BTC: BurnTimeCalcMFD v1.1 (C) 2004 by David Henderson -- orbiter@aibs.org.uk
     BurnTimeCalcMFD v1.2 (C) 2005 by Chris Jeppesen -- chrisj@kwansystems.org
     BurnTimeCalcMFD v1.3 (C) 2006 by Chris Jeppesen -- chrisj@kwansystems.org
     BurnTimeCalcMFD v1.4x(C) 2007 by Thomas Hagemeyer -- thomas.hg@web.de
     BurnTimeCalcMFD v1.5 (C) 2007 by kwan3217         -- ??
     BurnTimeCalcMFD v2.0 (C) 2007 by Thomas Hagemeyer -- thomas.hg@web.de
	 BurnTimeCalcMFD v2.4 (C) 2013 by Dimitris Gatsoulis (dgatsoulis)
	 BurnTimeCalcMFD v2.5 (C) 2014 by Szymon Ender (Enjo) -- ender-sz@go2.pl
	 BurnTimeCalcMFD v2.6 (C) 2014 by Szymon Ender (Enjo) -- ender-sz@go2.pl
	 BurnTimeCalcMFD v2.7 (C) 2014 by Szymon Ender (Enjo) -- ender-sz@go2.pl


BurnTimeCalcMFD (BTC) is a companion for TransX or any other transfer MFD that
gives you your required dV for transfer orbit insertion, and time to periapsis
(PeT) but not time to start burning.

Using a simple first-order approximation of the mass decrease of your vessel
BurnTimeCalcMFD calculates the time required to achieve the specified dV (you
may read this off TransX's insertion display and enter it using the keys below).

It also calulates the time required to produce half this velocty change to give
you an approximate time to periapsis (PeT) to start your prograde (or retro-)
burn.

I've found it reliably gets me into a transfer with less than 1 degree offset
between semi major axes using DeltaGlider and Fregat. Obviously it's only an
approximation, however.


LIMITATIONS
===========

BTC assumes you will be using 100% throttle for the burn.

BTC cannot take MULTISTAGE burns into account. That is, you cannot change your
empty weight during the burn.

INSTALLATION
============

Unpack in your Orbiter folder, using folder names. Using the Modules tab
in the Launchpad, activate BurnTimeMFD.

You also need ModuleMessaging library, available under:
http://www.orbithangar.com/searchid.php?ID=6412

INSTRUCTIONS
============

The timer in BTC runs in three different modes: Periapse, Apoapse, and Manual.
Naturally, in a hyperbolic orbit with no apoapse, Apoapse mode will be disabled.
To switch between modes, use SHIFT_M. The current mode is highlighted in 
yellow. When manual is both the active mode and the current variable, it
is bright yellow. When it is only the active mode, it is dim yellow. When
it is only the current variable, it is white, and when it is neither, it
is gray.

Bring up TransX with the Escape Plan properly configured. You will
be given a required dV (delta-velocity) and PeT (time to pereiapsis). Bring
up BTC.

Use SHIFT_G (or GET button) to capture the values. If the time is negative, 
it will be ignored.

You can also capture TransX' Manoeuvre mode variables with SHIFT_G.

If you want to do an Autoburn, use SHIFT_PERIOD to switch variables. Set the 
manual delay to something less than the current PeT shown in TransX. When
the PeT shown in TransX exactly matches the manual delay, press SHIFT_A. This 
arms the Autoburn. The green timing calculations are replaced by a yellow
countdown timer. Notice that this countdown is less than the specified PeT
and manual delay, as it takes into account the "Engage at T-minus" calculation.

Once the Autoburn is armed, no changes are possible to the dV magnitude or 
manual timing. To abort an Autoburn before the yellow countdown reaches zero, 
just push SHIFT_A again. This will cancel the burn. You may then freely 
re-adjust the burn parameters.

You will now need to turn PROGRADE (for an eject -- RETRO for a capture).
BTC never takes control of the vessel attitude. You remain steerable before,
during, and after the burn.

If you want to manually burn, start your burn at the PeT time indicated by BTC.

