I've been following the debate between a lot of people about RLV vehicles versus Expendable vehicles.<br /><br />It should be all about the 80/20 rule. If you can divide your cost into two components, one responsible for 80% or your costs and the other responsible for 20% of your costs. You should make sure that the 80% component is minimized before tackling the 20% component.<br /><br />I'll use the spacex falcon 5 rocket as an example.<br /><br />The first stage of the falcon 5 rocket is responsible for about 80% of the total cost of the rocket. 5 Merlin Engines for the first stage versus 1 Merlin engine for the upper stage. I'm assuming that the other components will scale about the same.<br /><br />Note that the first stage is completely reusable. It comes down on parachutes. There is no fancy TPS required because it never reaches a really high velocity and altitude.<br /><br />The second stage is not reusable, but it's not a big portion of the cost, only 20%.<br /><br />Let's look at NASA's new Heavy Launch Vehicle, the one with two SRB and 5 SSME. The SRB are cheap and re-usable, the SSME are expensive and not reusable.<br /><br />So here we are re-using the 20% cost and not re-using the 80% cost.<br /><br />Sorry, but I think they got it backwords.