Coupla questions...

[Stuger]

Hi all...

I been flying Orbiter for a month now and still got some questions..hope you guys could answer.

1) Vertical landings (somewhere else than Earth) How do you make them? Is there some kinda procedure that would
make it easy? I usually burn my speed off just a little bit before passing the target and see where I gonna land on
the Map MFD. I decrease my speed to almost nothing (to make it safe to approach) then turn at the base which could
still be 100-500km away and try to find it without overshooting which I usually end up doing anyways. The hover
autopilot on DGIII makes the approach alot easier, but it would still be nice to hit the base "right on". Perhaps there
is some descent autopilot for planets without a significant atmosphere?

2) DGIII Reentry autopilot - I just about always have to use hover thrusters to bleed off speed to avoid being blown
up, passengers might not like the high G's :D Even when it's set on level 40 AOA approach. What am I doing wrong?

[Krytom]

When Re-entering make sure that the DGIII's weight is below 19 tonne                                      s (I think that's the
limit, should be in the DGIII manual).

To lower your weight you have to dump fuel. The weight is displayed in one of Dan's wonderful custom HUDs.
Re-entry is difficult, almost everyone thinks so, including me. It isn't impossible though, so good luck.

[DocHoliday]

1) Yup, vertical landings look simple, but aren't really What I usually do, is turn the DGIII around, so I fly backwards
and then burn retrograde to bleed off speed, at the same time either keeping altitude with the Hold autopilot, or
going down at a fixed rate. You could calculate the proper distance, where you need to start breaking, but the
problem is the acceleration increases with time (because you burn fuel and the vessel becomes lighter), so you can at
best approximate it like this:

a=v/t

you get "a" if you briefly press Num +, so the engines go to 100% and you can read it off the dials (the measures is
m/s2)

v, you have to estimate. If you are in a circular orbit, then v doesn't change. If you are in an eliptical orbit, with the
periapsis over the landing site, your v will be highest over the target. There is a formula to calculate that to, but I
don't remember it. Anyway, if you're around Moon, you can just measure it, making a pass over the target and
landing the next time around. Okay, so you have a and v. For the sake of argument, let's say the DGIII breakes at
15m/s2 and has an average velocity of 1500m/s. So it will take v/t seconds to come to a halt. t=100s. So now you
have to estimate when to start the burn. You can assume your velocity will drop in a straight line (linearly), even
though in fact it will not (it will drop in an accelerated fashion, but we'll disregard it). You calculate the distance at
which you should burn like this:

s=a*t*t=150000m=150km (actually I'm not sure about this part, but can't test now), so this is basically how far from
target you should start burning your main engine in retrograde direction You should come to a full stop a little
before the pad (because the acceleration increases slightly over time), but you can always cut engines a little sooner
and drift along. Better than overshooting

There are two other easier ways:
- ArriveMFD, which does approximatelly the same thing only automatically and more accuratelly
http://www.orbithangar.com/searchname2.cfm?search=arrive

- LunarLandingMFD which does this and actually lands your craft on the landing pad too. And it is freaky how accurate
it is. It's still in the testing phase, but you can ask for it here:
http://orbit.m6.net/v2/read.asp?id=19837

There are probably other methods. Like flying by the seat of your pants, but I don't like putting my passengers in
such situations

Cheers,
Janez

[Simonpro]

DocHoliday wrote:
...s=a*t*t=150000m=150km...

Isn't it s=0.5*a*t^2?

[DocHoliday]

Hm.. But of course, dropping linearly, makes an average of 1/2. Thanks!

Make that 75km away from landing site then



Post Edited ( 03-01-05 10:46 )