If we need reusable rockets for economy can we afford to put all of our eggs in one basket? Fortunately capitalism encourages innovators to deliver alternative technologies and no one system will hold entire markets forever. Biplanes did eventually let the metal monoplane have a place.
If Spacex delivers part of its hope for economy by point to point flights on earth, it will keep engineers working hard. Consider a space luxury liner making a vertical landing. Boosters are landing this way...most of the time. With 100 crew members, we can expect the FAA and NASA to make certification interesting. When Blue Origin is also planning to vertical land boosters these operations will become pretty common. We hope they have a lot of success because the hope of launch economy rides with them now.
If one wants to predict reliability and safety, statistical math is a useful tool. As the number of engines, operations, and flights rises, a gremlin will appear at some point. One engine failed during a moon launch, but there was enough power from the remaining engines for safety. There must be many redundant systems and available power for landing boosters too.
For a vehicle with 100 people on board, reliable landings are critical. Unlike aircraft, a power loss does not leave one the option to glide to a landing. If a reentry is slowed down enough to prevent burning up in the atmosphere, a rocket will be intact on impact. That could leave a lasting impression on passengers and onlookers on the ground too.
That impact will be more than physical if the business plan is set back. After the shuttle disasters, the program was set back for years. Non-government ventures cannot just throw tax dollars at the solutions. Good engineers will give a warning, but program managers have been known to ignore warnings. If the passion for space overwhelms the desire to survive, someone will not.
Some Mars passion is pushing for a very short hurried timeline. I hope we are not ruining the earth fast enough to justify that. Engineering realities often drive projects a lot slower. This will be especially true when building a man-rated system for 100 passengers and crew. Look at our commercial crew development and expect similar guidance from NASA and the FAA.
I do know that there are a number of ventures ready to offer a wing and a prayer for our space ventures. It is possible to use the physics of the atmosphere to advantage on both the ascent and reentry phase, even on Mars. Spacex and Lockheed Martin both anticipate aerodynamic braking there. A short vertical leg may not be all bad in that case. Our winged ventures are mostly focused on service to LEO and return to earth at this time.
We may remember that the first moon landing was a white knuckle ride. There was little fuel to make a landing in a safe place while they were still moving parallel to the surface. Even a Mars landing will hit the brakes at the last moment. I wonder if that atmosphere could support a runway landing? At least the craft would be horizontal, with landing gear widely spaced. A retro rocket cushion could still to a semi-vertial thrust reversal. Not risking a tall tipsy milk stool landing could be an improvement.
Those are some thoughts for those who can get innovation funded for the next generation designs. We need to train and fund more talent for the enterprise ahead. Perhaps this generation of Kerbal Space adventurers will inspire more creative answers for the future.