Are hybrid engines as reliable as liquid engines?

[Gerdih]

What are the differences in terms of reliability?
for example, they can restart safely?

Thanks

 

[Wishbone]

What do you define as hybrid engines? Most liquid-propellant rocket engines are not restartable BTW.

 

[agentgonzo]

What do you define as hybrid engines? Most liquid-propellant rocket engines are not restartable BTW.

I imagine he means a [ame="http://en.wikipedia.org/wiki/Hybrid_rocket"]rocket engine with both solid (fuel) and liquid (oxydiser) components[/ame]. Like Spaceshipone used.

---------- Post added at 13:13 ---------- Previous post was at 12:52 ----------

As some general waffles, they are considered to be reliable and combine good bits of both solid and liquid fuelled rockets. That is, they have the advantage of liquid fuelled rockets in that they can be turned off where (most of) solid fuelled rockets can't be turned off until they burn out. They have the advantage of solids over liquids in that they are simpler and less prone to explodey badness because you can't have a rupture and mixing of all the fuel in the event of a catastropically bad kaboomy incident.

Apart from that, we're still talking vague concepts here rather than specific rocket motors. Most hybrids can't be restarted as they (like solid rockets and some liquid rockets) rely on a ground/mothership igniter.

 

[tori]

tl/dr: they can be made to be restartable, but most designers choose not to (added expense, complexity, points of failure, mass)