Author Topic: Crewed Dragon V2 flight with Kestrel in trunk extension  (Read 15944 times)

Offline sevenperforce

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Re: Crewed Dragon V2 flight with Kestrel in trunk extension
« Reply #60 on: 05/19/2016 02:26 pm »
A small 3rd stage might make sense for small payloads to extremely high energy destinations, for example sending probes to the outer solar system.

For Dragon-sized payloads headed to the inner solar system, NEOs, lunar orbit, etc, it only helps if significant orbital maneuvers are necessary beyond the endurance of the existing Merlin US... and even then, it might make more sense to try to keep the Merlin alive rather than adding a stage. The F9 upper stage is really, really efficient both in mass fraction and ISP.
One difference is that the Dragon V2 has its own high-thrust engines already...so if you can install a drop tank using the existing unpressurized cargo attachments in the trunk, figure out a way to route fuel lines into the capsule, and figure out a way to improve the SuperDraco specific impulse and eliminate cosine losses, then you save four tonnes without needing to develop much of anything at all.

But yes, keeping the MVac alive for as long as possible is a good idea.

Offline CuddlyRocket

It is essentially a solution looking for a problem from SpaceX’s point of view.  This means that SpaceX is not likely to pursue any of these options at this time.

Agreed. SpaceX appears to operate in what Zubrin called Apollo-mode (have a goal, build what you need to accomplish it) rather than Shuttle-mode (create a capability and then think of ways to use it). He contends, with some justification, that the former is far more productive.

Even so, that doesn't stop interested observers, amateur or otherwise, speculating on what modifications to SpaceX equipment could be made and what could be done with that extra capability. Just as long as one doesn't get upset if SpaceX fails to take up the idea! :)

Offline DAZ

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Re: Crewed Dragon V2 flight with Kestrel in trunk extension
« Reply #62 on: 05/20/2016 05:40 pm »
It is essentially a solution looking for a problem from SpaceX’s point of view.  This means that SpaceX is not likely to pursue any of these options at this time.

Agreed. SpaceX appears to operate in what Zubrin called Apollo-mode (have a goal, build what you need to accomplish it) rather than Shuttle-mode (create a capability and then think of ways to use it). He contends, with some justification, that the former is far more productive.

Even so, that doesn't stop interested observers, amateur or otherwise, speculating on what modifications to SpaceX equipment could be made and what could be done with that extra capability. Just as long as one doesn't get upset if SpaceX fails to take up the idea! :)

I agree speculation is fun.  It is one of those things you can do by yourself but is much more fun with friends.  My comment was more a CMA as to why SpaceX is no more likely to do what I am speculating on than any other speculation.

In my experience it has been more useful and interesting to know why someone solved a problem in a given way as opposed to how they solved that problem.  I am speculating, in this case, that SpaceX instead of using their resources for a one of solution to a one of problem that they would lump those problems together so as to use those resources to produce a solution to a variety of problems simultaneously.  Instead of speculating on a possible technical solution for a possible technical problem, look at how SpaceX has solved problems in the past to speculate on how they might solve those problems in the future.

Online Jonas Bjarnoe

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Re: Crewed Dragon V2 flight with Kestrel in trunk extension
« Reply #63 on: 07/19/2016 08:02 pm »
Speaking about Kestrel, does anybody dare to venture a guess about the chamber contraction ratio for that engine? Above or below 4?

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