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Ariane 5 ECA Adaptation .pdf

Original filename: Ariane 5 ECA Adaptation.pdf
Title: Vulcain X technological demonstration roadmap
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66th International Astronautical Congress, Jerusalem, Israel. Copyright ©2015 by de Chambure & al. ESA released to IAF to publish in all forms


Daniel de Chambure
European Space Agency (ESA), Launcher Directorate, Paris, France,
Eric Ollivet, Pascal Noir, Norbert Lidon, Charline Dutertre
Centre National d'Etudes Spatiales (CNES), Direction des Lanceurs, Paris, France,
Eric.Ollivet@esa.int, Pascal.Noir@esa.int, Norbert.Lidon@esa.int,
Nicolas Verstappen
RHEA for European Space Agency (ESA), Launcher Directorate, Paris, France,

With the Ministerial Conference 2014 decision of implementing Ariane 6 launcher as from 2020, Ariane 5 ECA
launcher exploitation has to be maintained and continued until at least 2024. In view of the tightening of the
conditions of the market for launch services, of the overall costs of exploitation and of the evolution of the mass of
the satellites, an increase in the capacity in double launch of Ariane 5 ECA by lengthening the fairing volume and
bringing its performance larger than 10,000 kg of payload in GTO appears today as an important factor for ensuring
the competitiveness of the Ariane 5 ECA launcher till its planned end of life.
With regards to the situation, ESA had already undertaken several performance improvement plans to reach above
objective. A first performance improvement plan (with Slice 10 and Performance Improvement Plan (PIP)) initiated
in 2009 has brought the Ariane 5 ECA launcher generic performance today up to 10 300 kg (total mass of payload
including carrying structures).
A second performance improvement plan (Upper Part Adaptation - UPA) was undertaken end 2013 and should
bring the generic performance up to 10 550 kg beginning 2017 while increasing the payload available volume under
the fairing, in particular for accommodating large electrical satellites.
A third performance plan beyond 2016 which also takes into account launcher recurring price decrease aspects is
today under consideration.
In parallel, the Ariane 5 ES launcher with re-ignitable upper stage, developed and successfully used for the ATV
missions is being adapted for the deployment of the Galileo Full Operation Capability (FOC) constellation with
three planned flights which should be the last ones of the ES version. This launcher adaptation included the
development of a dispenser for carrying and separating 4 Galileo S/Cs, the redesign of the VEB structure for mass
saving purpose thanks to loads decrease compared to ATV mission and some electrical and thermal modifications of
the launcher for the long duration ballistic phase. This program initiated in 2012 was very challenging in terms of
planning with regards to the first launch foreseen now second half of 2016.
This paper will address the different performance and fairing volume improvement plans for Ariane 5 ECA and then
focus on the development and qualification of Ariane 5 ES launcher for Galileo FOC mission.


66th International Astronautical Congress, Jerusalem, Israel. Copyright ©2015 by de Chambure & al. ESA released to IAF to publish in all forms


without increase of recurring costs for the production
and the exploitation of the launcher: it was also carried
out in such a way to minimise the modification of the
definition of the launcher as well as the impacts on its
qualification. Worth mentioning is that the return
investment of these program is very beneficial when
compared to the price of the launched kg (investment
of approximately 25 MEuros for 735 kg performance
gain in GTO to be compared to an average launch
price of 15KEuros per kilo in GTO).


Performance situation in 2013-2014
Since the first Ariane 5 ECA successful flight on the
12th of February 2005, 50 Ariane 5 ECA were
successfully launched among more than 75 successful
Ariane 5 launches in total since 1997.
A generic 1 performance of 9.6 tons to GTO was
demonstrated on a first flight VA179 in 2007 with the
Ariane 5 ECA launcher in its PA2 configuration (with
welded case boosters and Vehicle Equipment Bay
(VEB) structure in CFRP) within the frame of the ESA
Slice 10 development program.