If you do an Autoburn, the burn will automatically start when the yellow 
countdown reaches zero. The yellow countdown will then be replaced by a red
countdown to engine shutdown. To abort the burn after it starts, press SHIFT_A.

For a manual burn, kill the engines when dV = 0 ON THE TRANSX DISPLAY. An
Autoburn should cut them automatically, and very accurately.

You should only me a small angle off the correct orbit. You may correct this
by thrusting 90 degrees inwards or or outwards briefly. Do this soon after
completing your burn, it saves fuel this way.

Finally adjust your dV and SemiMajor offset values down to as close to zero
as pratical with the LINEAR RCS mode.

AUTOCIRC
========

The new Autocirc feature makes certain maneuvers like lunar orbit insertion,
OMS-2, and geostationary orbit insertion, easy. It calculates the necessary
DeltaV and timing to circularize the orbit at one of the apsides. To use 
Autocirc, first select the correct apse with SHIFT_M. Then, push SHIFT_C.
That's all there is to it! 

Just make sure to have the craft in the correct orientation, 
prograde or retrograde, when the burn starts. You want to use prograde at 
apoapse, and retrograde at periapse.

The Autocirc feature continually recalculates the timing based on the 
current vessel state vector, to account for perturbations due to 
third-body effects or non-spherical gravity.

UNITS
=====

The Burn time calculator can now be made to work in either SI units (kg,N,s,m)
or in US units (lbm,lbf,s,ft). Some historical ships like the Space Shuttle
or older US ships work natively in US units, so this allows inter-operation with
that kind of ship to flow more easily. 

To switch units, push the UNT button.

Good luck!

David "dh219/Hendo" Henderson.
orbiter@aibs.org.uk
http://www.aibs.org.uk/orbiter/

Chris Jeppesen
chrisj@kwansystems.org

Thomas Hagemeyer
topperte301@arcor.de
KEYSTROKES
==========

All keystrokes require SHIFT.

- (or _): decrease dV or manual time by adjustment factor
= (or +): increase dv or manual time by adjustment factor

[ (or {): Multiply adjustment factor by 10
] (or }): Divide adjustment factor by 10

, (or <): Switch from dV to manual time and back
. (or >): Switch from dV to manual time and back

BACKSPACE: reset to zero

M: Change timing mode to next mode

A: Arm the Autoburn timer with the current dV and timing mode
   or cancel a previous Autoburn.

C: Calculate a circularization maneuver at the currently selected
   apse (switch with M, action when used on manual burn time is undefined).
   and arm the Autocirc timer with the correct dV and timing mode.

L: Fire the engines for the full time calculated, starting
   right now.

E: Select Engine: Main, Hover or Retro

U: Switch units: SI or US

(new from 2.5)
G: Get values from TransX' Escape Plan or Manoeuvre Mode

==============
v1.1 COPYRIGHT
==============

BurnTimeCalc, the code, modules and configurations are copyright 2004
David Henderson and released under the terms of the GNU LGPL (see
enclosed LGPL.TXT) with the exception of the MaverickTech thruters
libraries Titled Mav*.h Mav*.cpp which are copyright 2003 Russell
Smith and may not be used or distributed without due credit to R Smith
and without enclosing the full source.

==============
v1.2, v1.3 COPYRIGHT
==============

Version 1.2, the code, modules and configurations are copyright 2005
Chris Jeppesen and continue to be under the terms of the GNU LGPL (see
enclosed LGPL.TXT). All MaverickTech code has been removed.

Version 1.3, the code, modules and configurations are copyright 2006
Chris Jeppesen and continue to be under the terms of the GNU LGPL (see
enclosed LGPL.TXT).

==============
v1.4, v1.41 COPYRIGHT
==============

Version 1.4, the code, modules and configurations are copyright 2007
Thomas Hagemeyer and continue to be under the terms of the GNU LGPL (see
enclosed LGPL.TXT).

==============
v1.5 COPYRIGHT
==============

Version 1.5, the code, modules and configurations are copyright 2008
Chris Jeppesen and continue to be under the terms of the GNU LGPL (see
enclosed LGPL.TXT).
