Delta IV is a group of five expendable launch systems in the Delta rocket family introduced in the early 2000s. Originally designed by Boeing’s Defense, Space & Security division for the Evolved Expendable Launch Vehicle (EELV) program, the Delta IV became a United Launch Alliance (ULA) product in 2006. The Delta IV was and is primarily a launch vehicle for United States Air Force military payloads, but has also been used to launch a number of U.S. government non-military payloads and a single commercial satellite.
The Delta IV originally had two main versions which allowed the family to cover a range of payload sizes and masses: the retired Medium (which had four configurations) and Heavy. As of 2019, only the Heavy remains active, with payloads that would previously fly on Medium moving to either the existing Atlas V or the forthcoming Vulcan. Retirement of the Delta IV is anticipated in 2024.
Delta IV vehicles are built in the ULA facility in Decatur, Alabama. Final assembly is completed at the launch site by ULA: at the Horizontal Integration Facility for launches from SLC-37B at Cape Canaveral and in a similar facility for launches from SLC-6 at Vandenberg Air Force Base.
“CisLunar – the space between Earth and the moon – holds vast opportunities for humans. Reliable, accessible, affordable access to space will help open economic opportunities. ULA’s ability to provide reliable, affordable access to space, which will provide critical infrastructure to supporting a space economy.”
“Originally proposed as the Advanced Cryogenic Evolved Stage by Boeing in 2006 as a concept for use as a new Delta IV second stage — and subsequently, the Advanced Common Evolved Stage by its corporate successor, United Launch Alliance by 2010 — ACES was intended to boost satellite payloads to geosynchronous orbit or, in the case of an interplanetary space probe, to or near to escape velocity. Other alternative uses included a proposal to provide in-space propellant depots in LEO or at L2 that could be used as way-stations for other rockets to stop and refuel on the way to beyond-LEO or interplanetary missions, and to provide the high-energy technical capacity for the cleanup of space debris.
The late-2000s ACES proposal by ULA also had a predecessor at Lockheed Martin, prior to the merger of Boeing and Lockheed Martin launch vehicle manufacturing and operations to form ULA in 2006. Known then as the Lockheed Martin common-stage concept, the upper stage was intended to “provide efficient, robust in-space transportation”, and take advantage of the high-mass fraction that is enabled by Centaur’s design and its common bulkhead to minimize combined LO2/LH2 boil off. A study funded by NASA led to the development of the Lockheed Martin concept known as ACES, under the original name of Advanced Cryogenic Evolved Stage as of 2006.
In April 2015, after ULA had announced the end of production of the Delta IV Medium in 2019 and the Delta IV Heavy in the mid-2020s, ULA renamed the stage the Advanced Cryogenic Evolved Stage, as ACES would in this case serve as the second stage on only a single launch vehicle, the Vulcan, beginning no earlier than 2023.
After the formation of ULA in 2006, the ACES concept became one that would provide a common stage that would be evolved from both Atlas and Delta rocket technology and could be used on both launch vehicles — thus “common”. The concept by 2010 was to utilize the new high-performance upper stage, if built, on both Atlas V and Delta IV/Delta IV Heavy launch vehicles. As further refined in a 2010 conference paper, ACES was intended to be a lower-cost, more-capable and more-flexible upper stage that would supplement, and perhaps replace, the existing ULA Centaur and Delta Cryogenic Second Stage (DCSS) upper stage vehicles.
In April 2015, ULA renamed the stage the Advanced Cryogenic Evolved Stage, and announced conceptual plans to complete development of the ACES technology for the Vulcan launch vehicle, flying no earlier than 2023, but currently planned for 2024-25. No plans to develop the stage for the Atlas V or Delta IV launch vehicle lines remain. However, just like earlier ACES concept proposals, ACES would continue to blend technical aspects of both Delta and Atlas technologies and manufacturing processes, as well as use ULA’s proprietary Integrated Vehicle Fluids (IVF) technology to significantly extend the ability of the upper stage to operate in space long term. The IVF technology utilizes a lightweight internal combustion engine to use propellant boiloff (normally wasted when boiloff gasses are vented to space) to operate the stage including production of power, maintaining stage attitude, and keeping the propellant tanks autogenously pressurized, eliminating the need for hydrazine fuel and liquid helium.
