If you are the sole leader in the startup, and cash is tight, this is going to be tough.

If you have capable leaders to delegate to, and have a sizeable warchest, this is possible to carry off.

The only way I can see multiple launches working is to have each treated like its own company. Each has its own leader, staff, budget and success/failure criteria in a specific period of time. You act as the cheerleader, focuser and resource-getter for each 'general'.

Trying to do it all yourself will lead to exhaustion.