Delta III and IV
On 10 May 1995, McDonnell Douglas announced plans to develop the Delta III, a next generation expendable launch vehicle. [(1)] Building on the success of the Delta II, McDonnell Douglas plans to develop this new intermediate-class rocket with its own funds. The Delta III will be designed and developed at the McDonnell Douglas Aerospace (MDA) facilities in Huntington Beach, CA. The final assembly of the Delta III will take place in Pueblo, CO, with final checkout and launch at Cape Canaveral Air Station, FL.
The payload capacity of the new Delta III will be 8,400 pounds to geosynchronous transfer orbit, more than double the capability of the existing Delta II. The new intermediate-lift rocket will be capable of launching Hughes' largest satellite model, the three-ton, body-stabilized HS 601.
The initial customer for Delta III is Hughes Space and Communications International, a unit of Hughes Electronics Corp., which is owned by General Motors Corp. Hughes and McDonnell Douglas signed a contract for 10 firm launches, plus options for additional launches through 2005. The total value of the contract, depending on options exercised, could be up to $1.5 billion. With an anticipated first launch during the first half of 1998, and the tenth satellite in 2002, options could extend the launches to 2005.
The Delta 3 was a financial and public-relations disaster. On its maiden flight in 1998, the rocket had to be destroyed soon after launch when it strayed off course. On the next flight, the second stage didn't work properly; an expensive satellite was left in a useless orbit. The third [and as of late 2002 the last], Delta 3 carried a dummy payload. No paying customer trusted the rocket enough to risk a real satellite.
The most significant changes in Delta III's evolution from the existing Delta II are a new single-engine, cryogenically propelled upper stage and a larger fairing to house the payload. The cost to McDAC to do the upgrade is estimated at "more than $200 million." [(2)]
Major changes to the system include:
New cryogenic upper stage, with a number of details still uncertain, although the company claims to have a detailed design in hand. The engine has yet to be identified, with the company suggesting candidate engines from Aerojet, Rocketdyne and Pratt & Whitney. The current betting suggests the Centaur's RL-10 or derivative (which would seem to provide about the right performance). In general, this new cryogenic upper stage would seem to be the single largest area of risk in the program -- particularly in light of the fact that every other cryogenic upper stage has exhibited sognificant development problems. McDAC Program Director Rick Arvesen has acknowledged that this will be the greatest hurdle for Delta III. [(3)] Thus it may be anticipated that McDAC will take a rather conservative design approach.
Expanded 13.1 foot diameter fuel tank for the first stage (the LOX tank retains the existing 8 foot diameter). By growing the diameter of at least part of the core stage, the vehicle can accomodate more propellant, while keeping the existing length (which reduces controllability problems).
New 13.1 diameter payload shroud.
Upgraded solid motors (46" diameter versus 40", 10 % longer), with three of the nine motors featuring thrust vector control (currently none of the SRMs have TVC). The need for TVC on the solids appears driven by concerns that the existing core engine of the Delta II would not provide sufficient control authority for the new configuration. These would be provided either by Hercules or Thiokol, selected through a competitive procurement.
New avionics and software, although the details have not been enumerated in published reports. As with past Delta upgrades, the avionics system will probably be modified to match the new configuration, with control system software and hardware modified to support the new solids and vehicle configuration.
Unlike the Atlas 3 program, Boeing did not improve the Delta 3's engines for use on the Delta 4, but it does introduce a number of new features that will be used on the Delta 4. The upper stage introduced on the Delta 3 was used in an expanded form (using the same RL10B-2 engine as the previous version with larger fuel and oxidizer tanks) on the Delta 4, along with the Redundant Inertial Flight Control Assembly avionics system that debuted on the Delta 3.
By introducing a limited number of new components to the EELVs, and doing so as much as possible through transitional vehicles, Boeing attempted to increase EELV reliability while reducing their development risk. Lockheed Martin is confident, for instance, that the success of the Atlas 3 has proven 80 percent of Atlas 5's technologies. 2
References
1. C-reuters@clarinet.com (Reuters), buenneke@rand.org (Dick Buenneke), z9405597@cc.mita.keio.ac.jp (David Paul Huntsman), kingdon@cygnus.com (Jim Kingdon), larrison@ix.netcom.com (Larrison), mlindroo@news.abo.fi (Marcus Lindroos INF), alastair@firewall.ihs.com (Alastair Mayer), mark.oderman@channel1.com (Mark Oderman), "Delta-3," sci.space.policy, May 1995.
2. Wall Street Journal, 8 May 1995.
3. "Matching Delta II's Success May Be Tough for MDC's New Launcher," Space Business News, 17 May 1995, page 3
