Unity Jetblast feeler class

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

// @kurtdekker - part of Jetpack Kurt (Jetpack and SpaceFlight)
//
// intention: informed by throttle, this will activate a particle
// system from a prefab and make a dust spot.
//
// DO NOT ADD to a GameObject.
// Only use the Attach factory function

public class JetblastFeeler : MonoBehaviour
{
    Transform nozzle;
    System.Func<float> GetAmount;
    System.Func<float> GetDistance;

    ParticleSystem ps;
    ParticleSystem.EmissionModule em;

    float multiplier;

    public static JetblastFeeler Attach(
        Transform nozzle,
        System.Func<float> GetAmount,
        System.Func<float> GetDistance)
    {
        JetblastFeeler jf = new GameObject ("JetblastFeeler.Attach()").
            AddComponent<JetblastFeeler> ();

        jf.nozzle = nozzle;
        jf.GetAmount = GetAmount;
        jf.GetDistance = GetDistance;

        GameObject go = Instantiate<GameObject> ( Resources.Load<GameObject>(
            "Prefabs/jetblast_basic_prefab"));

        Transform child = go.transform.GetChild (0);
        jf.ps = child.GetComponent<ParticleSystem> ();
        jf.em = jf.ps.emission;
        jf.multiplier = jf.em.rateOverTimeMultiplier;

        return jf;
    }

    // this is so if it was OFF, when it gets flipped on it gets on
    // one frame later, so it doesn't drag the particle system and
    // spew stray particles around the level
    bool enaDelay;

    void Update()
    {
        bool ena = false;
        float amount = GetAmount ();

        if (amount > 0)
        {
            Vector3 perturbance = Quaternion.Euler( 90, 0, 0) * Random.insideUnitCircle * 0.1f;

            Ray ray = new Ray( nozzle.position, nozzle.forward + perturbance);
            RaycastHit rch;
            if (Physics.Raycast (ray, out rch, GetDistance ())
                && !rch.collider.isTrigger)
            {
                ena = true;

                ps.transform.position = rch.point;
                ps.transform.LookAt (rch.point + rch.normal);

                amount *= (1.0f - rch.distance / GetDistance ());
            }
            else
            {
                amount = 0;
            }
        }

        em.enabled = enaDelay && ena;
        em.rateOverTimeMultiplier = amount * multiplier;

        enaDelay = ena;
    }

    void OnDrawGizmos()
    {
        var pos = nozzle.position;

        var dist = GetDistance();

        var pos2 = pos + nozzle.forward * dist;

        Gizmos.DrawLine( pos, pos2);
    }
}