NASA’s decision to discontinue using the Delta 2 rocket when the relevant contractual obligations run out soon after 2010 almost certainly means the end for what has been the most reliable expendable launcher in the U.S. fleet for nearly two decades.
NASA says its choice was based on economics – that in the long run, the U.S. Air Force’s Evolved Expendable Launch Vehicle (EELV) rockets, though substantially larger, will be comparable in cost if not cheaper than the Delta 2. Maybe so, but there is something about discarding a perfectly good rocket – one that has served an important military, scientific and commercial payload niche over the years – that just doesn’t sit quite right.
It is true that the Delta 2’s price tag has risen significantly in recent years and is poised to go much higher once the Air Force stops using the vehicle over the next year or so. NASA was facing the prospect of having to foot the entire bill for Delta 2 launch infrastructure and overhead – in addition to paying the high-unit costs associated with very
low production rates. On top of that, there is the substantial near-term cost, one NASA can ill afford right now, of restarting production lines for certain components unique to the Delta 2.
Given all that, plus the fact that its projected manifest of Delta 2-class missions is less than two per year from 2011 to 2020, NASA can make a reasonable case for abandoning its trusty workhorse in favor of the Delta 4 and Atlas 5, which were developed under the EELV program.
In doing so, NASA also will be providing a measure of price relief to the Air Force by boosting, albeit only slightly, EELV vehicle production rates.
But comparing favorably on cost to a malnourished Delta 2 program does not necessarily make the EELV an economically attractive solution for NASA payloads. For example, NASA is paying some $130 million to launch its Lunar Reconnaissance Orbiter mission next year aboard an Atlas 5 – a cost it would have to bear regardless of whether or not it had a secondary payload to make full use of the rocket’s capacity.
The Atlas 5 and Delta 4 are in fact overkill for the majority of science payloads that NASA launches. The numbers tell the story
: The Delta 2 is capable placing 900-2,170 kilograms of payload into geostationary transfer orbit and 2,700-6,100 kilograms into low Earth orbit. The Delta 4 is designed to loft 4,300-12,980 kilograms to geostationary transfer orbit and 9,440-22,950 kilograms to low Earth orbit. The Atlas 5 is comparable to the Delta 4 except on the high end; there is no heavy-lift version of the Atlas 5.
The gap between the low-end EELV and the Air Force’s as-yet-unproven Minotaur 4, the largest of the small rockets in the U.S. fleet, is even bigger. The Minotaur 4, based on the first stage of the Peacekeeper missile, will be capable of placing 1,750 kilograms into low Earth orbit.
It goes without saying that using EELV rockets to launch Delta 2-class payloads – or smaller ones, for that matter – is fairly uneconomical. Dual manifesting is possible, of course, but tends to be problematic, especially for NASA, whose science missions come few and far between and often require specialized orbits and have narrow launch windows.
One can make the point that NASA satellite designs are driven by Delta 2’s capacity limits and that
scientists would adapt to its demise by building payloads to match the EELV’s capability. It stands to reason
that such payloads would be more capable than Delta 2-class spacecraft. But there is another side to that coin: The Delta 2’s constraints impose a discipline that counters a natural but costly tendency of scientists to hang more and bigger instruments on their satellites. NASA will be hard pressed for the foreseeable future to build many science satellites big enough to require the full lifting capacity of an EELV.
For anyone with the audacity to believe it possible to launch 2,000-plus kilograms of payload to low Earth orbit for a lot less than $130 million, this situation presents an opportunity. At least two companies – Space Exploration Technologies Corp. () and Orbital Sciences Corp. – are working on or considering vehicles that would fill the void left by the Delta 2’s retirement. Both companies have credibility: Orbital is a well-established system integrator in this business while startup SpaceX has conducted two launches – albeit unsuccessful ones – of its Falcon 1 small rocket and is well into development of it Delta 2-class Falcon 9.
Orbital and SpaceX are well aware of
how difficult it is to develop a reliable
rocket with an affordable price tag:
the Delta 2’s cost did not skyrocket because its manufacturer, , is blind to potential efficiencies. The Delta 2’s reliability record, moreover,
will be a tough act for anyone to follow.
To its credit, NASA has not ruled out utilizing new medium-class launch vehicles should they become available in the future. The agency could help make this happen by adopting a better system for qualifying new rockets to carry science payloads; the current standards present a nearly insurmountable
The Air Force, for its part, also should keep an open mind toward using a new, medium-class vehicle, particularly for experimental or operationally responsive satellites. It will be difficult for anyone to make a business case for a developing such a rocket based solely on NASA’s payload manifest, and, more to its own concerns, the Air Force might find a Delta 2-type capability coming in quite handy a decade from now.