To give an interstellar missile sufficiently high maneuverability and acceleration, relying on chemical fuel is clearly not feasible.
The only viable solution is to install a secondary pressurized thruster inside the missile to propel it forward.
However, the largest interstellar missile is only about five or six tons, and the smallest is a few hundred kilograms. Installing a secondary pressurized thruster into such a small missile body is almost impossible.
After successfully miniaturizing the secondary pressurized thruster enough to be installed in a Mercury-class battleship, Tom still diligently continued his research on its miniaturization.
During this period, Tom did make some progress, further optimizing its performance, reducing its mass and volume, but it was still far from being able to be installed in a missile.
Perhaps with his technological advancement, this might be possible in the future, but it is clearly impossible in the short term.
