1 I generally try to fly over the runway at 20 km and Mach 3, then make a descending 3/4 circle turn (approximately, depending on what angle I'm at to the runway to begin with), to make my alignment. This is approximately how the Shuttle does it in real life.

---------- Post added at 02:40 PM ---------- Previous post was at 02:39 PM ----------

Are you using the Shuttle Fleet add on or the stock Atlantis?

He said he was using a DG-IV.

 

[ex-orbinaut]

He said he was using a DG-IV.

:rofl:Mixed it up with the other similar post....