The performance improvement tracks implemented on
Ariane 5 ECA are classified as follows:

An increase of the payload loading capacity of Ariane
5 ECA in dual launch configuration for GTO missions
was implemented through two programs in 2009 and
in 2013, as it was considered to be an important factor
for improving the competitiveness of the launcher and
obtaining a balanced exploitation of Ariane launcher.
The targeted performance was 9.5 tons of net payload
corresponding to a GTO generic performance of 10.3
tons (i.e payload mass including adaptors (above 2624
interface) and SYLDA) for an azimuth of 90 degrees.
This performance increase of 700 kg – 2009’s
performance was 9.6 tons - was especially beneficial
for the positioning of Ariane 5 ECA with regards to
payloads heavier than 6 tons.

Figure 1: Launcher performance evolution and
application rank
This generic performance increase up to 10,300 kg
was achieved by end 2014 (as shown in figure 1) and

Launcher knowledge improvement and
margin exploitation that enable reducing the
dispersions and the uncertainties used for
mission analysis by addressing experience
capitalisation based on post flight data
analysis. This axis is very interesting as it
mainly addresses functional aspects, without
impact on H/W and is hence affordable in
terms of costs and planning
Propulsion optimisation of the engines
dealing with the functional optimisation of
EPC and ESC stages (especially LH2 thermal
residual reduction for ESC-A), and more
specifically the propulsive parameters of the
Vulcain 2, HM7-B and MPS engines. This
axis is also very attractive in terms of cost
and gain as no H/W modification is needed.
Structural optimisation addressing structural
limited redesign of the launcher upper part
(especially payload carrying structures),
including redundant unit suppression. This
axis is also effective as offering a 1:1 gain
ratio. Yet the major drawback of such H/W
improvement is the planning (typically 2 to 3
years needed) as well as related development
cost and system impact
Evolution on the trajectory constraints: the
family addresses some system constraints that
can be attenuated provided safety rules and
criteria are satisfied.

Detailed description and outcome of the performance
improvement activities (Performance Improvement
Plan (PIP)) are reported in [1], [2] and [3].


Generic performance corresponds to a guaranteed
performance for an average value of parameters (including
engine performance and launcher dry masses) within a
qualified domain including dispersions and uncertainties
associated to a a success mission probability. Typically, the
different parameters are considered with ±3σ deviations, and
the success mission probability is 99%.

Evolution since 2013
In 2013, launch market analysis pinpointed that the
average GTO payload mass was expected to continue
increasing in the following years: this increase in
average mass could be broken down as a tendency of
the big satellites towards a mass range of 6.0-6.5 tons


66th International Astronautical Congress, Jerusalem, Israel. Copyright ©2015 by de Chambure & al. ESA released to IAF to publish in all forms

and the small satellites towards a mass range of up to
3.2 to 3.5 tons, associated with an increased volume
requirement for particularly the heavy satellites
positioned as upper passenger on Ariane 5. The
volume of the big satellites is dimensioning the length
of the SYLDA. Today’s standard is SYLDA +1500,
but heavy satellites already in the manifest of
Arianespace for launch in the period 2015-17 will
require a shorter SYLDA, which increases the
difficulty of finding a co-passenger that will fit within
the volume of a shortened SYLDA. This situation
might become worse with the advent of small
electrical satellites in the mass range of 2-3 tons,
which will require a relatively large volume with
respect to their weight inherent to the concept of
electrical propulsion satellites

metallic ring webs also avoiding the need of a static
In parallel, at system level, analysis have been carried
out - in a first step for the short ACY - to ensure that
the launcher was still in its qualified domain,
especially for GNC (no need of control law retuning),

Hence, it was decided to implement the Ariane 5
Upper Part Adaption plan with main objective to
provide by end 2015 the operational capability of the
Ariane 5 ECA launch system to:

perform dual launches with a big satellite in
the range 6.0 - 6.5 tons and a small satellite
of up to 3.2 - 3.5 tons,
increase the payload compartment volume to
allow the accommodation of larger volume
satellites in the upper and lower positions,
maintain the current mass performance of
Ariane 5 ECA in terms of injection to GTO

Figure 2 :A5 ECA fairing volume increase with
implementation of ACY (left) compared to
current configuration (right)
A number of launcher performance increase solutions,
or more precisely a number of ‘tracks’ potentially
leading to a performance gain, have been identified
during the past years within the different performance
improvement studies, for further implementation
and/or investigation depending on their (technicalcost) feasibility.

