Aerodynamics of a Projectile Stream 1

[dgerl]

Is there an aerodynamic advantage to launching a stream (series) of small hypervelocity cone-like projectiles (say 1 kg total mass) from Earth surface to Earth orbit vs. one large (1000 kg) mass? Machine gun vs. cannon ball scenario.

The idea is that the initial projectiles will reduce the drag for the following projectiles. It is envisioned that this would sort of form a tunnel up through the atmosphere.

Any comments on this situation would be helpful; this idea is from a few mechanical engineers, so forgive us if we are violating something obvious!

Dean Gerl

 

[IRstuff]

In order for drafting to make much a difference, you have to be essentially kissing the back end of the lead projectile; look at a typical NASCAR race. That's a nightmare for guidance and control.

There are also issues with vortexes and whatnot being shed that the trailing projectiles must go through.

Cones can be horrible shapes to begin with. You might want to start looking at some of the high performance ammo. both commercial and military. There's lots of material on the web. Do a Dogpile on "ogive ballistic" as a start. High performance ammos also have special tail profiling, such as "boattail."

Supersonic rounds are not quite that fancy, e.g., PGU-14 30mm rounds or M735 105mm APFSDS. These tend to have conical noses, but are very tapered and very long to minimize the drag coefficient relative to projectile mass. Density is also important, DU or Tungsten puts more material into a given profile and drag.

TTFN