Detatchable fuel lines using pressure driven oval gear flow meters

[farmerben]

Spoiler

 

 

In order to achieve asparagus staging.

My idea is to create a vertical spline driving a series of stacked oval gear flow meters arranged in a stack.  The ovals in one layer must rotate in a fixed ratio to those in a layer below.  

This creates a governor regulating fuel flow through all the stages of the rocket.  

By itself each rocket must be able to pressurize and deliver all its fuel to its engine (if we want reusability).

There is also a gear train for each inner stage governing that fuel allowed to flow in is exactly the same as fuel flowing out.  

In a 7 stem rocket (6 side boosters and a central stage).  The outer ones also have a gear where the fuel flowing to other stages is exactly equal to  5/2 the fuel flowing to their engine, and the fuel leaving their tank is 7/2.  (for the next stages  5/2 from tank, 3/2 to fuel lines and then  3/2 from tank, 1/2 to fuel lines.

How massive is such a system?  I don't know but the increased dV from asparagus staging is so enormous that a very heavy governor on side boosters that land and are reused can be justified.  

 

 

 

 

 

 

 

[wumpus]

It isn't all that clear how useful asparagus staging would be in real life.  In an ideal case, asparagus staging gives you the thrust of your second (or higher) stage for free.  No more.

In practice, this is ideal for booster/sustainer designs where the sustainer stage can fire "for free" and not carry any excess "empty propellant mass" until it stages.  This really isn't a major factor in going to space (although any extra thrust while your boosters are firing is almost always helpful).  It also means making sure your sustainer nozzle can operate down to sea level (or launch altitude).

From what I understand, a major force in the booster/sustainer model was avoiding in-flight ignition.  Don't expect such a rocket to launch until all boosters are ignited (the TWR isn't high enough).

Asparagus staging got a huge boost from KSP players as KSP has artificially heavy fuel tanks (to compensate for the tiny planet, which in turn reduces the time required to get to orbit).  It also helped that for pre-release versions of KSP, the aerodynamic model favored TWR=2.0 the whole way up.

On the other hand, the Dynetics lander has drop tanks, a technology essentially similar to asparagus staging except it doesn't waste the engines.  This can be used in a manner similar to "bamboo staging" (except that traditional "bamboo staging" is unstable: you have to stop, turn, and eject fuel tanks from the top and not the bottom if you want to make a stable rocket) that allows multiple "stages" to use the same engine (saving both mass and cost on your engines.  Just don't expect much in the way of TWR).

[farmerben]

On 5/3/2020 at 9:41 AM, wumpus said:

It isn't all that clear how useful asparagus staging would be in real life.  In an ideal case, asparagus staging gives you the thrust of your second (or higher) stage for free.  No more.

 

Sorta... but some other details matter.  For example, we can effectively throttle down before Max-Q by separating stages rather than cutting engine power.  Reducing drag at the same time by the way.  In real life we may be chasing a gain of around 1-5% of total dV.  That is still well worth it if the engineering is trustworthy.  

 

I also wanted to mention about oval gear flow meters.  They could be powered by pressurizing the outer boosters.  The pressure on one oval gear mechanism drives the train.  While coupled by shafts we have pressure driven flow control  Upon booster separation the gear shafts can decouple and one is braked.  A braked gear is basically a closed valve. If the fuel lines simply break away from one side of the flowmeter mechanism while the shaft is locked then everything will be fine.  

How much does it weigh?  It must weigh more than purely a pressure driven rocket.  But the rotating machinery may be in similar ballpark to a turbocharger pump, and less than an electrically driven pump.