Credit: United Launch Alliance
The innovative Next Generation Launch System will provide the U.S. most reliable, affordable, and accessible launch service.
ULA Innovation: Advanced Cryogenic Evolved Stage-ACES, Part 1
ULA Innovation: Advanced Cryogenic Evolved Stage, Part 2
Cis-lunar 2017: A Vision for a Self-Sufficient Space Economy
The current space launch market has few profitable business sectors, such as National security, scientific exploration, human spaceflight, and communications.
ULA launch national security payloads that provide critical support to the war-fighter as weather, mapping, military communications, intelligence and surveillance. Also, it provide launch NASA scientific missions to low Earth orbit, Pluto and beyond. To support NASA human spaceflight activities on the International Space Station, the Company make partnership with Boeing to launch astronauts on the CST-100 Starliner and Orbital ATK and Sierra Nevada to launch the Cygnus and DreamChaser cargo resupply spacecraft. Finally, it launch commercial communications satellites for U.S. and international customers.
A self-sufficient economy in cis-lunar space can significantly reduce transportation costs while growing the market and increasing launch rate for all Providers.
VULCAN BOOSTER'S ROADMAP
Formerly named the Next Generation Launch System (NGLS), the Vulcan booster will be available in 2019. Leveraging technologies and processes accumulated since 2002 from the Atlas V and Delta IV programs, the Vulcan will feature a couple of unique capabilities.
As engines are the most expensive element in the rocket'architecture, ULA works to develop the capacity to re-use the BE-4 of Blue Origin that will powered the Vulcan's first stage. To do it, once the first stage is spent on orbit, the engine's subsystem will separate from the stage, deploy a reentry shield and a parachute. In an specific area, an aircraft recovered it. (More details below)
Also, like say before, ULA will use the Advanced Cryogenic Evolved Stage (ACES) as an upper stage, while will dramatically increase the vehicle’s capacity to orbit in deep space.
To introduce its new transportation system, ULA will first retired the Delta IV Medium vehicles in 2018, except the Delta IV Heavy. And, like say earlier , in 2019, Vulcan will fly concurrently with the Atlas V for an undisclosed period of time.
The Delta IV Heavy and the Atlas V will be retired following successful deployment of the Vulcan-ACES combination in 2023.
ULA'S DISTRIBUTED LAUNCH CONCEPT
The concept is to launch a disposable Drop Tank within cryogenic propellant and storing it for weeks or months. Because, most of the propellant used to put payload in orbit is burned to escape the Earth' gravity, it is necessary to re-fuel the upper stage to go further in space.
ULA has overcome this problem in making the concept to transfer the propellant's Drop Tank into a cryogenic upper stage such as Centaur, the Delta Cryogenic Second Stage (DCSS), or the Advanced Cryogenic Evolved Stage (ACES).
The current larger vehicle can lift payload of only about 25 mT to LEO, 12 mT to Geostationary Transfer Orbit (GTO) or 9 mT to Earth escape. So, what happens if a mission requires more performance?
With a larger rocket on orbit, it is possible to use propulsion like nuclear thermal or solar electric to reduce the required Initial Mass in Low Earth Orbit (IMLEO). Another option is to assemble the mission on orbit, helped by many launches.
So, the cryogenic propellant is the Liquid Oxygen (LO2) and Liquid Hydrogen (LH2) launched in a disposable “Drop Tank” on the first launch. Days, weeks or months later, the second launch will be made with the payload. The long waiting time in the vacuum of space will give some challenges to the propellant, notably the Boil Off.
Also, some to all of the propellant used from the payload launchers’ upper stage is consumed to achieve the orbit-target. Once in LEO, the upper stage/payload (Centaur) have to make some orbit phasing maneuvers for its rendezvous with the Drop Tank.
Centaur, an example of Drop Tank. Credits: ULA, Cygnus Payload, and Allan Walters
In the Picture below, we see the installation of the Delta Cryogenic Second Stage (DCSS) inside the Delta IV Heavy Rocket. It will be used in EFT-1.