While several possibilities exist to increase the volume
for both upper and lower positions, a solution based on
a Raising Cylinder has been identified as the optimum
in terms of development time and recurring costs
impact. The Raising Cylinder called ACY added on
top of the ESC-A stage and combined with a shorter
SYLDA (see figure 2), increases the total volume of
up to 2 m (+0.6 m for lower payload and up to 1.4 m
for the upper payload). The existing 5400 mm
diameter ACY coming from earlier Ariane
developments with different heights ranging from 0.5
m to 2 m was qualified for a medium fairing
configuration only.

At the end, the following tracks in table 1 (with their
potential performance gain) compatible with an
operational application in the period 2015-16 were
Improvement tracks
Return of Experience (incl.
reduction of HM7B LOX
Chill Down duration)
Vulcain 2 mass flow increase
by 3% incl. ribs removal on
HM7B nozzle temperature
(TPDIV) uncertainties
Introduction of Optimisation
de l’Utilisation de la Réserve
Statistique (OURS) at 90%
Not generic

The introduction of the Raising Cylinder has the
drawback in terms of in-orbit mass performance as the
ACY structure remains on the ESC stage into injection
orbit. This performance penalty is between 150 kg and
250 kg depending upon the exact upper part
configuration (ACY + SYLDA).
For Ariane 5, at product level it was checked that the
old ACY definition could withstand the loads (long
fairing 17 m + internal branch): this verification led to
a slight redesign (thickening) of the lower and upper

gain (kg)



End 2015




End 2016


End 2015

Table 1: UPA performance improvement tracks


66th International Astronautical Congress, Jerusalem, Israel. Copyright ©2015 by de Chambure & al. ESA released to IAF to publish in all forms

These additional generic performance improvements
indicate a total potential gain of 250 kg (w.r.t. the
2014’s performance of 10.3 tons (not taking into
account ACY impact) which should bring the launcher
generic performance above 10.5 tons by end 2016 as
shown in figure 1. Above figures do not take into
account OURS performance track which is only
available for specific missions.

existing design margins. With today’s analysis, at
post-PDR level, minor impacts are expected on engine
including all its sub-systems: the only noticeable
evolutions concern the combustion chamber pressure
and the flow rate and pressure at the entry of the
hydrogen TPH.
The qualification of this Vulcain 2 improvement will
be in particular demonstrated by engine firing tests (in
total 11 tests on one engine but using two different
TPHs for a total endurance duration of 7500 seconds)
on complement of the Vulcain-2 ARTA 10 campaign,
currently on-going.

Each of the above UPA activities are described below:
Continuation of return of Experience (REX)
REX activities already engaged in previous
performance plans will be pursued with emphasis on
propellant reserves, propulsive parameters, tank filling
conditions and ESCA engine chill-down.

In synergy with the latter activity, the removal of the
ribs on the Vulcain 2 engine nozzle will be
implemented, allowing re-centering of the perturbing
roll moment during the EPC flight. This design has
already been tested and validated at engine level at the
occasion of the last two ARTA test campaigns in 2010
and 2012. In a first step, the expected performance
gain shall be in the range 20 kg, resulting from a slight
0.1sec Isp increase. In a second step, further to the
evaluation of the 5 first flights with nozzle ribs
removed, an additional performance gain is expected,
resulting from both a refined Isp increase and a
reduced LH2 consumption by the roll control system
(SCR). This could reach about 50 to 60 kg.

Propellant reserve reduction: Propellant reserves are
computed based on mathematical dispersion model of
the launcher propulsion systems so as to take into
account the scattering of the propulsion between
flights, as well as of the filling conditions. Flight REX
shows that these computed reserves are far from being
totally used, especially on the EPC stage and could be
reduced to increase payload mass.
The propellants’ reserves will be improved by
reducing, based on flight REX, the dispersions that are
used to compute these reserves, i.e. :
• The dispersions of EPC/Vulcain 2 &
ESCA/HM7B propulsive parameters,
• The dispersions of EPC & ESCA tanks’
filling parameters (including loading pressure
and level).

