Tuesday, June 16, 2009

Constellation: Launching Science, or Leeching Science? Part 1: Heavy Lift

Recently, NASA issued an RFI (Request for Information) on using Constellation hardware for spacecraft servicing. The general types of spacecraft that would be serviced are outlined in a couple of documents, including the National Research Council's Launching Science: Science Opportunities Provided by NASA's Constellation System. I'd like to take a closer look at that document and what it says about those science opportunities. This look will focus on 3 aspects of Constellation-enabled science:

  1. Science Enabled by Heavy Lift
  2. Constellation and Technology Development
  3. Constellation and Satellite Servicing
Today's post will cover "Science Enabled by Heavy Lift".

The early sections of this document describe a number of science mission concepts that could use Constellation. In several of cases, it was found that Constellation would not help the mission, so those missions were dropped from the study. Other missions were helped somewhat, but not enough to warrent further study. The report focused on a select group of missions that have high science potential and that would be enabled or considerably enhanced by use of Constellation hardware. In most cases the Constellation hardware in question was Ares V; Ares 1 was found to have similar capabilities to existing rockets for science purposes. Two missions, "Exploration of Near Earth Objects via the Crew Exploration Vehicle" and "Dark Ages Lunar Interferometer", used other Constellation hardware, but these strike me as being more about the human exploration and lunar surface development efforts of the main Constellation effort. I'll skip those and concentrate on the majority of the report's missions, which are traditional robotic science missions enabled or enhanced by Ares V.

Here are some important quotes from the report:

"Finding: The scientific missions reviewed by the committee as appropriate for launch on an Ares V vehicle fall, with few exceptions, into the “flagship” class of missions. The preliminary cost estimates, based on mission concepts that at this time are not very detailed, indicate that the costs of many of the missions analyzed will be above $5 billion (in current dollars). The Ares V costs are not included in these estimates."

"... expensive space science programs will place a great strain on the space science budget ..."

Given the long duration and high expense of the Constellation development phase, the high expense of the subsequent lunar surface missions, and the potential for cost overruns in these big programs, it's a pretty fair assumption that space science budgets will continue to be under strain. Given the problems with some of the NASA Science missions, in particular its larger and more expensive missions like the Mars Surface Lander, James Webb Space Telescope, and others, the space science area is likely to be under additional strains from within. Unfortunately, this is not a physics case study where internal and external pressures balance harmoniously; this is a an over-full balloon run over by a steamroller.

Given these circumstances, how is the NASA Science community going to afford missions that, in current dollars, would likely cost over $5B in initial estimates, would likely have cost overruns and delays, and would also have to pay for the use of the expensive Ares V heavy lift vehicle?

When answering that, consider the current and probable future size of the NASA Science budget, the cost of the missions in question, and the fact that NASA Science is divided into separate areas with their own funding blocks: Astrophysics, Earth Science, Planetary Science, and Heliophysics.

"The committee notes that the combined effect of expensive payloads and expensive launchers would distort the balance of the space science program."

When your balance is distorted, you fall on your face. This is why the food pyramid, with numerous small missions (smallsats, suborbital missions, and the like) providing a solid foundation, a few typical medium-sized missions filling in the center, and the occasional large flagship mission over $1B pushing the envelope is a more balanced and stable shape.

"With the advent of the Ares V, the challenge for program managers will be to temper the appetites of scientists who will clearly recognize the dramatic scientific benefits enabled by the launch system. There will need to be an enforced paradigm shift where cost, rather than launch system capability, is the design limiter."

In other words, maybe we can manage science missions to be low-cost in spite of the larger mass of the missions. This sounds like wishful thinking to me. Look at what already happens with large NASA, NOAA, and DOD missions - one after another after another after another. They don't take advantage of extra mass by making the mission cost less; they cram every capability they can in every last kg. Look at the lessons of Apollo, or Titan. The committee is aware of this:

"Prior spaceflight experience demonstrates that payloads fill all available weight and volume budgets (and power and telemetry budgets as well)."

It's not likely that virtuous program managers will restrict their spacecraft to low cost use of Ares V mass capabilities by, for example, just using the mass for lots of fuel, and otherwise getting by with the instruments and capabilities of a $400M mission. There are too many other pressures - political, science, career, management, and so on. It's not impossible, but I wouldn't risk the next few decades of NASA science on the possibility that we will manage NASA Science in such a way that Ares V class science missions are cheap.

The report also relates a "Cautionary Tale" of the Voyager-Mars robotic science mission that was planned for the Saturn V as part of the Apollo Applications Program, but was cancelled.

Interestingly,

"During the course of this study, no Earth science mission concepts were proposed to the committee. A proposed NASA workshop on the Constellation System and Earth science was canceled due to lack of interest, and only the most basic ideas about using Constellation for Earth science were discussed at the Ares V Solar System Science Workshop."

I'm not against heavy lift per se, but the current NASA heavy lift plan is incredibly expensive. It's the development and operations expense, and the corresponding missed opportunities, that concern me.

If there was a legitimate market for heavy lift, it could be worth the effort to make it happen, perhaps on a more affordable and less grandiose scale than Ares V, with a scaled-up COTS-like commercially-oriented effort.

Alternately, if there was a real government need for heavy lift, it might also be worth pursuing. A cookie-cutter series of similar nationally-important satellite missions that need Ares V payload capabilities, but that don't break the bank (eg: because of shared spacecraft development costs) would make Constellation a whole lot more attractive. NOAA, DOD, and intelligence communities all have nationally-important lines of multiple similiar satellites, so this scenario isn't impossible, but it hasn't happened, and in fact these agencies seem, if anything, to be in dire need of smaller, more responsive, and more agile spacecraft and launchers.

As it stands now, heavy lift doesn't appear to be a priority. Even for ambitious missions, other approaches that use smaller launchers and capabilities like refueling and spacecraft assembly appear more useful.

Yet heavy lift is so tempting because it gets rid of the need for various new technologies, doesn't it? That's a subject for a future post in Part 2: Constellation and Technology Development.

1 comment:

gravityloss said...

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