ACTS

Artist impression of an ESA moonbase - ACTS is one of the projects within the framework of ESA's Aurora space exploration programme

ACTS (Advanced Crew Transportation System) is a crew transportation system which is jointly studied by the European Space Agency (ESA) and the Russian Space Agency (Roskosmos) with the objective to design a spacecraft for LEO operations such as servicing the International Space Station but also capable of exploration of the Moon and beyond. ESA officials have stated that this study is a response to NASA's Vision for Space Exploration and the Crew Exploration Vehicle which NASA wants to develop without participation of international partners. According to press releases that are available at the moment, JAXA could join the cooperation as well. ACTS is currently in an initial study phase, which shall last for two years from 2006 to 2008. The outcome of the study is planned to be presented to the ESA full memberstate conference in 2008.

Background

ACTS as answer to the CEV

Promotional picture for NASA's Vision for Space Exploration

In 2004 George W. Bush announced the Vision for Space Exploration, a program that includes the United States return to the Moon by 2020 and a manned mission to Mars by 2030.

For these purposes the Crew Exploration Vehicle is currently being developed. ESA officials have formally asked NASA to be part of this program for exploration, however received a negative response. Jean-Jacques Dordain, ESA's General Director stated with regard to this rejection by NASA: "I have been told by Mike Griffin and Marburger that the CEV is not for international cooperation. But if Europe is not involved in the next-generation transportation systems, we will stay forever a second-class partner."http://www.planetary.org/news/2006/0628_Europe_and_Russia_Join_Forces_to_Study.html

In a July 2006 interview with New Scientist, NASA Administrator Mike Griffin however suggested interest in international cooperation in the general context of NASA's Moon exploration plans. "The US will return to the Moon but we think we will do it better, that it will be more rewarding for all, if it can do it in the company of as many of our ISS partners as we can, and with new partners."http://www.newscientistspace.com/article/dn9582-nasa-seeks-help-for-human-exploration-of-mars.html In this statement Griffin speaks of a general cooperation, not a cooperation in developing the CEV, the actual vehicle to be used for Moon missions, which will be an entirely American built spacecraft.

Because the CEV will not be developed or used in cooperation with ESA, ESA faces a major obstacle for continuation of its manned spaceflight program with the end of the Space Shuttle program by 2010 and the contemplated end of the International Space Station program by 2015/2016.

Cooperation with Russia

Winged Kliper mockup at the Le Bourget Air Show

Since 2004, ESA has been in talks with Roskosmos on a cooperation for the development of Kliper, the Russian successor project to the Soyuz spacecraft which has been in service for nearly 40 years. While ESA's management was enthusiastic about this cooperation, ESA memberstates turned down funding for a design and collaboration study in December 2005, mainly because certain memberstates did feel that ESA would just be a minor industrial contributor to the program, while Russia would actually develop and design the Kliper spacecraft.

After the December 2005 rejection of Kliper by ESA, Jean-Jacques Dordain emphasized that a collaboration with Russia on a new spacecraft could still be decided in June 2006. On June 13, 2006 the press reported that the winged Kliper project has been replaced by a study to develop a capsule under the Advanced Crew Transportation System program that ESA is funding.http://www.flightglobal.com/Articles/2006/06/13/Navigation/177/207228/Kliper+dropped+for+lunar+capsule.html It is however necessary to understand that Kliper was a Russian program that might still be funded entirely by Roskosmos - this is however unlikely to happen if Russia and Europe really go forward with ACTS together. Reasons for going with ACTS include that it gives Europe the possibility to be a full partner in a Russian-European program, because the modular structure (see below) allows to divide responsibilities for design to each partner (for instance Russia could be in charge of the overall design of the reentry capsule, while ESA works on the habitation module etc.)

About â‚¬15 million have been currently pledged for the ACTS program on ESA's regular meeting on June 21 and June 22, 2006. Further funding of the study will be asked for at the next ESA meeting in July. Both partners, Russia and ESA, will bear their own costs in the first 2 years of the program. "We are now entering a phase of working with the Russians where we will establish a preliminary design of the vehicle, establish all the legal framework for the operation, delineate the work share for the parties, and outline the aspects of development," said Manuel Valls, head of Policy and Plans Department in ESA's Directorate of Human Spaceflight, Microgravity, and Exploration Program.