Orion EFT-1 re-entry and splash down.
ULA HAVE BIG PLANS FOR THE MOON!
Already very prolific launcher of payloads in space with its Atlas and Delta families, United Launch Alliance (ULA) wants the Moon more accessible for every one. It will be not easy, but very, very possible because its determination and skills are there.
The cis-lunar econosphere is a territory that includes trade routes of business between LEO and GEO orbits, Lunar orbit, Earth/Moon Lagrange Points, and near Earth objects (NEO). These routes permit water and raw material mining, propellant refining and storage, and in-space manufacturing.
Transfer vehicles traveling along these routes will be self-sufficient because of a near endless supply of liquid oxygen (LO2) and liquid hydrogen (LH2) propellants, mined and refined from water on the Moon and asteroids.
The Lunar Poles are the perfect locations to extract resources because the moon’s rotation axis is nearly perpendicular to the ecliptic, providing almost 100% of sunlight on some regions while others are in a permanent shadow.
Transporting goods and people from the Moon to the Geosynchronous-Earth Orbit (GEO) takes less than 10% of the propellant needed for their transport from the Earth's gravity to the Orbit.
One big advantage to extracting resources where the sunlight is always present is that it gives an unlimited solar power energy and eliminates the 14-day night of equatorial. This is very interesting because, just next to it, in the permanently shadowed regions, an estimated 10 billion tons of water-ice per polehas been confirmed.
View of aLunar Crater
HOW DOES ULA WANT TO PROCEED?
To make cis-lunar economy self-sufficient, the cost of transportation needs to be reduced drastically. And, the way to lowering that cost, is through the use of space resources.
Cis-lunar econosphere. Credit: ULA
The major reason for the high cost of travelling is the large amount of fuel required to escape the Earth's gravity to reach the LEO. Once there, much less fuel is necessary to go anywhere in cis-lunar space.
Until today, the market for satellites is provided by many transportation systems using variations of multi-stage chemical rockets. All are actually expendable, although several companies are experimenting with various forms of partial or full re-usability, as SpaceX does.
Example of Energy (Propellant mass) used by each stage of an Atlas V. Credit: FAA Office of Commercial Space Transportation
As we see in the diagram, once in orbit, the energy levels to be managed are much reduced and there are no aerodynamic forces to contend with. At that point, the challenges are getting the system elements into cis-lunar space, the re-usability of stage, finding fuel, the thermal environment and the time of the mission.
Water can be easily electrolyzed into hydrogen and oxygen using solar power which can then be used for rocket propellant. Hence, it makes sense to base the cis-lunar transportation system on liquid hydrogen (LH2) and liquid oxygen (LO2), the constituents of water and the highest energy chemical propellant known.
United Launch Alliance (ULA) has most of the world’s experience operating LO2/LH2 propulsion systems in space with more than 100 rockets'launches. Its second stage of Atlas V (REF 1) and Delta IV launch systems utilize LO2/LH2 as propellant. Furthermore, the functionality of these stages is largely what is needed for the cis-lunar transportation system.
THE EVOLUTION OF THE FAMILY
The development of the Vulcan booster, the Advanced Cryogenic Evolved Stage (ACES), and theSMART Re-use concept enhances the current capabilities towards a single launch system.
With the next generation in avionics and the advancements in Guidance, Navigation & Control (GN&C) systems, ULA has a new and more capable concept of launch service.
ULA is presently working on the Booster Stage Vulcan that will increase its capacity in numerous space launch markets, such as National security, scientific exploration, human spaceflight, and communications. Also, with its goal to have a competitive All-American Engine, the company has tested the methane-fueled BE-4 of Blue Origin (REF 5) and, the kerosene-fueled AR-1 of Aerojet Rocketdyne (REF 6).
For now, ULA's prime candidate to replace the Russian RD-180 Engine (REF 4) is the high-performance, oxygen-rich staged combustion BE-4 engine because it can provide a combined thrust of about 5 million N (1.1 million lbf) to the booster.