HM7B nozzle temperature
uncertainties reduction



The decrease of uncertainties on HM7B Nozzle
Extension (NE) temperature (TPDIV) consists in
reducing the uncertainties on the predicted NE flight
temperature in order to increase the maximum
reachable NE flight temperature i.e. the LH2
consumption and thus increasing the allowable LOX
loading up to the maximal tank capability (12 302 kg)
on the whole mixture ratio range. No modification of
the NE temperature qualified level is foreseen. This
track should allow a gain of about 30 kg in average
depending upon engine mixture ratio. This temperature
uncertainty reduction will be achieved by measuring
and analysing the evolution of the HM7B NE
temperature mapping during three A5 ECA flights to
be specifically instrumented.

Expected performance gain, resulting from the overall
reduction of propellants’ reserves is about 120 kg in
ESC chill-down: The objective is to reduce the LOx
chill down duration of ESCA stage during EPC flight
phase in order to save propellant for performance
increase. The expected performance gain is around 10
kg in GTO.
Vulcain 2 mass flow increase by 3% associated with
ribs removal on Vulcain 2 nozzle
The increase of the Vulcain 2 engine thrust will be
achieved by increasing the total engine mass flow rate
by 3 % without hardware and engine mixture ratio
modification, beyond the qualified reference for a
launcher performance increase estimated to be about
110 kg. The 3 % increase was found to be the best
compromise between the launcher performance gain
and the impact on engine side, taking into account past
flight and testing campaign experience as well as

Optimisation de l’Utilisation de la Réserve Statistique
Another performance gain will be achieved on a case
by case basis by the use of so-called OURS procedure
consisting in the optimization (i.e. reduction) of the
performance reserve, for maximizing LOx usable
mass. The objective of OURS for Ariane 5 ECA is to
extend the launcher qualification for a LOx tank


66th International Astronautical Congress, Jerusalem, Israel. Copyright ©2015 by de Chambure & al. ESA released to IAF to publish in all forms

depletion probability up to 10% based on existing
Ariane 5 qualification, also supported by Ariane 4
flight experience (four flights using OURS, procedure,
with up to 50% depletion probability, one of which
leading to actual LOX depletion). OURS procedure
should bring an additional performance of up to 110
kg for A5 ECA in GTO.

needed for properly justifying the applicability of the
current algorithm of the Thrust Tail Off detection of
the ESC-A stage (in case of LOx depletion).
UPA investments (ACY and performance including
costly engine testing) amounts to appr. 45 MEuros for
400 kg performance gain which, compared to previous
PIP figures (25 MEuros for 730 kg) illustrated well the
increasing difficulties for gaining performance.

In order to be able to use OURS procedure, the
following issues have to be tackled:

Prospective beyond 2016

innocuousness of the ESC stage to specific
ESC engine chugging profile for a shut-down
at LOx depletion
confirmation by computations of engineering
assessment related to the impact of lower
acceleration on void fraction profile and of
the applicability of current thrust tail-off
profile for system studies (in particular for the
validation of thrust tail-off detection

Today’s prospective for the transition Ariane 5 ECA to
Ariane 6 shows that Ariane dual launch concept will
be continuously and more and more challenged
simultaneously by both satellites evolution and recent
success of emerging low cost competitors, hence
increasing pressure on costs, performance and
flexibility. Easily reachable performance tracks with
advantageous Return of Investment (RoI) have already
been selected and developed. Hence, for further gains,
more drastic solutions in terms of technical and
investment have to be identified and implemented with
likely a longer development duration requesting
anticipation by today if these tracks need to be
available as from 2017.

In a first step, some dynamic computations have been
initiated to verify the impact of specific HM7B
chugging excitation profile (for the case of engine
shutdown upon complete LOx depletion) on ESC
equipment. A preliminary diagnosis revealed that this
new chugging profile resulted in the exceeding of
qualification levels for about 20 equipments (mainly
valves and regulators) installed on ESCA thrust frame.