The ACES vehicle is “based on a simple modular design” where the “use of multiple barrel panels, similar to Centaur, provides a straightforward means to building multiple-length (propellant load) stages that are otherwise common. The common equipment shelf accommodates one, two, or four RL10 engines. While ACES can start with existing Centaur and Delta pneumatic, avionics and propulsion systems it is intended to transition to lower-cost and higher capability systems founded on the Integrated Vehicle Fluids (IVF) system concept. IVF eliminates all hydrazine, helium, and nearly all batteries from the vehicle. It consumes waste hydrogen and oxygen to produce power, generate settling and attitude control thrust, and autogenously pressurize the vehicle tanks. IVF is optimal for depot operations since only LH2 and LO2 need be transferred, and it extends mission lifetimes from the present dozen hours to multiple days.” With the addition of a solar power system, the vehicle can remain in space and operate indefinitely.”
“The Wideband Global SATCOM system (WGS) is a high capacity satellite communications system planned for use in partnership by the United States Department of Defense (DoD) and the Australian Department of Defence. The system is composed of the Space Segment satellites, the Terminal Segment users and the Control Segment operators.
DoD wideband satellite communication services are currently provided by a combination of the existing Defense Satellite Communications System (DSCS) and Global Broadcast Service (GBS) satellites. According to United Launch Alliance, quoted on Spaceflight Now, “A single WGS spacecraft has as much bandwidth as the entire existing DSCS constellation.”
The constellation of WGS satellites increases the communications capabilities of the militaries of the United States, Canada, and Australia by providing additional bandwidth and communications capabilities for tactical command and control, communications, and computers; intelligence, surveillance, and reconnaissance (C4ISR); battle management; and combat support information. Canada has also signed on to become a partner.
WGS also augments the current Ka-band Global Broadcast Service (on UHF F/O satellites) by providing additional information broadcast capabilities as well as providing new two-way capability on that band. The combination of the Wideband Global Satellites, DSCS satellites, GBS payloads, wideband payload and platform control assets, and earth terminals operating with them has been referred to as the Interim Wideband System (IWS). It provides services to the US DoD and Australian Department of Defence. The IWS System supports continuous 24-hour-per-day wideband satellite services to tactical users and some fixed infrastructure users. Limited protected services will be provided under conditions of stress to selected users employing terrestrial modems capable of providing protection against jamming.
The WGS satellites will complement the DSCS III Service Life Enhancement Program (SLEP) and GBS payloads and will offset the eventual decline in DSCS III capability. WGS will offer 4.875 GHz of instantaneous switchable bandwidth, thus each WGS can supply more than 10 times the capacity of a DSCS III Service Life Enhancement Program (SLEP) satellite. Once the full constellation of 6 WGS satellites is operational, they will replace the DSCS system. WGS-1 with its 2.4 Gbit/s wideband capacity, provided greater capability and bandwidth than all the DSCS satellites combined.
Operation and usage of the system is broken into 3 segments.
The end users of the communication services provided by the WGS are described by the DoD as the terminal segment. Users include the Australian Defence Force and U.S. Army ground mobile terminals, U.S. Navy ships and submarines, national command authorities for the nuclear forces, and various national security/allied national forces. Additionally, the Air Force Satellite Control Network will also use the WGS in a similar manner as the DSCS III constellation is used to route ATM packets through the DISA “cloud” to establish command and control streams with various satellite constellations. One of the emerging applications is SATCOM-ON-The-Move which is now being extensively used on the military tactical vehicles for Blue Force Tracking and C3 missions.
The satellite operators in charge of commanding and monitoring the satellite’s bus and payload systems as well as managing the network operating over the satellite are the control segment. Like the DSCS constellation that WGS will replace, spacecraft bus will be commanded by the 3rd Space Operations Squadron of Schriever AFB, Colorado. Payload commanding and network control will be handled by the Army 53rd Signal Battalion headquartered at nearby Peterson AFB, Colorado with subordinate elements A Co. at Fort Detrick, Maryland, B Co. at Fort Meade, Maryland, E Co. at Fort Buckner, Okinawa Japan, C Co. Landstuhl Germany, and, D Co. Wahiawa, Hawaii.
The primary contractor for the satellites themselves is Boeing Satellite Development Center, which is building them around the Boeing 702 satellite platform. Originally five satellites were planned. On October 3, 2007, Australia’s Department of Defence announced that the country would fund a sixth satellite in the constellation. Once in their orbits at an altitude of 22,300 mi (35,900 km), each will weigh approximately 7,600 lb (3,400 kg). The program intends to use both the Delta IV and the Atlas V as launch vehicles. The Air Force Space Command estimates each satellite will cost approximately US$300 million.”
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