Acceleration speed spacetrain

If you mean pellets, a fusion propulsion concept could theoretically inject fuel pellets into a fusion chamber. The reaction releases energy, which could ultimately be converted into directed exhaust.

For D–T fusion:

D + T → He-4 + neutron + 17.6 MeV

Fusion/fission reactor

       ↓

Energy conversion

       ↓

Accelerate propellant

       ↓

Very high exhaust velocity

       ↓

High specific impulse

       ↓

Spacecraft gains velocity

𝗧𝗵𝗿𝘂𝘀𝘁

-=>𝗶𝗻𝘀𝘁𝗮𝗻𝘁𝗮𝗻𝗲𝗼𝘂𝘀 𝗮𝗰𝗰𝗲𝗹𝗲𝗿𝗮𝘁𝗶𝗼𝗻

Increasing propulsion force — e.g., stronger linear motors.

Reducing vehicle mass — the same force accelerates a lighter vehicle more.

Reducing opposing forces — less rolling resistance and aerodynamic drag.

Improving magnetic/linear-motor efficiency — more electrical power becomes useful forward force.

Using a longer acceleration track — this doesn't increase the instantaneous acceleration, but gives the vehicle more distance to reach a higher velocity.

Cylinder pressure

Compressed energy

Compressed gas → high pressure → nozzle → high-speed exhaust → thrust → acceleration