Results of Advanced
Cryo-Tanks Research
Project CHATT
CHATT
(Cryogenic Hypersonic Advanced Tank
Technologies)
Martin Sippel, Alexander Kopp
Space Launcher Systems Analysis (SART), DLR, 28359 Bremen, Germany
David Mattsson
Swerea SICOMP, Piteå, Sweden
Aron Lentsch
Orbspace, Austria
Craig Walton
Gas Dynamics Ltd (UK)
Presenter: Martin Sippel (project coordinator)
Overview of Presentation
Objectives of CHATT
Organization of CHATT
Research activities in CHATT
Example of major CHATT results
Conclusion
Objectives of CHATT
In future aviation and particularly in hypersonic systems, new
propellants will be used, such as liquid hydrogen, liquid methane
and possibly liquid oxygen.
In Europe (FRP7) LAPCAT, ATLLAS, and FAST20XX investigate
advanced vehicles with these fuels for passenger transport.
The question of cryogenic propellant storage inside an airliner –
although of critical importance but by far not yet mastered – has not
been addressed up to now in sufficient detail.
The need for more detailed investigations on liquid hydrogen
tanks in future airliners is not only urgent in hypersonic aviation,
but is also essential for environmental reasons in subsonic aviation.
Thus, a project like CHATT (Cryogenic Hypersonic Advanced Tank
Technologies) was strongly needed.
System driven approach
Cryogenic fuel propulsion is already operational in advanced
launcher systems (e.g. in Europe’s Ariane rocket).
However, the airliner systems will require
more complex technology than rockets: ultra
light-weight and reusable propellant tank
systems.
All advanced cryogenic tank technologies to
be investigated within CHATT are driven by
system demands of future hypersonic
passenger configurations.
All cryo-tank technologies should be
assessed by the system requirements. Two
vehicles already under study in the EU-funded
cooperative projects LAPCAT and FAST20XX
are investigated.
System driven approach
The A2 Mach 5 Civil Transport of Reaction Engines Limited
This horizontal take-off aircraft design should be capable of flying
from Brussels (Belgium) to Sydney (Australia) in 5 hours.
Pre-cooled Scimitar engine exploits the thermodynamic properties
of liquid hydrogen.
The airframe configuration is an efficient structural shape with
circular cross section hydrogen tankage and uninterrupted carrythrough wing spars.
System driven approach
Rocket-propelled SpaceLiner based on two stage RLV has been
proposed by DLR and is an interesting alternative to air-breathing
hypersonic passenger airliners.
Rocket powered RLV-concept is highly attractive because flight
durations are two to three times lower than those of even the most
advanced airbreathing systems. (Australia – Europe in 90 minutes)
orbiter stage
passenger rescue
capsule
LOX-tank
orbiter
booster stage
LOX-tank
booster
LH2-tank
booster
LH2-tank
orbiter
Organization of CHATT
CHATT is part of the European Commission’s Seventh
Framework Programme (FP7) and run on behalf of the
Commission by DLR-SART.
Eleven different partners from seven European countries
have been participating in CHATT:
Short Name
Country
Participant organization name
DLR
Germany
Deutsches Zentrum für Luft- und Raumfahrt
FOI
Sweden
Totalförsvarets Forskningsinstitut
SICOMP
Sweden
Swerea Sicomp
ULB
Belgium
Université Libre de Bruxelles
ORB
Austria
Orbspace
ELTE
Hungary
Loránd Eötvös University (ELTE) Budapest
TUD
Netherlands
Technical University Delft
ECM
Germany
Engineered Ceramic Materials GmbH
CENAERO
Belgium
Centre de Recherche en Aéronautique ASBL
GDL
UK
Gas-Dynamics Limited
ALE
Netherlands
Advanced Lightweight Engineering
Organization of CHATT / 2
Total budget is exceeding 4.2 M€ with an EU contribution
of almost 3.3 M€.
The project started in January 2012, has been running for
42 months and ended on June 30th 2015.
Balanced funding distribution in Europe:
Financial Distribution Breakdown
9%
Germany
8% 2%
30%
12%
18%
21%
Sweden
Belgium
Netherlands
UK
Austria
Hungary
Research activities in CHATT
Challenges of CFRP tanks for cryogenics
Extremely light-weight structural design of propellant tanks is
absolutely essential for any successful hypersonic passenger
transport.
NASA TM-2006-214346
Challenges of CFRP tanks for cryogenics
CFRP composites seem to be the most attractive material.
However, one of the challenges in developing cryogenic CFRP
tanks is finding solutions for problems caused by differences in
thermal expansion coefficients (CTE).