On July 4, 2006 Russian media reported that the head of the Russian Space Agency Anatoly Perminov has met with Jean-Jacques Dordain to discuss the ACTS proposal, however no agreement was signed between the Russians and Europeans after that meeting.http://www.mosnews.com/news/2006/07/04/russianasaiss.shtml

On July 18, 2006 Anatoly Perminov, head of Roskosmos, announced that the Russian tender for the Kliper spacecraft has been cancelled. http://www.flightglobal.com/Articles/2006/07/18/Navigation/177/207935/Farnborough+Russia's+Federal+Space+Agency+cancels+manned+spacecraft.html It was noted that the ACTS proposal has gained more support among ESA memberstates than the Kliper design.

Farnborough Air Show

Jean-Jacques Dordain announced on the Farnborough Air show on July 25, 2006 that the collobarative study together with Roskosmos on the ACTS spacecraft will begin in September 2006 and will end early in 2008: So in 18 months' time we will have got a proposal to make to our ministers for the development of such a vehicle. http://www.flightglobal.com/Articles/2006/07/25/Navigation/177/208008/Farnborough+Crew+transport+work+to+start.html It was confirmed that on ESA's side of this study will be funded with 15 million EUR by a total of seven ESA member states. The work areas of the study are:
* preliminary system design examining the vehicle's configuration
* detailed subsystem design including a docking mechnism
* development of co-operation mechanisms and agreements, as well as workshare decisions for a full-scale development
* manned lunar flights

Overall Design

Three module design http://www.belspo.be/belspo/eisc/pdf/docu2p_eisc/DeWinne.pdf

The Soyuz three module design will be followed by ACTS as well

ACTS, designed for exploration missions, will feature as re-entry vehicle an improved, Soyuz-type capsule, having increased resources for extended missions duration, improved thermal protection system for reentry into Earth's atmosphere with a higher velocity than just from LEO, new interplanetary navigation systems and possibly an increased size to accommodate a larger crew of 4 members. It will also include a habitation module (like the orbital module on the Soyuz) large enough to accommodate the necessary equipment and resources, as well as to provide the necessary living space to the crew for the longer duration missions. A service module, including attitude control thrusters, oxygen tanks, TCS, Motion Control Systems data handling and distribution, command system, telemetry and feedback the main propulsion system and other subsystems, including solar arrays, electrical power control system, etc. http://www.flightglobal.com/Articles/2006/06/13/207228/Kliper+dropped+for+lunar+capsule.html

The three-part design of ACTS is similar to the one used on Soyuz. The advantages of using such a system instead of the two-part CEV structure (only a crew module that is also used as re-entry module and one service module), is that the re-entry module can be stripped down to a minimum size and weight, as it is not necessary for the crew to stay in the re-entry module for the whole mission duration but the crew can use the habitation module as well. Because the habitation module is discarded before reentry into Earth's atmosphere, it can be made out of light-weigh material that does not need to withstand the forces of a re-entry. This approach reduces overall weigh of the spacecraft.

The re-entry module

Soyuz uses a bell-shaped re-entry module that has space for three cosmonauts. Its weight is approximately 2.8 metric tons. The ACTS study will have to decide whether they are using the same bell-shaped form for the 4 crew re-entry module or which other configuration the re-entry module will take (cone-shaped such as the Apollo spacecraft or the CEV). What is clear today is that the re-entry module will be a capsule and not a lifting body, which reduces complexity of the system. While the CEV crew module is currently designed to weigh over 9 metric tons, the ACTS re-entry capsule will probably weigh much less, as living space for the whole spacecraft is divided into the re-entry module and habitation module.

ATV - heritage to be used for ACTS

The habitation module

For spaceflights beyond LEO, it is necessary to accommodate certain equipment and appliances (toilet etc.) in a spacecraft. This habitation module could be derived from hardware that has already been developed by ESA, that is the Automated Transfer Vehicle or the Columbus Orbital Laboratory.