Concept of Vulcan 561
ULA will add up to six Solid Rocket Boosters (SRBs) to the main Vulcan's booster. These SRBs, developed by Orbital ATK, will give the impulse needed for the heavy payloads, or for cis-lunar missions.
ULA has strategic partnerships with Blue Origin and Orbital ATK to improve efficiency and performance at lower costs.
STEP BY STEP
With the goal of having only one launcher by 2023, ULA is introducing its innovative technologies gradually to improve them before their finale implementation.
For now, the Vulcan will be matched to the Centaur second stage in 2019, either to the 4 or 5 m payload fairings, and launched to test its capabilities. During these tests, the total impulse of the 4 and 5 m fairings will be increased with up to four and five SRBs respectively, that will surely exceeds the power of the Atlas V's rocket.
When the main Vulcan booster is available as Provider, ULA will have a family of three launchers with its Atlas and Delta.
During the transition to eliminate Atlas, the work will continue to provide a common flight software, avionics, simulation suite, and processes.
Before the switch of the Centaur second stage with the powerful Advanced Cryogenic Evolved Stage (ACES) in 2023, Atlas will continue to fly until the couple Vulcan-Centaur is certified for missions to the U.S. government.
When the finale implementation will be done with the Vulcan booster and the second stage ACES, the prolific Delta IV Heavy will be retired. A this time, ULA will have a single and definitively more affordable launch system.
WHAT IS THE NEW UPPER STAGE ACES?
The Advanced Cryogenic Evolved Stage (REF 6) is a 5.4 m diameter second stage of about 15 meters long. It utilizes almost 68 tons of LO2/LH2 propellants and has a propellant to dry mass fraction of 0.92, while exceed the mass fraction of Centaur, the upper stage of the Atlas.
Current cryogenic upper stages Delta IV Cryogenic Second Stage (DCSS) or Centaur (REF 2), does only about twelve hours maximum of missions in space because they loose propellants via the Boil Off provided by the sun radiation.
At atmospheric pressure, Liquid Hydrogen (LH2) boil at -253⁰ C and Liquid Oxygen (LO2) at -183⁰ C.
With its long experience in cryogenic upper stages, ULA has overcome these critical problems by the development of technologies that can eliminate and reduce drastically the Boil Off of LO2 and LH2, respectively.
In 2015, United Launch Alliance (ULA) announced its Sensible Modular Autonomous Return Technology (SMART) re-use plan to recover the booster module of its Vulcan. The plan employs the non-propulsive atmospheric entry, descent and landing (EDL) technologies.
ULA set out to develop an approach that can show benefit to both spacecraft operators and shareholders for the expansive's costs of launching rockets. Its Sensible Modular Autonomous Return Technology (SMART) re-use concept sought to minimize the performance penalty while maximizing the dollar value of the elements returned, the booster engines.
The Hypersonic Inflatable Aerodynamic Decelerator (HIAD) technology use a flexible thermal protection system to protects the Bue Origine BE-4 Vulcan Engines for the atmospheric re-entry. At some level, a drogue and parafoil system is deployed and the HIAD system is jettisoned. The guided parafoil allows the system to steer toward a capture zone where a helicopter has been proceeding. The two vehicles converge to perform a Mid-Air Retrieval allowing delivery to a waiting ship.
ULA has been working with NASA Langley Research Center on maturing the HIAD concept for SMART Re-use and have honed on a 12 m implementation for the system. The company had also working with NASA Armstrong Flight Research Center and Airborne Systems to refine the Mid-Air Recovery (MAR) elements.
Inflatable Heat Shields Could Drop-Ship Bigger Robots
Currently, these phasing maneuvers are not possible with any upper stage. The ULA's Integrated Vehicle Fluids (IVF) has been conceived to enables these problems.
Existing cryogenic stages are limited to hours of operation because its power is provided by heavy batteries. Also, their maneuverability is limited by the available hydrazine or reaction control propellant's reserve. Finally, to maintain the pressure in the propellant's tank, the main engine burn is limited at two or three, provided by the helium's tank.
