megahit: update on the advanced propulsion roadmap for horizon...

Nuclear and Emerging Technology for Space, February 2015

MEGAHIT: Update on the advanced propulsion roadmap for Horizon 2020

“Megawatt Highly Efficient Technologies For Space Power And Propulsion Systems For

Long-duration Exploration Missions”

A Supporting Action For H2020 EC Programme

Presented by: Tim Tinsley (NNL)

Dr. Jean-Claude Worms1, Mr Frederic Masson2, Dr. Emmanouil Detsis1, Mr. Enrico Gaia3, Dr. Frank Jansen4, Mr. Jean-Marc Ruault2, Dr. Alexander Semenkin5, Mr. Tim Tinsley6, Ms Zara Hodgson6 1: European Science Foundation, Strasbourg, France 2: Centre National d’Etudes Spatiales , Paris, France 3: Thales Alenia Space Italia, Torino, Italy 4: Deutsches Zentrum für Luft und Raumfahrt, Bremen, Germany 5: Keldysh Research Center, Moscow, Russia 6: National Nuclear Laboratory, Sellafield, UK


Project Overview MEGAHIT is funded by the European Commission, under the 7th Framework Programme for Research and Technological Development (FP7), under grant agreement n° 313096. MEGAHIT is an EC – Russia supporting action, in preparation of the Horizon 2020 programme.

The MEGAHIT Consortium is composed by 6 partners


Project Objectives The MEGAHIT proposal started in March 2013 and concluded in September 2014. Its objectives were: to construct a road-map for nuclear electric in-space propulsion activities within the EC Horizon 2020 programme

to create a European community including Russian partners around Nuclear Space Power systems

To analyse the potential collaboration opportunities at international level


Project Rationale Nuclear power is recognized as an enabling technology. Many past projects:

• Europe: ERATO, OPUS, SNPS200… • USA: Nerva, Snap, SP100, Prometheus, FSP… • Russia: Buk, Topaz,

Space nuclear propulsion remains a technology of tomorrow • Costly, • nuclear • number of missions affordable without it • Manned Mars mission still a mission of tomorrow

Today, a renewed interest ? • In Russia: currently a MW class project • Topic addressed in DiPoP & next European R&D programme • Topic addressed in NASA Space Technology roadmaps and priorities

Megawatt level technology is the long term objective and should be a driver for shorter term, lower power projects


Phase 1

High level requirements: Collect inputs from space agencies world-wide on mission-related high level requirements their interest for international cooperation on the subject.

Reference vision: The key technologies will be identified and a reference vision of what the MEGAHIT system aims at will be sketched out.

Phase 2

Phase 3

Phase 4

Technological plans: MEGAHIT approached stakeholders that can carry out the development and engaged with them through discussions on the technologies they master

Road-maps: This is the synthesis of the three previous phases, translating into consistent road-maps what has been established in terms of goals, key technologies and technological plans

Project phases


MW class NEP power and propulsion system should be a versatile vehicle capable of operating on various types of mission.

The specific mass for the power and propulsion system (excluding propellant but including thrusters) should be lower or equal to 20kg/kW, that is to say 20 tons for 1MW.

Without more detail mission analysis a 10 year of equivalent days at full power should be considered as a preliminary target. The influence of this requirement should be studied.

Radiators should be foldable

A 20 ton system plus the associated payload would not be able to fit in a current launcher shroud so two options can be then be considered: assembly in orbit thanks to robotics, or launch with an ultra heavy launcher.

Objectives


Candidate technologies for main sub-systems


Topic Areas The topics addressed by MEGAHIT cover all the areas of space nuclear electric propulsion. The technological plans will be organised within eight topics

1. Fuel and core, relating to nuclear technologies and including shielding. 2. Thermal control, addressing heat transfer and radiating devices. 3. Conversion, addressing the technologies of conversion of thermal

energy into electricity at high power level. 4. Propulsion, relating to electric thrusters technologies 5. Power management and distribution, relating to the high power

converters and distribution cables between the generator and spacecraft.

6. Structure and spacecraft arrangement, addressing the system architecture and lightweight structures.

7. Safety and regulations, addressing the nuclear safety and other regulations.

8. Communication and public awareness, addressing the necessary steps to take to successfully communicate a nuclear space project to the public.

© CNES/Antigravité/A.SZAMES, 2006


Possible reactor systems • Needs

– Compact – Lightweight – Good coupling to electrical production – Low operational demands, easy to start up & no

maintenance – Long operational life without fuel change

Therefore, Fast reactor with gas or liquid metal coolant


Nuclear core – Role, challenge, selected fuel Role in the system For 1MWe of electric power, reactor must provide 3MWth of thermal power

Challenges •High temperature level (even higher than Generation IV reactors). •Safety to guarantee, even in case of launch failure.

