Difference between revisions of "Catastrophic failure"

Revision as of 20:58, 14 April 2013

A Catastrophic Failure is an event that makes it impossible to finish the mission, usually either killing the crew or stranding them in space. When testing a new spaceship design catastrophic failures are unavoidable, but unexpected events can happen even on thoroughly tested designs.

Failures of Design

Staging Sequence

A very widespread cause of catastrophic failures is incorrect staging stemming from an oversight when arranging parts into stages. This can result in engines igniting prematurely and damaging the spacecraft, or stages decoupling too soon, depriving the ship of essential fuel reserves. The most destructive is having engines or boosters in the same stage as their decouplers. This will result in the engine igniting and being seperated at the same time. Radially mounted boosters can tear off parts of the ship as they accelerate and base mounted engines will start pushing the craft uncontrollably forward, or ramming and tearing it apart. A special subset of this failure is the TT18-A Stability Clamps not disengaging because they are not in the last stage. This will often just bind the ship to the ground without endangering the crew, but the loss of fuel will doom the mission before it starts. On rare occasions the clamps can tear your craft apart given a high enough TWR.

Fix

Though very frustrating, this is the simplest problem to correct. The player just has to rearrange the parts into their correct stages in the VAB. Since all the decouplers have the same icon -except for the radial ones- one has to point the mouse at them and watch which part of the ship gets highlighted. Make sure that no engines are in the same stage with their decouplers and that the decouplers on the ship and in the list are in the correct order to avoid jettisoning stages prematurely.

Breakage and Detachment

The parts of a spacecraft have a maximum tolerance threshold for staying connected. When they are put under a large enough weight or acceleration the connections can break under the stress, making your craft fall apart. It is difficult to predict in advance where these voulnerable points will be, though experienced ship designers can identify some of the more obvious ones. Sometimes though you will only spot these weak ponts when your craft breaks apart or just falls down on the launch pad without ever taking off.

Fix

Struts are your best friend in this situation. The most obvious points of brakage are usually around decouplers where two powerful stages are connected only by a decoupler ring. Multiple struts that connect the lower and upper stage around the decoupler should resolve the issue. Another problematic structure is an engine nozzle on the end of a long line of fuel tanks that are connected to each other or a center part by the uppermost fuel tank. The thrust generated can pull these columns apart and make them wave around often hitting and damaging each other. Use struts to tie the lower ends together just above the engine to stabilize the structure.

Steering

Every part has a drag and mass value, and some have lift ratings. Sometimes you want lift, mass, or drag on certain places (especially on airplanes) but in others, these three values may wreak havoc on your rocket/spaceplane if used incorrectly, either setting it into a spin or tilting it in wild directions.

Fix

Use the three Mass, Lift, and Thrust buttons (located to the left side of the parts) to see where lift, drag, and thrust are centered. In the average rocket, these should be more or less linear, with the Thrust arrow pointing straight up. In a air/spaceplane, it's a bit different-The center of mass and lift matter a bit more (though you should still see if the thrust is centered.) The lift arrow should not tilt left/right in relation to the craft, and the mass should be in the center (and preferably nearer the back.) Once you've got these down, add a S.A.S. Module and/or an Advanced S.A.S. Module module for extra stability.

Failures in Flight

Accidental Staging

Sometimes the design is not the cause of failure. The most widespread problem is likely accidental staging. The player pushes space by accident and decouples a stage when he/she doesn't want to. The most destructive of all is the decoupling of a lower stage when the engines haven't finished their burn yet. The resulting difference in acceleration between the decoupled half and the upper intact half can cause the former to ram into the latter, tearing it apart and often killing the crew.

Fix

Pressing the lock stage key combination (default Alt+L) will toggle locking the stages. The green light below the stage list will turn purple, letting you know you have locked the stages.