Note: this article originally appeared in the March 2001 edition of ESA's publication "On Station". Eckart D. Graf is the X-38/CRV Project Manager at ESTEC.
The CRV will return International Space Station
(ISS) crews of up to seven astronauts safely to
Earth in the event of a medical emergency,
Station evacuation or if the Shuttle is not
available. The CRV is the operational version of
the X-38 prototype, which
is being developed
cooperatively by NASA,
ESA, DLR and 22 European
industrial firms in eight
countries.
CRV Mission Profile
Within 3 hours of departure
from the Station, the
Deorbit & Propulsion
System (DPS) thrusters are fired to initiate the
descent, and the module is jettisoned. The CRV
enters the atmosphere at an altitude of
about 120 km, travelling at 27 000 km/h.
Attitude is controlled initially with cold-gas
thrusters but, as air pressure
increases, the rudders and body flaps
take over. A drogue parachute
deploys at 8 km altitude, stabilising the
vehicle in a 1 g sustained sink rate. This is
followed by the 5-stage deployment of the
large 685 m
2
parafoil. Automatic guidance,
navigation and control (GNC) software steers
the CRV through its final descent and landing,
with a safe forward speed of less than 10 m/s.
Building on the expertise developed in the
X-38 programme, ESA and the European
industrial team are now transitioning into the
CRV programme. Europe brings a wealth of
experience in reusable manned space systems
and atmospheric reentry (see also the ARD
article in this issue) to the programme.
CRV development is in two phases: Phase-1
includes the design activities up to the Critical
Design Review; Phase-2 will include the
production of four operational CRVs, two
CRV/ISS berthing adapters, including the
International Berthing/Docking Mechanism
(IBDM), four DPSs and the provision of spares
and sustaining engineering.
With the full start of Phase-1 in 2001, the
first operational CRV is expected to be at the
Station before mid-2007. Until then, astronauts
will rely on Russian Soyuz capsules in
emergencies.
Major milestones during the early part of
Phase-1 are the System Requirements Review
after 3 months, an Intermediate Design Review
(IDR1) at 6 months, the Preliminary Design
Review at 9 months, and the Safety Review and
IDR2 at 12 months.
ESA began early Phase-1 activities in
December 1999: aerodynamics and
aerothermodynamics; qualification activities for
the Ceramic Matrix Composite (CMC) material,
for the hot structure body flaps, rudders and
nosecap Thermal Protection System (TPS);
display technique development and man-machine
interfaces; design activities for the
IBDM; and system and subsystem engineering
5
Station
as part of the integrated ESA/NASA team at the
Johnson Space Center (JSC) in Houston.
Since the programme began, Italy has
confirmed its participation and Austria has
joined as the 9th participant. Overall, countries
have increased their contributions – allowing a
larger ESA programme – and have vowed a
further increase no later than at the end of
Phase-1, in order to secure a European role
throughout CRV's operational phase, including
the provision of spares and sustaining
engineering. Following the approval of the
consolidated programme by ESA's Manned
Space Programme Board in September 2000,
the Request for Quotation was issued to
industry in early October. The Phase-1 proposal,
received in December, is being evaluated, with
a view to starting the full Phase-1 in the second
quarter of 2001, synchronised with NASA's
industrial Phase-1.
The scope of ESA's participation will go
beyond the X-38 partnership with NASA, and
will include additional subsystems or elements,
such as the foldable fins, the fin-folding
mechanisms, the trunnion retraction/extension
mechanisms, the crew seats and the hot
structure body flaps and nose TPS (provided for
X-38 by DLR's TETRA programme).
Europe's industrial team will also evolve
from the X-38 team, with MAN Technologie and
Alenia Spazio sharing the role of prime
contractor, and leading a team of 19
subcontractors in Austria, Belgium, France,
Germany, Italy, The Netherlands, Spain, Sweden
and Switzerland.
Genesis of the CRV Programme
The CRV is based on the X-38 technology
demonstration and risk-mitigation pathfinder
programme. ESA is developing 15
subsystems or elements of the
V201 X-38 spacecraft, scheduled
for launch by Space Shuttle
Columbia in September 2002. In
addition, ESA is providing the GNC
software for the parafoil phase of
the V131R and V133 aerodynamic
drop-test vehicles, and for the
supporting tests using a parafoil
microlight aircraft and large drop
pallets flying the full parafoil.
The X-38 family of prototypes is
supporting a robust flight test
programme, providing the
flexibility to operate and evaluate
multiple flights with parallel rapid
turnaround of the test results.
