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Advanced Cryogenic Evolved Stage

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The Advanced Cryogenic Evolved Stage (ACES)—formerly the Advanced Common Evolved Stage—is a proposed liquid oxygen/liquid hydrogen upper stage rocket for use on the Vulcan space launch vehicle.

The design concept is from the U.S. company United Launch Alliance (ULA).[1] ACES is 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 include 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.[1]

As of 2015, ULA announced conceptual plans to transition the Vulcan rocket to the ACES second stage after approximately 2023. Vulcan will initially launch with the Centaur upper stage, beginning with its first flight no earlier than 2019.

History

Originally proposed as the Advanced Common Evolved Stage in the late 2000s, 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.[1]

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.[2]

Advanced Common Evolved Stage

The original concept for the common stage that would be evolved from Atlas and Delta rocket technology—thus "common"—was to utilize the new high-performance upper stage, if built, on both Atlas V and Delta IV/Delta IV Heavy launch vehicles.

As originally proposed, 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.[1]

As of 2009, the upper-stage versions of ACES were proposed to be powered by enhanced RL10 engines produced by Pratt & Whitney Rocketdyne (which later became Aerojet Rocketdyne in 2013).[3]

The modular design of ACES supported the production of a number of standard propellant load stages, in a number of standard lengths, that are otherwise common, including the main propellant tank diameter of 5 metres (16 ft), "a size not seen since the 1970s." Several variants were proposed by ULA in 2010:[1]

  • ACES 41 upper stage — 41 tonnes (90,000 lb) propellant capacity
  • ACES 73 upper stage — 73 tonnes (161,000 lb) propellant capacity
  • ACES 41 tanker — no engine(s)
  • ACES 73 tanker — no engine(s)
  • ACES 121 depot — consists of an ACES 41 upper stage main vehicle (for LO2 storage) and an ACES 73 tank (modified for LH2 storage) with 121 tonnes (267,000 lb) of long-term, in-space, propellant depot capacity

Advanced Cryogenic Evolved Stage

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,[2] but currently planned for 2024-25.[4] 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,[5][6] and keeping the propellant tanks autogenously pressurized, eliminating the need for hydrazine fuel and liquid helium.[2]

As of April 2015, the internal combustion engine to be used to power the IVF system on ACES will be produced by Roush Racing.[2]

Design

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."[1]

With the addition of a solar power system, the vehicle can remain in space and operate indefinitely.[1]

Space debris cleanup

One explicit objective of the ACES design from the beginning, as part of the depot-based space architecture, has been to utilize the longer-stage endurance and the greater fuel capacity with in-space refueling capability to retrieve derelict objects for near-space clean up and deorbit. More specifically, it is an explicitly stated goal that the technical potential for derelict capture/deorbit will be enabled to provide the large delta-V (change in velocity) required to deorbit even heavy objects from geosynchronous orbits. These new approaches offer the technical prospect of markedly reducing the costs of beyond-LEO object capture and deorbit with the implementation of a one-up/one-down launch license regime to Earth orbits.[7]

See also

References

  1. ^ a b c d e f g Zegler, Frank; Bernard Kutter (2010-09-02). "Evolving to a Depot-Based Space Transportation Architecture" (PDF). AIAA SPACE 2010 Conference & Exposition. AIAA. Retrieved 2011-01-25. ACES design conceptualization has been underway at ULA for many years. It leverages design features of both the Centaur and Delta Cryogenic Second Stage (DCSS) upper stages and intends to supplement and perhaps replace these stages in the future. The baseline ACES will contain twice the Centaur or 4m DCSS propellant load, providing a significant performance boost compared to our existing upper stages. The baseline 41-mT propellant load is contained in a 5m diameter, common bulkhead stage that is about the same length as ULA's existing upper stages. ACES will become the foundation for a modular system of stages to meet the launch requirements of a wide variety of users. A common variant is a stretched version containing 73t of propellant.
  2. ^ a b c d Gruss, Mike (2015-04-13). "ULA's Vulcan Rocket To be Rolled out in Stages". SpaceNews. Retrieved 2015-04-18.
  3. ^ Kutter, Bernard F.; Frank Zegler; Jon Barr; Tim Bulk; Brian Pitchford (2009). "Robust Lunar Exploration Using an Efficient Lunar Lander Derived from Existing Upper Stages" (PDF). AIAA.
  4. ^ https://twitter.com/torybruno/status/625994038697676800
  5. ^ Ray, Justin (14 April 2015). "ULA chief explains reusability and innovation of new rocket". Spaceflight Now. Retrieved 2015-04-18.
  6. ^ Boyle, Alan (2015-04-13). "United Launch Alliance Boldly Names Its Next Rocket: Vulcan!". NBC. Retrieved 2015-04-18.
  7. ^ Zegler, Frank; Bernard Kutter (2010-09-02). "Evolving to a Depot-Based Space Transportation Architecture" (PDF). AIAA SPACE 2010 Conference & Exposition. AIAA. pp. 13–14. Retrieved 2011-01-25. for disposing of these obsolete or derelict spacecraft all [approaches] involve the expenditure of substantially more delta V than what has been traditional. It may well be required that old spacecraft be removed at the same time new spacecraft are being emplaced. ... [this architecture] anticipates the task of removing derelict spacecraft by providing an infrastructure to permit these high ΔV missions and enables the likely new paradigm of removing a spacecraft for each one deployed.
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