Towards a reusable rocket system with a fast turnaround, revisited

Speculation alert

Even though Elon Musk has tweeted that he has a solution for his re-usability goal, the attractiveness of this idea still fascinates me.  Not likely that this would ever happen, but fun to think about.

So I played around with the numbers a bit.  It may be desirable to use the beamed energy only as a booster stage, or a first stage standalone.  I figured that a 150 ton wet mass rocket would be all that it would take to get to orbit.  That's less than half the mass of the Falcon 9 with full re-usability and flexible design potential.

The first stage would accelerate to about 4000 mph and then release the second stage which would take it to orbit.  I figured about 100 tons for the second stage and payload.  There aren't any hard numbers for the second stage Falcon 9 masses, so I guessed that it would be less than 100 tons.  One hundred tons would be over 25% of the full wet mass of the entire Falcon 9.  The second stage probably doesn't weigh that much.  The additional margin provided by the device would go toward making the second stage re-usable.

All of this is a wild guess since I don't have the numbers.  But with the additional capability- a thrust to weight ratio comparable to a chemical rocket, and an ISP of 850- the amount of additional leeway allows for a lot of room to adjust the numbers.  Those kind of numbers give design flexibility, thus feasibility in this regard shouldn't be the issue.

I'm guess that the current configuration separates at 4000 mph, so this mythical configuration could do the same thing as far as trajectory is concerned, that's all I'm saying.

The first stage would fly back as a RTLS module, probably as a glider, or a lightly powered aircraft.  Since the numbers for Parkin's device allow for a 20% structural margin, this should pose no difficulty.  The device allows for 35% payload fraction, if you count the flyback module and remaining wet mass of the second stage and Dragon capsule.

It would liftoff and land like the Shuttle did.

Would it look like the Shuttle?  Perhaps, perhaps not.  One thing that may give some unease is to have a powerful microwave aimed at a rocket stack.  Maybe you'd like to have the first stage shielding the second stage and payload.  That would mean a sidemount configuration.  If that is not desirable, then some other configuration may be employed.

Those details are probably too speculative even for this speculative post.  So, I'll leave that discussion at this point.  The main point is the wet mass of the entire configuration and the available of design flexibility to make it re-usable.

A second point is by using the beamed power only as a first stage, the power requirements would be a lot less.  You'd be less ambitious in altitude and acceleration than Parkin's original proposition, so it would take a lot less energy to get to 4000 mph than to orbital velocity.  You'd stay well within range of the microwave beam.  That part poses less of a challenge.  Not to mention that the design would allow for manned flights, as the original configuration didn't.

Update:

Next in Series, Part 3