The service module

Power and propulsion needs to be provided by another module. Heritage for this module may come from both the Soyuz spacecraft or the Automated Transfer Vehicle. In light of a mission beyond LEO this module will however be by far the largest of the three modules the spacecraft consists of (see below).

Existing launchers such as Ariane 5 or Proton or Soyuz rockets are contemplated to be used for ACTS

Missions beyond LEO

Launchers

To understand the ACTS mission parameters it is first important to understand what limitations ACTS will have to deal with. Manuel Valls, head of Policy and Plans Department in ESA's Directorate of Human Spaceflight, Microgravity, and Exploration Program noted on the question of available launch vehicles for the ACTS spacecraft that "although nothing at this stage is definitive, [...] both the Russians and we think that it is only prudent, and most efficient and effective, to go with 2 stages and not one. The 1-stage has been done already with Saturn V and Apollo. To do that now would entail the development of quite a new launcher and that will take time and money like hell, if I may say. Going with two stages is far more effective [...] because we could use â€" and this is our intention â€" existing launch vehicles or launch vehicles with minimal development." This means that ACTS will have a tight mass budget, as only launchers with a maximum payload capacity in the class of Ariane 5, Proton or Angara will be available for a launch. With '2 stages' and LEO docking that means that ACTS together with an Earth Departure Stage will not be able to weigh more than about 45 to 50 metric tons in LEO (note however that this is just for the lunar spacecraft, a lunar lander is not integrated in this calculation).

An ESA presentation from June 13, 2006 however presents a lunar orbital mission of the ACTS spacecraft with 3 launches, of that 2 are propulsion modules to propel the spacecraft to a trans-lunar trajectory. Such a scenario, while more complicated than the 2-stage approach mentioned by Manuel Valls, gives more leeway in terms of the ACTS' mass budget.

Scaling the ACTS for a lunar mission

lunar orbit insertation architecture with 3 launches (the lunar lander in this picture is only for illustration purposes and is not included in the 3 launches scenario and has to be deployed to the moon separately)

With the limitations on launch vehicles in mind, the size and weight restrictions of the ACTS spacecraft allows to give a good sense of how large the spacecraft may actually be: http://www.mars-lunar.net/Lunar%20Mission%20models/lunar.orbit.and.back.pdf Spreadsheet for lunar orbit mission delta-v and mass of spacecraft (pdf)
* A two launcher scenario would bring an Earth Departure Stage (EDS) to LEO with one launcher and the ACTS spacecraft with the other launcher. The EDS would be either a derivative of a Block-D or a LOX/LH2 upper stage such as the KVRB http://www.astronautix.com/stages/angakvrb.htm which is currently in development by Krunishev for the Angara rocket. One LEO docking would be needed, with the ACTS spacecraft doing the active docking and the EDS being equiped with a passive docking mechanism. After that the ACTS spacecraft would be propelled to a trans-lunar injectory (TLI). Assuming that the partners would develop a 25 ton EDS so to fit it to the maximum LEO payload of Ariane 5 or Angara 5, the ACTS spacecraft would be limited to a 16-17 metric ton mass at the outmost if only the EDS would do the TLI burn - in this scenario the ACTS spacecraft could be launched by a Zenit rocket or a Soyuz-3, a Soyuz derivative rocket that is currently planned to be developed in the 2011-2015 timeframe and would be able to carry up to 16-17 tons into LEO http://russianspaceweb.com/soyuz3_lv.html. It is however a possibility that the ACTS spacecraft does part of the TLI burn with its own service module, in which case the ACTS spacecraft could be scaled up to the max payload of Ariane, Proton or Angara as well, or a second EDS stage is launched together with the ACTS craft on the 25ton launcher.
* In any event, to reach (Lunar orbit injection (LOI)) and leave (Trans-earth injection (TEI)) lunar orbit after TLI the minimum required delta-v is about 2.5 km/s. With storable propellants (isp 360 sec) at least 50% of the spacecraft mass needs to consist of propellant. A 17 ton spacecraft would thus need to consist of at least a 10-12 tons service module (8.5-9 ton of propellant and the rest structure and power supply). This leaves about 5-6 tons for both the re-entry and the habitation module together (note that the Soyuz re-entry capsule and orbital module already weighes 4.2 tons while only being used for short LEO mission with 3 crew members). The Soyuz re-entry capsule weighs 2.8 tons, enlarging it to accommodate 4 crewmembers and enhancing the heatshield for rentry from TEI (higher velocity) will at a minimum require it to weigh 3.5 tons. That leaves 2-2.5 tons for the habitation module, compared to the 1.3 tons of the Soyuz orbital module an increase that could work for a lunar mission. The constraints outlined above are lower if the ACTS spacecraft is scaled to the max mass of Ariane or Angara and does part of the TLI burn or a second EDS is launched together with the spacecraft, in this case the mass of the ACTS spacecraft would be about 20 tons after completed TLI-burn. In this scenario about 6.5-7 tons of the spacecraft could be allocated to the re-entry capsule and habitation module.
* Another scenario would be a three launch mission involving the Soyuz-2 vehicle in a further developed stadium (a Soyuz 2-3 with a LEO payload mass of 12.7 t from Kourou is currently in development and scheduled to be ready in 2010 http://www.russianspaceweb.com/soyuz2_3_lv.html). In a 3-launch scenario, the crew would be launched on the ACTS spacecraft on the Soyuz and two EDS (launched by Ariane 5, Proton or Angara) would be utilized for the TLI burn and LOI burn. One of the unmanned launches would carry both an EDS and a TEI stage. The advantage of this strategy would be that the manned spacecraft could be launched by the Soyuz (although enhanced, the Soyuz 2-3 would still have the same dimensions as the current Soyuz), which has a 40 year track record of human flight.