Permeation of hydrogen molecules into non-metallic materials is a
critical issue and should be avoided. (Infiltration of GH2 into X-33
tank structure was contributor to the test failure.)
Metallic liners could help but are creating new challenges:
overcome differences in CTE of the liner with respect to the
structural shell
strong impact on overall weight
Innovative solutions are required and their feasibility is to be
proven in relevant tests.
Challenges of CFRP tanks for cryogenics
Research in CHATT will increase the knowledge within Europe,
with advancement from a pure material science level to a practical
cryogenic CFRP tank demonstrator level.
The project should take the first steps towards a common
European development of future aerospace reusable lightweight
composite cryogenic CFRP tanks.
Four different subscale CFRP-tanks are planned to be designed,
manufactured (ALE, TU-Delft, Sicomp, DLR-FA), and tested under
mechanical and thermal loads.
Not only will the advantages and disadvantages of using
liner/linerless tank designs be investigated, but also issues related
to the realization of more complex geometrical tank shapes.
Related technologies for cryogenic tanks
Thermal insulation of cryogenic tanks is more demanding than in
launcher applications because typical operation times are hours
instead of minutes
Aerogels are promising, innovative materials
NASA TM-2006-214346
Aerogel / Cryogels
The aerogel is an open-celled, nanoporous, solid foam that is
composed of a continuous 3-D network and the pores of the
network are filled up by air.
The aerogel exhibits a high porosity of more than 50%.
Advantages of aerogels exist for aerospace applications:
excellent thermal and acoustic insulation thermal conductivity (in
air) is 0.03 – 0.004 W/mK. It almost blocks all the three types of heat
transfer (convection, conduction, and radiation).
Light solid material with density of 10 – 600 kg/m3
Good resistance to damage from space radiation and outgassing.
Related technologies for cryogenic tanks
Sloshing behavior and control:
sloshing of fluids within tanks can have significant impact on
flight control because the vehicle may experience a noticeable
shift in its center of gravity
anti-sloshing devices and tank design are susceptible to
reduce these effects but will come at the cost of increased mass
and production effort
system aspects will be investigated with reference
configurations
Propellant feed system:
lower densities of fluids require tanks of large sizes and hence
long feed lines and cavitation is to be avoided
innovative propellant cross-feed between the two SpaceLiner
stages will be simulated in steady and transient behavior
Related technologies for cryogenic tanks
Pressurization using advanced ceramic heat exchangers:
C/SiC ceramic matrix composites (CMC) with high silicon
content allow achieving air-tight materials with negligible
porosity, high heat conductivity and low CTE
2 basic heat exchanger concepts with such thin-walled
materials will be designed, manufactured and tested
Cabin pressurization and oxygen supply:
air-conditioning system based on similar system used in
ATLLAS I: bleed air from intake exhaust to be cooled using
cryogenic fuel, and then compressed to achieve conditions
required for the cabin air supply.
power for compressor and other cabin sources to be provided
by Rankine cycle, 15 kW prototype turbine to be manufactured
and tested
Final research results of CHATT
Aerogel / Cryogels
Two types of porous alumina system were prepared by sol-gel technique;
cryogel and aerogel at ELTE Budapest.
Nanoporous Aerogel
Pore size 10-20 nm, porosity 40-50 %; specific surface area 300-500 m2 g-1
Hierarchical (macro- and meso-)porous Cryogel
The preparation technique of aluminum oxide cryogels is a newly developed method. Using this
method, the expensive supercritical drying process can be avoided.
The cryogels possess higher porosity and total pore volume, while the aerogels have larger specific
surface area due to their nanoporous system.
Cryogel 250 000x
Aerogel 250 000x
TEM
images
Aerogel
100 000x
SEM
images
Cryogel 1000x
Aerogel / Cryogels / 2
ELTE developed a new technology to produce an insulating blanket for high temperature
application ( 1500 C). The insulating material is a fiber-reinforced composite.
The fiber-reinforced composite consists of aluminum oxide cryogel pellets connected by
aluminum oxide fibers. The SEM images represent the new composite material and for
comparison a Spaceloft insulating blanket (applicable up to  600 C) made by NASA, ASPEN.
A: SEM image of 3D composite layer of Al2O3 produced at ELTE.
B: Spaceloft insulating blanket produced by ASPEN (NASA).
CFRP tanks
Four different subscale tank concepts have been designed
and manufactured within CHATT:
Cylindrical tank with liner
by DLR
Dry wound cylindrical tank with liner by ALE
Cylindrical tank without liner
by FOI/SICOMP
Complex shape tank
by TUD
Subsequent tests of tanks have included:
leak-check,
pressurization,
multiple cryogenic fluids tanking and draining (LN2),
investigation of fluids sloshing on DLR hexapod system
with cylindrical DLR-tank using water.
