In the wikipedia article on solar thermal rockets they write that: "Direct solar heating involves exposing the propellant directly to solar radiation. The rotating bed concept is one of the preferred concepts for direct solar radiation absorption; it offers higher specific impulse than other direct heating designs by using a retained seed (tantalum carbide or hafnium carbide) approach. The propellant flows through the porous walls of a rotating cylinder, picking up heat from the seeds, which are retained on the walls by the rotation. The carbides are stable at high temperatures and have excellent heat transfer properties."

 

What is a retained seed? Is it a crystal?

In the wikipedia article on solar thermal rockets they write that: "Direct solar heating involves exposing the propellant directly to solar radiation. The rotating bed concept is one of the preferred concepts for direct solar radiation absorption; it offers higher specific impulse than other direct heating designs by using a retained seed (tantalum carbide or hafnium carbide) approach. The propellant flows through the porous walls of a rotating cylinder, picking up heat from the seeds, which are retained on the walls by the rotation. The carbides are stable at high temperatures and have excellent heat transfer properties."

 

What is a retained seed? Is it a crystal?

 

The answer is in your question (in parenthesis).

The answer is in your question (in parenthesis).

 

But why is it called a seed?

because thats what they called it. maybe it reminded the guy of some sort of seed dispenser and so he called it that and the name just stuck. this stuff happens.

because thats what they called it. maybe it reminded the guy of some sort of seed dispenser and so he called it that and the name just stuck. this stuff happens.

 

But if the rotating cylinder looks something like this,

then how do the seeds remain on the walls of the cylinder? Why do they not simply fall from the walls and mix with the propellant fluid?

Edited December 9, 200916 yr by Uri

the cylinder is rotating.

 

surely you've been on one of those rides (usually called wall of death or something) where you stand at the wall of a cylinder, it gets spun up and they drop the floor but you remain fixed to the wall thanks to the centrifuge effect.