my own way of doing reentry timing(is it correct?)

[TMac3000]

Oohh, this is one of my favorite topics:thumbup:

Here's how I do it in DG-IV. There are three major variables (and dozens of minor ones) to be considered: 1) Your ship's mass; 2) Your altitude; 3) The distance to your target. All of these things affect the entry angle and PeA required to reach your target, so predicting a reentry without using Aerobrake MFD or some such is damn near impossible.

I try to start with an altitude between 250 and 300 km.

About 90 degrees after passing my target site, I bring up Aerobrake MFD, go to the map, and do my alignment burn (this saves a whole orbit of waiting).

My preferred distance from the target is 135 degrees. Here I do my deorbit burn. Then roll level with the horizon, and when Aerobrake updates as I pass below 200 km, activate the automatic reentry PRO105SPEC40.

I use constant pitch adjustments to keep the endpoint where I want it. At about Mach 3, just before the autopilot switches off, I arm the gear hydraulics and crossfeed all my remaining RCS propellant into the main tanks. I won't be needing the RCS anymore, and that extra 500 kg can make the difference.

This method usually gets me within 300 km of the base, which is plenty close.

 

[communist]

Oohh, this is one of my favorite topics:thumbup:

Here's how I do it in DG-IV. There are three major variables (and dozens of minor ones) to be considered: 1) Your ship's mass; 2) Your altitude; 3) The distance to your target. All of these things affect the entry angle and PeA required to reach your target, so predicting a reentry without using Aerobrake MFD or some such is damn near impossible.

I try to start with an altitude between 250 and 300 km.

About 90 degrees after passing my target site, I bring up Aerobrake MFD, go to the map, and do my alignment burn (this saves a whole orbit of waiting).

My preferred distance from the target is 135 degrees. Here I do my deorbit burn. Then roll level with the horizon, and when Aerobrake updates as I pass below 200 km, activate the automatic reentry PRO105SPEC40.

I use constant pitch adjustments to keep the endpoint where I want it. At about Mach 3, just before the autopilot switches off, I arm the gear hydraulics and crossfeed all my remaining RCS propellant into the main tanks. I won't be needing the RCS anymore, and that extra 500 kg can make the difference.

This method usually gets me within 300 km of the base, which is plenty close.

my method is quite accurate (in the DGIV) with the atmospheric autoipiliot after i come out of reentry i can fly to my destination

 

[statickid]

is this the wrong way to do this??? if so leave a comment to propose another way

how can it be the wrong way if it works? there are many if not infinite ways to reenter, the most important criteria being:

1. Did you land where you wanted to?

I see you would like people to propose different ways.

A. there is a map trick that I use but it is not very accurate for earth, but very accurate for nonatmosphere places. just retrograde burn until the planet intersection line show up (it used to be pink, haven't payed any attention to what it looks like now) and then adjust the intersection until it is just past the base, then retro near the base. for Earth the pink intersection should be about 20 or 30 degrees PAST the target this will usually give you a short flight home.:thumbup:

 

[Wonderer]

I just trust my intuition when to retro burn and then just cowboy my way down the atmosphere,I'm getting good at it,the last few times I glided to wideawake in the xr2 :hmm:

 

[Tommy]

At about Mach 3, just before the autopilot switches off, I arm the gear hydraulics and crossfeed all my remaining RCS propellant into the main tanks. I won't be needing the RCS anymore, and that extra 500 kg can make the difference.

For me, needing main engines after the de-orbit burn constitutes a FAIL. You've either de-orbited at the wrong distance, failed to manage your velocity correctly, or a combination of the two. Also, I switch RCS off at about 115k (the attitude hold AP can still use RCS, but not the "stick".)

At first, it's a good idea to keep a bit of main fuel, but once you get the hang of it (and have aligned the plane correctly with BaseSync or other method, and use AerobrakeMFD) deadstick landings aren't really that difficult. It does take some practice to figure out where to have the endpoint in Aerobrake - it's not "dead center", but should be 20k (if using a HAC turn of about 270 degrees) to 50k (for a "straight in" approach" from the end of the runway. Transition to "normal" low AoA flight should occur at about 800 m/s velocity and 20k altitude.

Also, the base alignment burn will be more accurate (and often more efficient) if made 90 degrees BEFORE the base, AFTER the de-orbit burn. You'll still be at about 150k alt, plenty high enough to make the burn using the Normal or Anti-Normal AP, and get orientated for re-entry. Even with the new atmosphere model, you don't need to be set for re-entry until you get down below 115k altitude.

 

[hribek]

I use BaseSync MFD for the deorbit burn, like all the time. I also rarely align my orbit with the base using a plane change maneuver. The DGIV seems to have the worst aerodynamic properties of the craft I've used so far - stock DG, shuttle, XR 1 and 2.

It seems to have a higher drag, lower lift and low mass, so I don't find it very useful to use a HAC with the DGIV, it loses speed too fast. Doing straight up approaches with some speedbrake use works best for me.

To sum it up, Shuttle is bad during reentry without an autopilot, but flies great because of high inertia, DGIV has a useful entry autopilot, but it doesn't really fly well in the lower atmosphere. Stock DG can be fun for suborbital flights from KSC to europe and back - go up to 5km/s, open speed brake, hold some 2-5 deg AoA and 0-20m/s sink rate with dynamic pressure up to 10 or 12 kPa. Shuttle-like reentries require AutoFCS or similar.

XR series seems to be coolest of them all, because it isn't trying to hide that it shifts the center of gravity. Though I always wonder if it shifts passengers once you have no fuel aboard

And yes, having to use engines is fail for me as well, except in cases when I'm testing new spacecraft and checking how they fly.

I stopped using Aerobrake MFD in the 2010 version and I moved over to the Glideslope MFD. XR2 can fly an entry profile similar to the shuttle, DGIV cannot.

 

[Shadow Addict]

Waaaaaaait, Glideslope has a HAC display? THAT IS SO AWESOME hurrrr I cannot wait to try it