Chemical rockets work by using an oxidant to burn a fuel and directing the exhaust fumes in one direction. That creates a reaction effect that accelerates the rocket in the opposite direction. They are not very efficient at all. After a few minutes of acceleration, they run out of fuel, making their march velocity very low. Chemical fuels are heavy compared to their energy effect so having more fuel to start with is very expensive. That is why launches cost almost the weight of the payload in gold. Better launches and BTC travel is needed!