Within this context, accounting for Ariane 5 ME and
Ariane 6 development studies, ESA hasanalysed some
heavier modifications leading potentially to even
Ariane 5 ECA launcher configuration evolution. As for
UPA, these modifications aim at extending the payload
compartment by 2 meters while maintaining (or
possibly increasing) the guaranteed performance, with
a first application in 2017 are listed below:

Complementary analyses were then carried out to
further assess the issue, by improving the chugging
excitation profile, by assessing the criticality of these
dynamic load exceeding, taking into account that this
is a transient phenomenon (<800 msec), and by
reanalysing old test results of an H10 stage (EP109)
subjected to a LOx depletion test, during which no
equipment degradation was noticed. The analysis
considerably reduced the number of non-qualified
equipment Finally, dynamic tests were successfully
conducted on the last few ESC stage equipments for
which no demonstration could be done by analysis, i.e.
namely one battery, the GHSM and some valves (V28
and V40) and pressure regulators (D46 and D50).

In parallel, a new draining model of the LOx tank and
LAO (Ligne d’Alimentation Oxygène i.e LOx feed
line) has been developed for computation of void
fraction evolution profile till complete depletion: the
model has been rescaled with Ariane 4 experience.
Computations for Ariane 5 ECA then confirmed that
the Ariane 5 conditions (with more than twice lower
acceleration compared to Ariane 4) lead to a smoother
vacuum profile (starting a bit earlier), hence validating
the applicability of current thrust tail-off profile for
system studies. All system studies have been
completed with exception of complementary studies

Out of Autoclave (OoA) fairing (see below)
VEB cone merging up to 1780 interface
allowing deletion of one metallic interface
ring bringing up to 90 kg of performance
ESC-A+ consisting of a limited stretching of
LH2 and LOx tanks (appr. 50 mm) allowing
an HM7-B functioning increase by about 30
sec and bringing a performance gain of about
100 kg
SYLDA Fiber Placement is a change of
manufacturing technology from CFRP
assembled elements (cones and cylindrical
panels) to fiber placement technology which
should allow decreasing its mass by about 20
kg. The mass reduction (and subsequent
performance gain) only slightly depends upon
the extent of the redesign (upper cone or
complete SYLDA).

Today, the Out of Autoclave (OoA) fairing is the more
mature track and has already been initiated. This new


66th International Astronautical Congress, Jerusalem, Israel. Copyright ©2015 by de Chambure & al. ESA released to IAF to publish in all forms

Out of Autoclave (OoA) technology should provide a
fairing mass reduction of 230 kg corresponding a
performance gain slightly above 20 kg as well as a
significantly recurring cost reduction. This new
manufacturing process has been developed by A5ME
with the possibility of a fairing elongation (up to 20m
foreseen on A5ME) to accommodate larger payload in
dual-launch configuration. This development also
enables a transition between today’s A5 ECA and A6
programmes (A6 development risk mitigation) and
should be available for first flight by end 2017.


Mission objective
The Ariane 5 ES launcher is foreseen as a second
source launcher to Soyuz for launching the Galileo
FOC constellation satellites (by group of 4) into a
Medium Earth Orbit (MEO) (by direct injection) with
a specified performance and injection precision.
The reference MEO orbit (also called “ graveyard
orbit”) is defined as follows:
• Semi-major axis (a) : 29 300 km with a
precision of ± 100 km (at 3σ)
• Eccentricity (e): 0 with precision <10-3 (at 3σ)
• Inclination (i) : 54° - 58° (continuous band)
with a precision of ± 0.12° (at 3σ)
• RAAN (Ω) : to be determined between 0360° with a precision of ± 0.12° (at 3σ)
• Difference (RAAN) between the three orbital
planes: 120°
• Stability better than 100 years (i.e. graveyard
orbit - where the EPS stage will be left at end
of mission - shall never cross operational
orbit with semi-major axis at 29 600 km).

