Thoughts On The Number Six

Over at Rockets and Such.

So, it goes from Ares 5 to Ares 6, and it still doesn't satisfy the mission requirement. And now it has outgrown the MLP.

There's a concept in the development of a space vehicle known as "chasing your tail," in which the need to add something to the vehicle (like adequate structural strength, with margin) results in more weight, which results in the need for bigger or more engines to push it, which results in the need for more propellant capacity to accelerate the added mass, which results in...

And the design won't close.

Now in fact, it is probably possible to get this design to close--bigger vehicles are easier in that regard than small ones. But regardless of the size of the vehicle, mission needs are always going to grow (and they still don't really have solid numbers on the EDS/Altair/cargo requirements). So it won't be able to get the mission concept (one and a half launch) to close, particularly as we move beyond the moon, even if it can be done for the moon.

The rationale for the heavy lifter has always been to avoid the complication of orbital assembly (apparently, the false lesson learned from our success with assembling ISS is that we should throw away all that experience, and take an entirely different approach for VSE). But it's already a "launch and half" mission, needing both Ares 1 and Ares 56, so they're not even avoiding it--they're only minimizing it. And even if the lunar mission doesn't outgrow the Ares 6, it won't be able to do a Mars mission in a single launch. So if we need to learn to do orbital assembly (and long-term propellant storage) anyway, why postpone it? Why not take the savings from not developing an unneeded heavy lifter (and new crew launch vehicle), and invest it in orbital infrastructure, tools and technology to provide a flexible system that can be serviced by a range of launch vehicles, without the single-point failure of Ares? These are the kinds of issues that a new administrator will have to consider next year.

And don't get me started on the Ares 1 problems:

The currently favored mitigation approaches - still undergoing a trade study - for thrust oscillation will add around 500 lbs to Orion for shock mounting on the crew seats and vital components.

So, because the geniuses behind this concept decided to put the crew on top of the world's biggest organ pipe, they'll add a quarter of a ton to an already-overweight vehicle with no margin, so that the astronauts will (might?) be able to survive watching the rest of the capsule being vibrated even more intensely around them.

There is a word for this. It starts with a "k" and ends with "ludge." And then there's this.

Thrust oscillation is now categorized as a 5x4 risk for the upper stage.

I'm not sure which axis is which in that formulation, but it either means that there is a very high likelihood of a catastrophic outcome, or that that it is probable that there will be a near-catastrophic outcome. And no mitigation has yet been found.

They really need to consider going from one and a half launches to (at least) two launches of a single medium-sized vehicle type. Two launches is two launches, it would save them a huge amount of development costs, provide much better economies of scale in operation and production, and get completely around the "stick" idea, which is proving to be a programmatic disaster waiting to happen, if it hasn't already. Let us finally end the cargo cult of Apollo, and develop real infrastructure.

[Late morning update]

Here's more discussion over at NASA Space Flight.

[Update a few minutes later]

In a post from a week ago, Chair Force Engineer has some related thoughts as well, on the wisdom of choosing solids at all:

The solid-liquid trade study is one that couldn't have been adequately analyzed during the 60 days of the ESAS study, and will likely end up as an interesting footnote in the Ares story. The question is whether the Ares story will fall into the genre of historical nonfiction, or fantasy and tragedy. If the latter is true, perhaps liquids were the answer after all. But the decision to not cap the weight of Ares V (even at the expense of payload) is one that taxpayers shouldn't forget if the massive rocket, and its shiny new infrastructure, ever get off the drawing board.

It seems pretty clear (as it did at the time) that the decision to build "the Stick" was pre-ordained, and that the sixty-day study was a rationalization, not a rationale, and that none of the CE&R recommendations were seriously considered. An Administrator Steidle would no doubt want to revisit it.