Once rendezvous, the Drop Tank and payload/upper stage fly in formation. To enabling the exchange of LH2 and LO2 propellants, a robotic arm will connect the transfer plumbing from the Drop Tank with the payloads upper stage and associated avionics.
When all of the propellants have been transferred, the two systems separate. The upper stage/payload perform one or more main engine burns to achieve the desired trajectory, like cis-lunar orbit. The disposition of the Drop Tank is done by its entry in the Earth's atmosphere or a future's re-use in orbit.
MINIMIZING THE BOIL-OFF IS CRITICAL
First, the Drop Tank orbit altitude must be sufficiently high to avoid atmospheric drag when it wait. Also, the tank need to be not too heavy. Then, it have to be constructed of thin stainless steel and its pressure stabilized like ULA's Centaur tank.
Example of an orbit transfer
For a 20 mT class propellant load (Atlas 552 launch), the Drop Tank is a simplified Centaur tank of 10 feet in diameter and 30 feet long, built on Centaur tooling.For the 30 mT propellant load (Vulcan 564A launch), the Drop Tank will be built using the 17 foot diameter Advanced Cryogenic Evolved Stage (ACES) tooling.
Example. If we launch 20 mT by Atlas Centaur and 35 mT with the Vulcan ACES, after one month of LH2 Boil Off, the usable transfer propellant will be 18.1 mT and 30.5 mT, respectively.
So, the net heating of the LH2 tank give a Boil Off under 0.1% per day or 900 kg per month for a 30 mT of propellant loaded in the Vulcan'ACES stage.
Shrouded in a 40 Multi-Layer-Insulation (MLI) blanket, the Drop Tank is separated by a common bulkhead constructed from two nested domes held apart with structural insulation. Between, a thin stainless steel tank walls, that provide a low structural heat conduction, connect the two tanks of LH2 and LO2.
The common bulkhead permit a passive transfer of about 80% of the LO2 thermal load to the hydrogen tank. The cold hydrogen is used to vapor cool the exterior of the LO2 tank to control its heating for a net zero boil-off.
Once on orbit, the Drop Tank remains attached and is placed in a slow (1⁰/sec) transverse spin. This transverse spin provides centrifugal acceleration during the multi-week LEO loiter that allows settled Cryogenic Fluid Management (CFM) of the LH2. By the past, settled CFM has been successfully used on all of the over 300 cryogenic upper stage missions flown of ULA.
By isolating elements at different temperatures, ULA minimize LH2 Boil Off and make the storage of LO2 without any boil-off in its Drop Tank. Because the LH2 tank is the coldest element (36⁰ R), it is placed at the top of the Drop Tank system stack and by its structural connection, moderate warm LO2 tank at 180⁰ R. The LO2 tank is connected to the hot (~500⁰ R) spent second stage using low conductivity struts.
THE "EVOLUTION" OF UNITED LAUNCH ALLIANCE (ULA)
Atlas to Vulcan Vehicle Evolution.
Centaur Atlas Second Stage. Credit: ULA
Multiple Stages of ULA.
Tank's stocks, Alabama, USA. Credit: ULA
For now, the Russian RD-180 Engine is used on ULA's Booster
U.S. Blue Origin BE-4 Engine will probably go under Vulcan's Booster!
Aerojet Rochetdyne AR-1 engine is also considered by ULA!
ACES can accommodate one 100-150 klb, two 50-75 klb, or four 25-35 klb engines, obviously with differences in thrust structures and feed lines resulting. ULA will choose between the Aerojet Rocketdyne RL-10, a Blue Origin BE-3 derivative, and an XCOR engine.
This study publied in July 13, 2015, by NexGen Space LLC (NexGen) was partly funded by a grant from NASA’s Emerging Space office in the Office of the Chief Technologist. The conclusions in this report are solely those of NexGen and the study team authors. LEARN MORE SOON