The Ariane 5 ECA OoA fairing design is directly
derived from the Ariane 5 ME one whose development
was stopped at its CDR beginning 2015. The main
innovations in the OoA fairing are:


the use of new OoA curing and
manufacturing technology to eliminate
manufacturing joints,
the production in a new, process optimised
facility (under development and qualification
at Emmen (CH- RUAG facility))
the use of higher performance materials and
other technical and manufacturing cost

With the OoA technology, the fairing half will be
made into two parts (instead of 7 in the current ECA –
see figure 3), hence with one remaining metallic ring
(so called field joint).

The required performance shall be with a 99% mission
success probability at minimum 2952 kg (i.e 4 x 738
kg (max mass of each Galileo FOC S/C)) with the
addition of the dispenser for carrying and separating
the 4 S/Cs i.e. the dispenser mass (447 kg) is not
included in the 2952 kg.

The choice for an ECA OoA fairing with field joint
was driven by constraints related to transport
containers and to the strong-back handling tools
available from ECA which can easily be modified and
re-used for the new OoA fairing. Yet, those
adaptations, wouldn’t be possible if the half fairing
were made of a single piece.

First launch should take place second half 2016. To be
able to launch Galileo FOC satellites, the Ariane 5 ES
launcher has been adapted, mainly in its upper part, for
performance (mass savings) and long duration mission
(thermal/electrical) purposes: these adaptations include
modification, VEB electrical and thermal design
adaptation, EPS ground heating power increase and
also electrical and thermal systems adaptations.
In line with ESA applicable “Requirements on Space
Debris Mitigation for ESA Project, the EPS (Etage à
Propergol Stockable) launcher upper stage has the
capability to be fully passivated after injection into the
graveyard orbit and satellite separation in order to
minimise the risk of debris generation: this
depressurisation, and last but not least full depletion of
the Système Controle d’Attitude (SCA) with
implementation of a dedicated pyrotechnic valve.

Figure 3 Ariane 5 ECA long fairing concept (current
an Out of Autoclave (OoA)
Obviously, the low shock separation system (HSS3+)
recently successfully implemented on Ariane 5 ES and
ECA launcher will be renewed on this new fairing (see

The mission is characterised by (see figure 4):


66th International Astronautical Congress, Jerusalem, Israel. Copyright ©2015 by de Chambure & al. ESA released to IAF to publish in all forms

Launcher configuration

a launch azimuth of about 35,5°,
a classical atmospheric ascent phase, with
relatively high level of aero-thermal fluxes
and aerodynamic pressure,
an EPC fall down location in the Pacific
ocean in an area close to the Equatorian
coasts and the Galapagos islands,
a first EPS boost of 11 minutes, just after EPC
separation (without any EPS delayed
ignition), which injects the Upper Composite
(EPS + Dispenser + 4 S/Cs) on a transfer
elliptical orbit with an apogee equal to the
targeted altitude,
a long coasting phase between the first and
the second EPS boosts, lasting 3 hours and 7
a second EPS circularisation boost of about
6.5 minutes, placing the Upper composite on
the required circular orbit,
and finally a satellites injection phase, with
the injection of each satellites pair separated
by 20 minutes, in the graveyard orbit, i.e
Galileo S/Cs will reach their final operational
orbit which is at an altitude of 300 km higher,
by their own propulsion system,
manoeuvres, the remaining Upper Composite
(EPS + Dispenser) is passivated.

The A5ES Galileo launcher is derived from A5ES
(Automated Transfer Vehicle) ATV launcher which
successfully flew 5 times and its configuration is
provided in the table 2 and in figure 5:
Ariane 5 ES Galileo Configuration
Upper Part

Medium size fairing (13 813 mm) with
HSS1 Horizontal Separation System

Specifically developed for Galileo.
Placed at the 2624 diameter on the EPS
cone, on which the 4 Galileo satellites are
A5ES/ATV VEB version adapted to the
Galileo mission with the main features:

A5ES/ATV with optimised cylinder
structure and a lighter cone (for
launcher performance improvement),

electrical design as of A5ES/ATV,
slightly adapted- see below),

removal of three SCA tanks, and
deletion of the SCA tanks Prosial
thermal protection

adapted equipment thermal design
performance improvement),

SCA-VUS idem to ATV but with
addition of one pyrovalve and a SCA
depletion line,
The storable liquid propulsive stage (EPSD) identical to the one of A5ES-ATV but
loaded with 10 tons of propellant and with
adaptation of the EPS ground tank heating
system including increased power and
ground heating duration that will depend
on the launch time (possibly up to 40 hours
cumulated time)

No de-orbitating neither re-orbitating of the Upper
Composite is foreseen, at any time of the mission.
The total mission duration is more than 4 hours from
lift-off until launcher passivation.