CFRP tanks - Cylindrical tank with liner
Cylindrical tank with liner by DLR-Braunschweig:
length 3 m (Cylindrical length: 2.4 m)
diameter 1 m
total volume: 1.9 m³
Different design and manufacturing concepts have been
analyzed. PE-liner produced in rotation molding process.
Afterwards wet winding on the liner with low viscosity
epoxy resin.
First layer is helix glass layer with angle of 6.8°
CFRP tanks - Cylindrical tank with liner
Winding of the helix CFRP layer (left) and final CFRP hoop layer
(right):
Finished tank is finally wrapped with peel ply for removal of
excess resin and cured in autoclave:
Delivered for testing in 2014.
CFRP tanks - Dry wound tank with liner
Dry wound cylindrical tank with liner by ALE:
Technical tank design data:
Length 0.57 m
Diameter 0.29 m
Volume
33 l
Liner
PE, blow molded
Reinforcement
T700 carbon fiber, dry wound
Calculated strain at 12 bar and at LH2 temperature in half of
the fiber network:
CFRP tanks - Dry wound tank with liner
Winding of helix layer (left) and winding of hoop layer (right)
at ALE:
Demonstrator tank after winding with protection foil:
CFRP tanks - Cylindrical “tank” without liner
Linerless tank demonstrators built in Sweden are not closed
volume tanks but rather tubes with a cylindrical section and
open ends.
The linerless demonstrator tank concept is based on the
utilization of thin-ply laminates.
Manufacturing of tube demonstrator tank is performed at
Swerea SICOMP while testing is executed at FOI.
Novel spread-tow material from Swedish Oxeon company
used named TeXtreme®.
TeXtreme® used first time for wet filament winding in CHATT
2 mm thick TeXtreme® carbon/epoxy laminate with 0 % void
content:
CFRP tanks - Cylindrical “tank” without liner
Several tubes with different fibre architecture, different
laminate thickness and orientation were manufactured.
Final optimized hybrid demonstrator casing consists of 4
layers of T700 wound at ±45°and 20 layers of TeXtreme® at
±25°
Tube manufacturing with ±45°layer of T700 (left), ±25°
layer of TeXtreme ® (right):
Test set-up at FOI:
CFRP tanks - Complex shape tank with liner
Complex shape tank with liner investigated and built by TU
Delft because of potentially improved volumetric efficiency.
Simplest possible structure of a multibubble tank selected:
Planar arrangement of identical spheres with double
symmetry and bubbles radii all at the same 150 mm.
Composite overwrapped subscale tank with a hoop fiber
reinforcing the intersections and thus providing structural
support.
External UD carbon tow (roving) is applied over the tank
wall from the outside to the inside:
CFRP tanks - Complex shape tank with liner
Manufacturing challenge: fibers must be very carefully
wrapped over intersections and tube for effective load
transfer between laminate membrane and tows.
Multibubble tank integrating a hoop fiber has been
manufactured in July and later pressure tested:
POM (polyoxymethylene) liner is made in closed mold by rotation
molding and selected tank wall material is 913C carbon/epoxy.
Sloshing Simulation and Tests
Objective:
To investigate the effects of sloshing in cryogenic fuel tanks,
including the risk of failure of the CFRP structure.
Work is split into 3 sub-workpackages: experimental test
campaign; numerical simulations; sloshing model for flight
dynamics.
Heat Exchanger Design & Testing
HX-Design (ORBSpace, ECM)
Two parallel activities helped to develop the design:
Small-scale manufacturing trials;
FE thermo-mechanical stress analysis
Small scale trials with CeSIC material prepared by ECM.
Two step manufacturing process; porous 'green-body' first
machined to form narrow channels; green-body then infiltrated with
liquid silicon under vacuum with up to 1600°C.
Conclusion
The key objectives of CHATT with a total budget exceeding
4.2 M€ are to investigate different CFRP cryogenic pressure
tanks, propellant crossfeed systems, advanced thermal
insulation materials, and ceramic heat-exchangers.
Four different subscale CFRP-tanks have been designed,
manufactured and tested.
CHATT contributed to significant progress in the design of
composite tanks for cryogenic propellant applications.
Polymer liners are sensitive to cracking.
Linerless tank technology is promising and should be
further refined and introduced into complete tanks.
In future projects lessons learned of CHATT will be useful to
bring European composite tank technologies forward.
Next step in development of European composite cryotank
should focus on fully integrated tank demonstrator.