Fuel 3 fuel candidates UO2, UC and UN retained for reference •UO2 wide pre-existing operational experience in Europe, but at lower temp. •UC and UN denser than UO2 + better thermal conductivity, but very limited experience

High enrichment, fast spectrum, proposed as reference •At high temperature, thermal spectrum core is heavier (x2) •Probably no moderator able to sustain high temperature (ZrH limited to 1000K) •UN texts recommends highly enriched U

OPUS by CEA


Reference for conversion •Brayton cycle - Heating performed by nuclear core, expansion by a rotating turbine coupled with an alternator, cooling by a radiator. - Could be direct: cooling fluid of the reactor is directly injected into the turbine - Or indirect: heat exchanger separates the primary loop from the conversion loops that uses a gas (He-Xe). -Main identified challenge is the temperature at turbine inlet that should be as high as possible (1300K-1600K) -Efficiency is good (31% for Thot = 1600K) -A lot of experience available from aeronautics engine, synergies are possible.

• Magneto-hydrodynamic conversion :

An interesting alternative - Could become reference, depending on the

on-going maturation results. - no moving parts - Thermal gradient produces rapid movement

of ionized fluid - Passage in a magnetic field induces electrical

current.


Reference for radiator • Heat pipes radiators Can be simple heat pipe or loop heat pipe. - High temperature gradient to manage between radiator inlet/outlet - High inlet temperature = lower surface tension. Fluid to be chosen accordingly. + Reliable: no need of pumps + Already widely used in ground and space applications. + Performance very attractive (3-5 kg/m2).

Simple heat pipe – source: espci

• Droplet radiator A long term alternative + : no metallic exchange surface, lowest

mass A mist of droplet is expelled in space

then collected back


Reference for Electric propulsion

Credits GRC NASA

Credits Snecma

Credits GRC NASA

Ion Thrusters: Built in Russia, an ion thruster with power of 50 kW is possible at the existing technology level at specific impulse of 8000 s (for Kr) and higher. In Japan half power - 25 kW - ion thrusters are studied.

Hall Thrusters: Application of Hall thrusters in Russia is justified in the specific impulse range of 3000 s to 4000 s, for Ar up to 5000 s. Available technologies allows to make thrusters with power level up to dozens kW. Increasing specific impulse may have negative effect on the operation stability and lifetime of Hall thrusters.

The available systems of Snecma are based on Hall effect thrusters using Xenon. Snecma provides not only the thrusters but also fully integrated system including thrusters, tanks, PPU, filter units and fluid control subsystems.

Electric Propulsion is a solvable technological challenge.


Deployment


Possible mission scenarios Near Earth Object deflection: Depending on the mass and trajectory of the NEO, a MW class system may be required to deflect it to protect the Earth.

Image courtesy of NASA and Touchstone Pictures

Robotic Exploration: A MW class vehicle would open new exploration mission classes like sample return from Jovian moons.


Possible mission scenarios Space tugs: for the removal of ‘dead’ spacecraft or debris, orbital station assembly (lunar orbit or in L points) and general mission support.

Image courtesy of ESA and NASA

Manned Mars Missions: A manned exploration mission to Mars would require several tens of tons to be put on the surface of the planet. Multi-MW power electric propulsion offers the possibility of reducing the number of launches needed


Conclusions High Power Nuclear Electric Propulsion offers many interesting capabilities and enables diverse classes of missions. The MEGAHIT project aims at mapping the necessary technological steps towards the creation of a Megawatt level powered nuclear electric spacecraft. Contacts with experts, agencies and institutions that have experience in nuclear systems and spacecraft design has been initiated and will result in an international workshop in order to set the technology plans for such an endeavour. It would be highly relevant to design and develop a versatile vehicle capable of doing a large panel of missions needing the same class of power A lower power system can be used as a demonstrator.


DEMOCRITOS is an H2020 proposal that will investigate the necessary demonstration activities in order to mature technologies for NEP

systems.

Detailed preliminary designs of ground demonstrator : Investigate the interaction of the major subsystems (thermal, power management, propulsion, structures and conversion) between each other and with a (simulated) nuclear core providing high power, in the order of several hundred of kilowatts. The consortium aims to develop preliminary designs of all the subsystems and the required test bench of the necessary ground experiments with the purpose of maturation of the related necessary technologies.

Nuclear reactor studies to provide feedback to the simulated as well as conceptualize the concept of nuclear space reactor and outline the specifications for a Core Demonstrator, including an analysis of the regulatory and safety framework that will be necessary for such a demonstration to take place on the ground.

System architecture and robotic studies that will investigate in detail the overall design of a high power nuclear spacecraft, together with a pragmatic strategy for assembly in orbit of such a large structure coupled with a nuclear reactor. The consortium partners will provide a preliminary design of a nuclear power spacecraft and its subsystems, detailed assembly and servicing strategy in orbit as well as proposal for in space demonstration missions with the aim of maturing various necessary technologies that either do not fit within the ground demonstrator or have the opportunity to fly in synergy with other European or international initiatives.


www.megahit-eu.org

http://www.megahit-eu.org/


Contacts CNES Frédéric Masson [email protected] DLR Frank Jansen [email protected] Waldemar Bauer [email protected] ESF Emmanouil Detsis [email protected] Jean-Claude Worms [email protected] KeRC Alexander Semenkin [email protected] NNL Zara Hodgson [email protected] Tim Tinsley [email protected] TAS-I Enrico Gaia [email protected]

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megahit: update on the advanced propulsion roadmap for horizon...

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