EPC-C with Vulcain 2 and R2f/R3f
tuning (i.e. A5 ECA configuration)



Figure 4: Galileo mission profile
Ground station network is defined as follows: Galliot,
Station Navale Ariane (SNA) sea-borne TM station,
Azores and New Norcia.

Family C. Identical to ATV.
Derived from ATV with following

CDC, Boitier de Puissance (BdP), i.e
power unit modified

Emitters switch on/off (UCTM
modules switch on/off idem ATV)

Implementation of pyro orders for
payload separation,

SCA depletion order

Table 2: Configuration for A5 ES Galileo Launcher


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Today, the Project is ready for the Launch System
Technical Review (LTQR) which is the final ESA led
review to confirm the qualification of the launch
system (Launch Vehicle and Ground Facilities) for the
Galileo FOC mission with Ariane 5 ES launcher.

Galileo SC & dispenser


Main challenges faced during the development were as
• launcher configuration: the launcher stages
configurations should be as much as possible
compatible with the ones of the other
launchers (A5ECA for the lower composite
and A5ES/ATV for the upper development
• injection accuracy which is crucial to
guarantee that the upper stage is left on a
stable graveyard orbit : this requirement led
to specific enhanced statistical Inertial
Reference System (IRS) performance studies
based on Ariane production feedback and to
operational constraints to perform the IRS
calibration two months before flight
• performance was one of the major drivers for
the launcher development logic. Performance
margin is today at + 66 kg and was achieved
 Use or re-use of existing launcher
elements, already qualified in the
frame of other A5 programmes,
when they are better adapted to the
Galileo mission than the ones used
for A5ES ATV launcher,
 Local optimisations (for all stages in
all engineering domains: thermal
design, structural design, electrical
design, functional design) of the
A5ES launcher as defined for the
ATV mission,
 Full exploitation of the activities
carried out in the frame of
performance plans (cf section I)),
 And last but not least the structural
lightening of the VEB structure
• thermal environment of the launcher and of
the spacecrafts due to the mission duration
(more than 4 hours) requesting detailed
thermal and electrical analysis and budget
assessment, especially as recommendation of
lessons learnt from the Soyuz launch failure
end of August 2014 (VS09)
• And last but not least the launcher-spacecraft
mechanical environment compatibility which



Figure 5: A5ES Galileo Configuration
The configuration of the launcher with emphasis on
the design of the newly developed items (dispenser,
and VEB) together with the flight sequence and the
program development were presented in [2]. In this
paper, the main challenges of the A5 ES Galileo
adaptation are presented as well as the main hardware
Development approach and challenges
The launcher qualification objective was to complete
the activities beginning 2015 in order to be able to
launch with A5 ES launcher four Galileo FOC
spacecraft’s as early as mid-2015, requiring flexibility,
lean management and limited modifications on Ariane
5 ES launcher, with well sized development efforts.
Hence, the development was carried out with
permanent interaction between launcher and stage
teams allowing a development with no PDR except for
elements undergoing major (re)design (i.e. dispenser
and VEB), i.e.


a Phase D – Qualification Phase from
beginning 2014 until beginning 2015, ended
by a launcher qualification review (CQL) .

a preliminary step in the period 2009-2010
leading to a Launch Concept Review (LCR)
validating the mission concept
a Phase C – Development Phase in the period
2012 till end-2013 2 ended by an Launcher
Critical Design Review (LCDR) and