The X-38 is an innovative
combination of a lifting body
shape (first tested as the X-24 in the late 1960s
and early 1970s) and today's latest aerospace
technology,
including CMC
hot structures for
control surfaces
and nose TPS, the
world's largest
parafoil, GPS in
combination with
an inertial
platform for
primary
navigation, and
laser-initiated pyros for deploying parachute
and parafoil, deploying the Landing Gear
System and removing the inhibits for trunnion
retraction.
X-24 flight tests resolved technical issues
critical to developing the Space Shuttle, the
first reusable space transportation system.
Today, the X-38 continues that tradition for the
next manned spacecraft.
The growing depth of X-38 design data
combined with continued flight testing is
leading to the desired level of crew safety and
reliability for the final CRV design. In addition,
zero-gravity tests using NASA's KC-135 aircraft
are helping to define CRV operational
capabilities and man-rating aspects, including
crew ingress and egress, seat design and
display techniques.
In a rapid prototyping environment and
using effective management and decision-making
processes, ESA is developing X-38
subsystems at an unprecedented low cost.
Flight-testing enabling technologies for man-rated,
reusable reentry vehicles creates the
base for European industry's significant role in
CRV development.
Most of ESA's subsystems have been delivered
for system-level integration at JSC. Recent
deliveries were the Pyrex sensor, the nose
primary structure and the first batch of TPS
blankets. The CMC leading edges and the fault-tolerant
computers with adaptive
reentry software will be accepted and shipped
to JSC in the next few months. The Landing
Gear System is ready for assembly once test
fixtures are received from NASA.
The V131R, the latest aerodynamic vehicle,
refurbished to reflect CRV's shape, was
successfully flight-tested for the first time in
November 2000; five more V131R flights are
scheduled, beginning in May. November's test
scored a number of firsts: first flight of the real
(ESA-designed) vehicle shape; first flight of the
full parafoil; first flight controlled by ESA's GNC
for the parafoil phase.
The V201 spacecraft will be powered up in
March at JSC, followed by the modal survey
test in July and the acoustic test in September.
Shipping to the Kennedy Space Center is
scheduled for April 2002.
The Future
While the X-38 has been
designed to address the specific
needs of the CRV programme, it
is a flexible, robust and cost-effective
testbed that will answer
a wide range of key questions
about technologies and
operations of future reusable
manned spacecraft. It helps
researchers to probe the
hypersonic transatmospheric
flight regime, and it addresses
questions fundamental to
industry's future capability for
developing operational fully or
partially reusable spacecraft.
There is a need to take a closer
look at potential future
developments beyond the CRV. A
Crew Transfer Vehicle (CTV) may
be the next logical step, eventually
complementing the Space Shuttle. A potential
evolutionary path from the X-38/CRV to a CTV
could be an initially space-based, fully
operational vehicle offering augmented on-orbit
capabilities such as rendezvous and
docking, as well as routine landing on runways.
Evolutionary development from the CRV would
be a cost-effective transition for ESA and
European industry into the next generation of
reusable manned spacecraft. A European CTV
preparatory programme should be started in
the near term to secure a key role for Europe in
future human spaceflight and exploration.
Background Information
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ESA and the CRV
Austria MAGNA: foldable fin Belgium SONACA/SABCA: aft structure, empennage
SAS/Spacbel: software independent validation,
displays & controls/Man-Machine Interface
Verhaert: trunnion mechanism, IBDMFrance AML: aerodynamics
Dassault: aerodynamics/aerothermodynamics
ONERA: aerodynamicsGermany Astrium: parafoil GNC, software independent
validation
DLR: CMC nose thermal protection,
aerodynamics/aerothermodynamics
MAN Technologie: industrial lead,
body flap assemblyItaly Aermacchi: aerodynamics
Alenia Spazio: industrial lead, nose
primary structure
CIRA: aerothermodynamics, Scirocco plasma facility
SICAMB: crew seatsNetherlands Fokker: rudders
NLR: aerodynamics Spain Sener: landing gear, IBDM Sweden FFA: aerodynamics Switzerland Contraves: fin folding mechanism
ESA's CRV Programme is linked to the ISS
Exploitation
Programme: ESA is
negotiating with
NASA the terms of an
Implementing
Arrangement (Barter
Agreement), under
which ESA will
receive NASA-provided
Station
services such as
transportation and
high data-rate
services in return for ESA's CRV participation.
CRV contributions will be deductible from the
Station's variable costs under the exploitation
programme.
ESA's Participation in the CRV ProgramX-38 Status