The risky thing about solids is that you cannot abort them. Once they light, there is no turning them off.
Shuttle always started the main engines for a few seconds (wasting fuel) to make sure the engines worked before lighting the solids. But there were many engine-out scenarios after the solids were lit that would result in loss-of-crew.
There are some ways of turning off solid motors - you cen blow off side panels to drop the pressure inside and either stop combustion or make the thrust negligible.
But tjis was IIRC used on single stick ICBMs and won't be really applicable for anything more delicate.
Solids or no, there were a lot of engine-out scenarios that would cause loss of crew. There were substantial parts of the flight where the orbiter wouldn't have the energy to reach a runway.
And the whole dispersed engine system of the Shuttle made any sort of engine out quite dangerous due to imbalanced thrust. When the engines are all right next to each other it's much more resilient against the failure of one, but the Shuttle would be in trouble if it lost any of it's three legs.
Shuttle always started the main engines for a few seconds (wasting fuel) to make sure the engines worked before lighting the solids. But there were many engine-out scenarios after the solids were lit that would result in loss-of-crew.
But tjis was IIRC used on single stick ICBMs and won't be really applicable for anything more delicate.
And the whole dispersed engine system of the Shuttle made any sort of engine out quite dangerous due to imbalanced thrust. When the engines are all right next to each other it's much more resilient against the failure of one, but the Shuttle would be in trouble if it lost any of it's three legs.