There was a one year inactive period due to financial uncertainties


66th International Astronautical Congress, Jerusalem, Israel. Copyright ©2015 by de Chambure & al. ESA released to IAF to publish in all forms

is defined through five main requirements:
spacecraft shock levels, spacecraft acoustic
levels, interface loads between launcher and
spacecraft, spacecraft Quasi-Static Loads
(QSL) and acceleration levels. Interfaces
loads, QSL and acceleration levels are
extremely stringent notably due to
launcher-spacecraft coupling risks with the
thrust oscillation acoustic modes that occur
during the maximal acceleration phase of the

which might be impacted if the stack (dispenser S/Cs) is somehow stiffened.
At the end, after in depth review of the methodology
and values of the margin policy considered to derive
this status, it was concluded that from engineering
point of view the current spacecraft design is
compatible with the A5ES mechanical loading
environment with the current dispenser design and
with the appropriate Safety Factor ensuring adequate
reliability for flight, subject to the implementation of
an action plan including additional analysis and testing
as follows:

Mechanical environment compatibility

In the frame of the development, concerns have been
raised on the demonstration of the compatibility of the
Galileo satellites with Ariane 5 mechanical
environment (QSL, interface loads and I/F
accelerations) which were notably due to different
interpretation of the boundary conditions of the
mechanical interface requirements between the
launcher and the spacecraft.

In view of the criticality of the issue, a Galileo/Ariane
Mechanical Environmental Working Group was
created after the LCDR end 2013 to define and
monitor the technical path leading to complete
demonstration of the compatibility.

refined CLA (Coupled Load Analysis)
computation with reduced launcher loads on
launcher side
further refined analysis by Spacecraft
Authority of the remaining identified critical
area, incl. as necessary: Fitting Factor
refinement, considering actual critical insert
location, FEM refinement, incl. consideration
of panel/frame friction relaxing effect, Nonlinear analysis, Fail-Safe analysis for each
remaining critical insert and last S/C specific
static testing on S/C side.

This action plan and the proper demonstration of the
mechanical compatibility is on-going.

End June 2014, assessment of stress analysis of
Galileo S/C has confirmed the mechanical
compatibility of Galileo-FOC S/C with Ariane loading
environment, with the exception of local negative
Margins of Safety (MoS) on few inserts connecting the
S/C panels to the base frame, in the vicinity of the four
attachment points (S/C - dispenser interface). These
negative Margins of Safety of the inserts are mainly
driven by warpage phenomenon at the interface
(marginal MoS situation is obtained when considering
inertial loads only), thus confirming the interest of
minimizing the loads introduced by the dispenser at
the interface.

As mentioned above, the dispenser design was
resulting from an extended optimization loop
performed considering a wide set of constraints, such
as: mass, volume, dynamic behaviour w.r.t. launch
vehicle excitations and spacecraft, EPS qualification
domain, imposed HRS, accessibility and operation. In
that respect, the dispenser has primarily been designed
to stiffness and not to strength. Indeed, in order to
avoid potential coupling with the booster thrust
oscillation and hence dramatic increase of the launcher
loads onto the Galileo S/C interfaces, the dispenser
should be exactly tuned to specific frequencies at 29
Hz in longitudinal eigen-frequency (1st mode) and at
15 Hz in lateral eigen-frequency (2nd mode).

On dispenser side, additional local modifications were
assessed to decrease these launcher induced loads to
the S/C but it turned out that the rotational flexibility
of the Hold Down and Release System (HRS - heritage
and imposed design from the Soyuz dispenser) is a
major contributor to the local deformation in the
vicinity of the I/F points, so even with an infinitely
rigid dispenser, the insert problem on S/C side would
not be solved.

The dispenser made of hybrid concept (metallic/
composite) has been successfully qualified thanks to
an exhaustive test campaign, comprising dynamic
vibration tests, separation and shock test and finally
stiffness and strength tests. All these tests were
performed in the 2014 year at Airbus Safran Launchers
premises in St Médard en Jalles (France).

Additionally, another point of concerns was the
launcher EPS structure which has small margins and

First, a sine vibration test of the combined stack
(dispenser QM + 4 representative Galileo Satellite


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