Cosmos in the Classroom

Hexagon Lab 2.1: Analyzing Rocket Ascent Data

Vertical velocity data from a sounding rocket exhibit piecewise-linear segments corresponding to thrust-on and thrust-off regimes. The slope of each segment indicates acceleration: steep positive slope during burn, approximately −g during ballistic flight.

Course: HPHYS
Unit: 2
Purpose

Use velocity–time data from a sounding rocket ascent to identify flight phases and compute accelerations by interpreting the slope of the v–t graph.

Materials
  • Velocity–time dataset from a NASA sounding rocket launch (vertical component)
  • Graphing tool (digital or paper)
  • Calculator
  • Research Log / Science Notebook
Investigation 1: Engine Burn Phase Analysis
  1. Plot the velocity–time data for the first 20 seconds. Describe the shape of this portion of the graph.
  2. Calculate the acceleration during this phase using Δv/Δt between (t = 0 s, v = 0 m/s) and (t = 20 s, v = 784 m/s).
    Hint: Slope of v–t graph equals acceleration.
    a = (784 − 0) / (20 − 0) m/s^2
  3. Compare this acceleration to ag = 9.80 m/s^2 (free fall). What does the magnitude imply about engine thrust during this phase?
  4. CER Prompt — What evidence indicates that the rocket engine is operating during the first 20 seconds?
Investigation 2: Engine Cutoff and Ballistic Phase
  1. Examine the velocity data after t = 20 s. What change do you observe in the pattern of the values?
  2. Calculate the acceleration during 20–30 s using Δv/Δt between (t = 20 s, v = 784 m/s) and (t = 30 s, v = 686 m/s).
    Hint: Expect magnitude near g with negative sign.
    a = (686 − 784) / (30 − 20) m/s^2
  3. CER Prompt — How does the velocity pattern change at t = 20 s, and what does this reveal about engine operation?
Investigation 3: Predicting Apogee
  1. During ballistic flight, use v1 = v0 + aΔt with v1 = 0 at apogee.
    v1 = v0 + aΔt
  2. With v0 = 784 m/s (at cutoff) and a = −9.80 m/s^2, solve for Δt to apogee.
  3. Compute absolute apogee time as t_apogee = 20.0 s + Δt.
Topics: