diff --git a/ascent.ks b/ascent.ks
index dada18f..949d427 100644
--- a/ascent.ks
+++ b/ascent.ks
@@ -1,5 +1,7 @@
 // Inital gravity turn
+// #include staging
 run once staging.
+// #include maneuver
 run once maneuver.
 
 function doAscentSteering {
@@ -10,6 +12,7 @@ function doAscentSteering {
   lock steering to tarSteer.
   until ship:velocity:surface:mag >= 100 {
     set tarSteer to heading(heading, 90 - (ship:velocity:surface:mag / 10)).
+    if defined UPDATE_LOG { UPDATE_LOG(). }
     wait 0.
   }
 
@@ -53,13 +56,18 @@ function basicAscent {
   doAscentSteering(heading).
 
   // coast to apoapsis
-  wait until ship:apoapsis >= targetAltitude.
+  until ship:apoapsis >= targetAltitude {
+    if defined UPDATE_LOG { UPDATE_LOG(). }
+  }
   lock steering to ship:prograde.
   lock throttle to 0.
 
   // don't do futher calcs until out of the atmosphere or very close to apoapsis
-  wait until ship:altitude >= body:atm:height or eta:apoapsis < 60.
+  until ship:altitude >= body:atm:height or eta:apoapsis < 60 {
+    if defined UPDATE_LOG { UPDATE_LOG(). }
+  }
 
   executeNode(createCircularizationNode()).
+
   print "Circularized".
 }
\ No newline at end of file
diff --git a/boot/boot.ks b/boot/boot.ks
index e98fc2b..2536d0c 100644
--- a/boot/boot.ks
+++ b/boot/boot.ks
@@ -1,11 +1,52 @@
 copyPath("0:/ascent.ks", "1:/ascent.ks").
 copyPath("0:/maneuver.ks", "1:/maneuver.ks").
 copyPath("0:/staging.ks", "1:/staging.ks").
+copyPath("0:/logger.ks", "1:/logger.ks").
+// #include logger
+run once logger.
+// #include ascent
 run once ascent.
 
+createDir("1:/logs").
+set LOG to loggerCreate(
+  "1:/logs/flight-" + ship:shipName + "-" + time:full + ".json",
+  list(
+    "time",
+    "altitude",
+    "apoapsis",
+    "periapsis",
+    "eccentricity",
+    "throttle",
+    "pitch",
+    "heading",
+    "mass",
+    "stageNum"
+  ),
+  1.0
+).
+set LOG_DATA to {
+  return list(
+    time:seconds,
+    round(ship:altitude, 1),
+    round(ship:apoapsis, 1),
+    round(ship:periapsis, 1),
+    round(ship:orbit:eccentricity, 4),
+    round(ship:throttle, 3),
+    round(ship:pitch, 2),
+    round(ship:heading, 2),
+    round(ship:mass, 3),
+    stage:number
+  ).
+}.
+
+function UPDATE_LOG {
+  loggerUpdate(LOG, LOG_DATA()).
+}
+
 wait until ship:unpacked.
 core:part:getmodule("kOSProcessor"):doevent("Open Terminal").
 
 basicAscent(90, 80000).
 
-core:part:getmodule("kOSProcessor"):doevent("Close Terminal").
\ No newline at end of file
+core:part:getmodule("kOSProcessor"):doevent("Close Terminal").
+loggerFlush(LOG).
\ No newline at end of file
diff --git a/logger.ks b/logger.ks
new file mode 100644
index 0000000..e8bf3af
--- /dev/null
+++ b/logger.ks
@@ -0,0 +1,84 @@
+// ═══════════════════════════════════════════════════════════
+// logger.ks
+// CSV logger with buffered writes.
+//
+// Usage:
+//   local log to loggerCreate("0:/logs/flight.csv", list("time", "altitude", "apoapsis")).
+//   loggerUpdate(log, list(time:seconds, altitude, apoapsis)).
+//   loggerFlush(log).   // call at end of script to flush remaining buffer
+// ═══════════════════════════════════════════════════════════
+
+// ── Creates a logger and writes the CSV header.
+// Parameters:
+//   filePath    : string  — destination path, e.g. "0:/logs/flight.csv"
+//   columns     : list    — ordered list of column name strings
+//   flushPeriod : scalar  — seconds between buffer flushes (default 1.0)
+// Returns a logger lexicon to be passed to loggerUpdate / loggerFlush.
+function loggerCreate {
+	parameter filePath.
+	parameter columns.
+	parameter flushPeriod is 1.0.
+
+	// Create or overwrite the file and write the header row
+	local f to open(filePath).
+	f:clear().
+	f:writeln(_loggerFormatRow(columns)).
+
+	local logger to lexicon(
+		"file",        f,
+		"columns",     columns,
+		"buffer",      list(),
+		"flushPeriod", flushPeriod,
+		"lastFlush",   time:seconds
+	).
+
+	return logger.
+}
+
+// ── Appends a data row to the buffer.
+// Values must be in the same order as the columns list passed to loggerCreate.
+// Flushes the buffer to disk if the flush period has elapsed.
+function loggerUpdate {
+	parameter logger.
+	parameter values.
+
+	logger["buffer"]:add(_loggerFormatRow(values)).
+
+	if time:seconds - logger["lastFlush"] >= logger["flushPeriod"] {
+		loggerFlush(logger).
+	}
+}
+
+// ── Flushes all buffered rows to disk immediately.
+// Call at the end of a script to ensure no data is lost.
+function loggerFlush {
+	parameter logger.
+
+	local f to logger["file"].
+	local buf to logger["buffer"].
+
+	local i to 0.
+	until i >= buf:length {
+		f:writeln(buf[i]).
+		set i to i + 1.
+	}
+
+	buf:clear().
+	set logger["lastFlush"] to time:seconds.
+}
+
+// ── Formats a list of values as a CSV row string.
+function _loggerFormatRow {
+	parameter values.
+
+	local row to "".
+	local i   to 0.
+
+	until i >= values:length {
+		if i > 0 { set row to row + ",". }
+		set row to row + values[i].
+		set i to i + 1.
+	}
+
+	return row.
+}
\ No newline at end of file
diff --git a/maneuver.ks b/maneuver.ks
index 2323e61..5422085 100644
--- a/maneuver.ks
+++ b/maneuver.ks
@@ -1,3 +1,12 @@
+// ═══════════════════════════════════════════════════════════
+// maneuver.ks
+// Utility functions related to maneuvers.
+//
+// Usage:
+//   executeNode(nd: node)
+// ═══════════════════════════════════════════════════════════
+
+// #include staging
 run once staging.
 
 function executeNode {
@@ -59,6 +68,7 @@ function executeNode {
 			lock throttle to min(1, dvLive:mag / maxAcc).
 		}
 
+    if defined UPDATE_LOG { UPDATE_LOG(). }
 		wait 0.
 	}
 
diff --git a/staging.ks b/staging.ks
index 63bfc85..f6e8803 100644
--- a/staging.ks
+++ b/staging.ks
@@ -1,3 +1,12 @@
+// ═══════════════════════════════════════════════════════════
+// staging.ks
+// Utility functions related to staging and the effects of changing stages
+//
+// Usage:
+//   basicStaging()
+//   calcBurnTime(dvNeeded: scalar)
+// ═══════════════════════════════════════════════════════════
+
 
 declare function basicStaging {
   when ship:maxThrust = 0 then {