The Japan Aerosopace Exploration Agency has completed its first series of drop tests in Sweden to validate design techniques for a low-boom supersonic transport, and the results are in
...sonic boom can be cut in half, JAXA says.Photo: Swedish Space Corporation
For the D-SEND 1 campaign at Swedish Space Corp's
Esrange test site in Kiruna, two dart-shaped axisymmetric models were dropped from a high-altitude balloon and their shockwave signatures measured in the air and on the ground and then compared.
One of the models (on the right above) was 5.6m long and shaped to produce a conventional N-wave shockwave signature, which results in a classical “double-bang” sonic boom. The other (on the left) was 8m long and shaped to reduce fore and aft pressure peaks and soften the boom.
For the first test, on May 7, the darts were dropped from the balloon at about 21km altitude and reach Mach 1.43 on their way down. here's the result - the red line showed the N-wave model's (NWM) "double-bang" signature and the blue line the reduced shockwave signature of the shaped axisymmetic low-boom model (LBM).
In the second test, on May 16, the darts were released at 27km and reached Mach 1.7. Here are the results:
There are clear signs that shaping reduced the shockwave pressure peaks. JAXA's next step
is to drop an unpowered model of its planned S3TD silent supersonic technology demonstrator, which is non-symmetrically shaped to minimize both the bow and tail shocks.