diff --git a/src/orbits.cpp b/src/orbits.cpp
index 9ee1fee..b5e0560 100644
--- a/src/orbits.cpp
+++ b/src/orbits.cpp
@@ -52,33 +52,6 @@ ellipseInitAE(double a, double e)
 	return ellipseInitAB(a, b);
 }
 
-double
-ellipseGetEccentricity(double a, double p)
-{
-	return sqrt(1 - p / a);
-}
-
-bool
-ellipseValidate(const EllipseParameters& ep)
-{
-	// TODO: find out why satellite position gets wonky with orbit
-	// 	eccentricity > 0.995 while passing through true anom = 0.
-	// 	maybe divide by 0, or some floating point error?
-	return (ep.a > 0 &&
-		ep.b > 0 &&
-		ep.a >= ep.b &&
-		ep.e >= 0 &&
-		ep.e < 0.995);
-}
-
-bool
-ellipsesEqual(EllipseParameters& e1, EllipseParameters& e2)
-{
-	return (e1.a == e2.a &&
-		e1.b == e2.b &&
-		e1.e == e2.e);
-}
-
 Ellipse3D
 ellipseInit3D(EllipseParameters ep, uint vert_count)
 {
@@ -104,72 +77,6 @@ orbitInit(double a, double e)
 	return o;
 }
 
-double
-orbitGetRadialDistance(double e, double p, double true_anom)
-{
-	return p / (1 + e * cos(true_anom));
-}
-
-double
-orbitGetAngularMomentum(double p, double mu)
-{
-	return sqrt(mu * p);
-}
-
-double
-orbitGetSemiMajorAxis(double epsilon, double mu)
-{
-	return -1 * mu / (2 * epsilon);
-}
-
-double
-orbitGetSemiLatusRectum(double h, double mu)
-{
-	return pow(h, 2) / mu;
-}
-
-double
-orbitGetAngularMomentumFromStateVectors(double r, double v, double gamma)
-{
-	return r * v * cos(gamma);
-}
-
-double
-orbitGetSpecificEnergy(double a, double mu)
-{
-	return -1 * mu / (2 * a);
-}
-
-double
-orbitGetSpecificEnergyFromStateVectors(double r, double v, double mu)
-{
-	return pow(v, 2) / 2 - mu / r;
-}
-
-double
-orbitGetVelocity(double epsilon, double mu, double r)
-{
-	return sqrt(2 * (epsilon + mu / r));
-}
-
-double
-orbitGetFlightPathAngle(double e, double true_anom)
-{
-	return atan(e * sin(true_anom) / (1 + e * cos(true_anom)));
-}
-
-double
-orbitGetPeriod(double a, double mu)
-{
-	return 2 * M_PI / sqrt(mu) * sqrt(pow(a, 3));
-}
-
-glm::vec2
-polarToRect(double angle, double r)
-{
-	return glm::vec2(r * cos(angle), r * sin(angle));
-}
-
 void
 ellipse3DUpdate(EllipseParameters ep, Ellipse3D& e3d)
 {
@@ -189,50 +96,50 @@ ellipse3DUpdate(EllipseParameters ep, Ellipse3D& e3d)
 //
 
 // FIXME: variable names 'ecc' should be just 'e'
-double
+inline double
 getEccAnomFromTrueAnom(double ecc, double true_anom)
 {
 	return 2 * atan(sqrt((1 - ecc) / (1 + ecc)) * tan(true_anom / 2));
 }
 
-double
+inline double
 getTrueAnomFromEccAnom(double ecc, double ecc_anom)
 {
 	return 2 * atan(sqrt((1 + ecc) / (1 - ecc)) * tan(ecc_anom / 2));
 }
 
-double
+inline double
 getMeanAnomFromEccAnom(double ecc_anom, double ecc)
 {
 	return ecc_anom - ecc * sin(ecc_anom);
 }
 
-double
+inline double
 getMeanMotion(double mu, double a)
 {
 	return sqrt(mu / pow(a, 3));
 }
 
-double
+inline double
 getPropagatedMeanAnom(double mean_anom, double mean_motion, double time_step)
 {
 	return mean_anom + mean_motion * (time_step);
 }
 
-double
+inline double
 getInitialTrialValue(double mean_anom, double ecc)
 {
 	return mean_anom + ecc * sin(mean_anom)
 		+ ((pow(ecc, 2) / 2) * sin(2 * mean_anom));
 }
 
-double
+inline double
 getTrialError(double ecc, double test_anom, double mean_anom)
 {
 	return test_anom - ecc * sin(test_anom) - mean_anom;
 }
 
-double
+inline double
 getNextTrialValue(double err, double ecc, double test_anom, double mean_anom)
 {
 	// compute derivative of the error function
@@ -288,7 +195,7 @@ getPropagatedTrueAnomaly(TwoBodySystem sys,
 // FIXME: organize into interface/internal functions
 
 // NOTE: return an equivalent angle between 0 and 2 pi radians
-double
+inline double
 orbitClampAngle(double theta)
 {
 	double revs = floor(theta / (2 * M_PI));
diff --git a/src/orbits.h b/src/orbits.h
index c9ed76c..83c41c4 100644
--- a/src/orbits.h
+++ b/src/orbits.h
@@ -82,14 +82,32 @@ ellipseInitAB(double a, double b);
 EllipseParameters
 ellipseInitAE(double a, double e);
 
-double
-ellipseGetEccentricity(double a, double p);
-
-bool
-ellipseValidate(const EllipseParameters& ep);
+inline double
+ellipseGetEccentricity(double a, double p)
+{
+	return sqrt(1 - p / a);
+}
 
-bool
-ellipsesEqual(EllipseParameters& e1, EllipseParameters& e2);
+inline bool
+ellipseValidate(const EllipseParameters& ep)
+{
+	// TODO: find out why satellite position gets wonky with orbit
+	// 	eccentricity > 0.995 while passing through true anom = 0.
+	// 	maybe divide by 0, or some floating point error?
+	return (ep.a > 0 &&
+		ep.b > 0 &&
+		ep.a >= ep.b &&
+		ep.e >= 0 &&
+		ep.e < 0.995);
+}
+
+inline bool
+ellipsesEqual(EllipseParameters& e1, EllipseParameters& e2)
+{
+	return (e1.a == e2.a &&
+		e1.b == e2.b &&
+		e1.e == e2.e);
+}
 
 // NOTE: create vertices for a 3d ellipse
 // NOTE: all vertices are in the x/y plane with z = 0
@@ -102,14 +120,72 @@ ellipse3DUpdate(EllipseParameters ep, Ellipse3D& e3d);
 OrbitalElements
 orbitInit(double a, double e);
 
-double
-orbitGetVelocity(double epsilon, double mu, double r);
+inline double
+orbitGetAngularMomentum(double p, double mu)
+{
+	return sqrt(mu * p);
+}
 
-double
-orbitGetFlightPathAngle(double e, double true_anom);
+inline double
+orbitGetSemiMajorAxis(double epsilon, double mu)
+{
+	return -1 * mu / (2 * epsilon);
+}
 
-double
-orbitGetPeriod(double a, double mu);
+inline double
+orbitGetSemiLatusRectum(double h, double mu)
+{
+	return pow(h, 2) / mu;
+}
+
+inline double
+orbitGetAngularMomentumFromStateVectors(double r, double v, double gamma)
+{
+	return r * v * cos(gamma);
+}
+
+inline double
+orbitGetSpecificEnergy(double a, double mu)
+{
+	return -1 * mu / (2 * a);
+}
+
+inline double
+orbitGetSpecificEnergyFromStateVectors(double r, double v, double mu)
+{
+	return pow(v, 2) / 2 - mu / r;
+}
+
+inline double
+orbitGetVelocity(double epsilon, double mu, double r)
+{
+	return sqrt(2 * (epsilon + mu / r));
+}
+
+inline double
+orbitGetFlightPathAngle(double e, double true_anom)
+{
+	return atan(e * sin(true_anom) / (1 + e * cos(true_anom)));
+}
+
+inline double
+orbitGetPeriod(double a, double mu)
+{
+	return 2 * M_PI / sqrt(mu) * sqrt(pow(a, 3));
+}
+
+// NOTE: aka) the trajectory equation (eq. 2.45)
+inline double
+orbitGetRadialDistance(double e, double p, double true_anom)
+{
+	return p / (1 + e * cos(true_anom));
+}
+
+inline glm::vec2
+polarToRect(double angle, double r)
+{
+	return glm::vec2(r * cos(angle), r * sin(angle));
+}
 
 void
 orbitUpdate(OrbitalElements& o, double a, double e);
@@ -153,30 +229,5 @@ getPropagatedTrueAnomaly(TwoBodySystem sys,
 	double initial_anom,
 	double time_step);	// NOTE: in seconds
 
-// NOTE: aka) the trajectory equation (eq. 2.45)
-double
-orbitGetRadialDistance(double e, double p, double true_anom);
-
-double
-orbitGetAngularMomentum(double p, double mu);
-
-double
-orbitGetSemiMajorAxis(double epsilon, double mu);
-
-double
-orbitGetSemiLatusRectum(double h, double mu);
-
-double
-orbitGetAngularMomentumFromStateVectors(double r, double v, double gamma);
-
-double
-orbitGetSpecificEnergy(double a, double mu);
-
-double
-orbitGetSpecificEnergyFromStateVectors(double r, double v, double mu);
-
-glm::vec2
-polarToRect(double true_anom, double r);
-
 double
 orbitGetTimeOfFlight(TwoBodySystem sys, double theta_begin, double theta_end);