This is the next generation super-orbital expansion tube after X1.

It is capable of operating at similar conditions to X1 but has a larger diameter (85 mm) facilitating larger models.

The driver section in X2 has a compound piston allowing for a shorter compression tube than would be otherwise necessary.

  • A pilot expansion tube designed and constructed to test concepts for the larger X3 tube
  • Features a compound-piston driver which consists of a light outer piston and a heavier inner piston. The latter separates from the outer piston after some initial compression and the inner piston continues down a smaller diameter compression tube to complete the driver compression process.

The conditions to be expected in the flow assuming equilibrium are given in the following table:

Parameter

Moderate Enthalpy

High Enthalpy (Nitrogen)

Free-stream

Normal Shock

Freestream

Normal Shock

Pressure (kPa)

67

1890

3.3

220

Temperature (K)

4900

8500

4800

11500

Density (kg/m3)

0.046

0.52

0.0022

0.030

Enthalpy (MJ/kg)

27

27

61

61

Velocity (km/s)

6.55

0.6

10.3

0.7

Mach Number

4.8

0.3

7.3

0.2

Diss. fraction N2

-

0.47

0.06

1.0

Ion. fraction N

-

-

-

0.06

X2 was used in 2011 to measure standoff distances at conditions that are representative of re-entry of objects into the earth's atmosphere. As a baseline test case for analytical and CFD modelling, a 60 mm diameter sphere was located in a 10.0 km/s flow and the resulting video is avilable to view here: