Impact of frequent STS launch scrubs on selection of new architecture?

[vh5150]

Frustrating to see these recent scrubs... I realize they come with the territory and vehicle involved (and sometimes only due to poor weather).  I worry that any exploration mission requiring more than "1.5" or 2 launches in the span of a few weeks might be really difficult to accomplish given NASA's more risk averse culture of the past few decades.  I suppose the presence of the Orbiter itself is one reason for many of the launch constraints in place. 

Is this a valid point in favor of larger launch vehicles that can "throw" the mission in one (or two, max) launches?  Or is this an indictment against the complexity of combining SRBs and a hydrolox core stage?  Would a kerolox core stage (without SRBs) improve the odds of launching on time? 

I'm very much a novice in all of this and realize there are many issues and questions I've stirred-up, but just wondering if this should be an important consideration in the choice of the next generation launch vehicle(s)?  Is this a really minor point in the grand scheme? 

[tamarack]

I share your concerns with multiple-launch scenarios. Any mission requiring several closely-timed launches is infeasible due to Murphy's Law. Ideally, we'll develop a HLV to loft all the hardware and follow it with an Orion launch, but the trend seems to be towards multiple-launch for fuel + multiple launch for hardware + then an Orion launch.

This approach could easily put mission parts in space for over a year waiting for completion, creating even more possible problems. A 1-2 or 1-combined (crew+mission like STS) launch is the only practical and safe way to pursue missions. I am doubtful multiple-small launch missions conceived under 'Deep Space' will ever come to fruition and we'll be stuck with 1-2 launches (cargo-manned) to ISS/LEO until a HLV is developed.

$0.02

[Jim]

Or is this an indictment against the complexity of combining SRBs and a hydrolox core stage?  Would a kerolox core stage (without SRBs) improve the odds of launching on time? 

No, the SRB's seldom cause a launch scrub

[edkyle99]

Frustrating to see these recent scrubs... I realize they come with the territory and vehicle involved (and sometimes only due to poor weather).  I worry that any exploration mission requiring more than "1.5" or 2 launches in the span of a few weeks might be really difficult to accomplish given NASA's more risk averse culture of the past few decades.  I suppose the presence of the Orbiter itself is one reason for many of the launch constraints in place. 

Is this a valid point in favor of larger launch vehicles that can "throw" the mission in one (or two, max) launches?  Or is this an indictment against the complexity of combining SRBs and a hydrolox core stage?  Would a kerolox core stage (without SRBs) improve the odds of launching on time? 

Any mission plan is going to have to take scrubs into account.  There has to be enough on-orbit loiter time to account for scrubs.  There is plenty of data for the STS history.  Each launch takes a certain number of days of hits, on average, etc.  And the launches do eventually happen!

Use of smaller launch vehicles would actually mitigate this problem in a way, since a LEO propellant depot would have to be able to store cryos for an extended time by default.  A depot design would isolate the mission from launch delays to some extent.

 - Ed Kyle