Recovery methods for reusable lifters (RSS)

[Armchair Rocket Scientist]

In "stock" KSP, I've generally used reusable launchers whenever possible, but I was generally content to just fit the lower stages with parachutes and let them splash down. Now that I've installed RSS, I want to keep making reusable vehicles, but with all the constraints that would apply to a real one. However, I've been having some difficult figuring out the most efficient method of bringing the spent stages down.

Here's what I have so far:

Parachute splashdown:

- high-mass ratio stage still must perform burn at landing to survive impact.

+ Parachutes save 300 m/s maximum, weigh approx. 1 t for 20 t stage (at 20 m/s descent). Equivalent fuel would weigh approx. 2 t.

- High maintenance costs due to salt water exposure.

- added complexity, risk of parachute failure.

*+ only feasible method for SRBs, which are also more durable, less susceptible to water damage.

Boostback, parachute landing: not feasible - unsteerable parachutes do not offer sufficient precision for safe touchdown.

Propulsive splashdown:

+ low dV requirements as only landing, possible small braking burn used.

- High maintenance costs due to salt water exposure.

Boostback, propulsive landing:

- very high dV requirements, likely over 2 km/s.

+ Allows for very fast turnaround, no transport costs.

- In practice, turnaround time from transport will be minimal compared to time from inspection, maintenance, and payload integration.

*- dV requirements prohibitive for central core of multi-core variants (possibly variants with many SRBs as well).

*+ dV requirements lower for outer cores of multi-core variants.

Parafoil to splashdown:

+ low dV requirements.

+ Parafoils provide cross-range capability with no fuel use.

Landing occurs horizontally, with low vertical speed but high horizontal speed. Inflatable pontoons would allow safe landing, minimize saltwater exposure.

- Parafoils, steering system, landing gear very heavy & add complexity.

- Difficult to make parafoils redundant.

Boostback, parafoil landing:

- very high dV requirements, likely over 2 km/s.

+ allows for very fast turnaround, no transport costs.

+ parafoils provide cross-range capability with no fuel use.

Landing occurs horizontally, with low vertical speed but high horizontal speed. Deployable skids or wheels would allow runway landing.

- parafoils, steering system, landing gear very heavy & add complexity.

- difficult to make parafoils redundant.

*- dV requirements prohibitive for central core of multi-core variants (possibly variants with many SRBs as well).

*+ dV requirements lower for outer cores of multi-core variants.

Downrange propulsive landing:

+ low dV requirements without saltwater exposure.

- requires one or more floating platforms, movable to allow for different orbital inclinations (extra infrastructure costs). In addition, landed stages

must be returned to launch site, either by boat (more infrastructure) or flyback (faster turnaround, but more wear on vehicle and fuel must still be transported

to landing platforms).

- movement of platform due to wave action makes landing more difficult.

Downrange parafoil landing:

+ low dV requirements without saltwater exposure.

- requires one or more floating platforms, movable to allow for different orbital inclinations (extra infrastructure costs). In addition, landed stages

must be returned to launch site, either by boat (more infrastructure) or flyback (faster turnaround, but more wear on vehicle and fuel must still be transported

to landing platforms).

+ parafoils provide cross-range capability with no fuel use.

Landing occurs horizontally, with low vertical speed but high horizontal speed. Deployable skids or wheels would allow runway landing.

- parafoils, steering system, landing gear very heavy & add complexity.

- difficult to make parafoils redundant.

- movement of platform due to wave action makes landing more difficult.

Orbital reentry to propulsive landing (2nd stage):

- if vehicle reenters nose first, must turn around prior to landing burn (requires either tiny parachute or more powerful RCS system).

- if vehicle reenters tail first, heat shield must be retracted or jettisoned to allow landing gear deployment.

Orbital reentry to parafoil landing (2nd stage):

+ parafoils provide cross-range capability with no fuel use.

Landing occurs horizontally, with low vertical speed but high horizontal speed. Deployable skids or wheels would allow runway landing.

- parafoils, steering system, landing gear very heavy & add complexity.

- difficult to make parafoils redundant.

My question is: which of these methods would end up being most cost-effective and efficient? It seems like parachutes are pretty much out, and the central core of something like a Falcon Heavy would have to land downrange, but I'm unsure whether parafoils would be worth the dV savings and possible cross-range capability.

For that matter, would a three-stage vehicle be viable? (first stage pops up, lands at launch site, second stage lands far enough down range to cross an ocean, third stage reaches orbit).

[bsalis]

Are you sure all options are viable.

With RSS, the distances and dV you are dealing with are larger. Anything further then 2.3 Km will despawn in the atmo below a certain altitude.

[Rus-Evo]

Yeah I was wondering how you steer stages 1 & 2 home whilst controlling stages 3 upwards!

What happens if you let an item out of physics range parachute down?

EDIT: Doesnt the real-life Falcon have shock absorbing landing legs? If you used the landing legs from the game you just need a Kerbal engineer to fix the ones that break. Its all extra weight, but for a good cause if your other options are possible.

Edited April 10, 2014 by Rus-Evo