Scenario	Launch option availability	Mass in LEO	Maximum mass of ACTS Crew Module + Habitation Module	Delta-v provided by EDS for TLI burn	Delta-v provided by ACTS Service Module for TLI burn	Mass after TLI burn	Mass after LOI burn!Mass after TEI burn, propellant used for plane changes and dockings in LLO
Soyuz-3 and Ariane 5/Angara 5 class option	Soyuz-3 not available before 2015, if at all, Angara 5 not before 2012	40 t (ACTS spacecraft = 16 t)	5.5 t	3.2 km/s	0 km/s	16 t (with dry EDS 19.5 t)	12.5 t (ACTS SM does LOI)	8 t (ACTS SM does TEI)
2Ã—Ariane 5/Angara 5 class option	Ariane 5 to 3Â°inclination (25t version) available with minimal modifications, Angara 5 not before 2012	50 t (ACTS spacecraft = 25 t)	7 t	2.4 km/s	0.8 km/s	20 t (dry EDS jettonised before second burn)	16 t (ACTS SM does LOI)	10 t (ACTS SM does TEI)
Soyuz-2-3 and 2Ã—Proton (rocket)/Ariane 5-ATV class option	Soyuz 2-3 available in 2011-2015 timeframe, Proton/Ariane 5-ATV currently available	55 t (ACTS spacecraft = 12.7 t)	8 t	3.2 km/s (1.6 km/s by EDS-1, 1.6 km/s by EDS-2)	0 km/s	23 t	18.5 t (dry EDS-2 jettonised - EDS-2 does LOI)	10.5 t (dry TEI-stage jettonised after TEI, ACTS SM does part of TEI)
Soyuz-2-3 and 2Ã—Ariane 5/Angara 5 class option	Soyuz 2-3 available in 2011-2015 timeframe, Angara 5 first launch not before 2012	62 t (ACTS spacecraft = 12.7 t)	9-9.5 t	3.2 km/s (1.9 km/s by EDS-1, 1.3 km/s by EDS-2)	0 km/s	27 t	21 t (dry EDS-2 jettonised - EDS-2 does LOI)	12 t (dry TEI-stage jettonised after TEI, ACTS SM only used for course corrections)

A lunar lander (LM)

Lunar Lander launch scenario using Soyuz and Ariane 5 from Kourou

Press coverage

Press coverage of the ACTS study up to now only speaks of the ACTS spacecraft itself, not of any other equipment and vehicles needed for a lunar mission (apart from just a lunar flyby or lunar orbital mission). If the ACTS spacecraft is launched as outlined above, the best possible solution for a lunar landing is to rendezvous the ACTS spacecraft with a Lunar Lander in Low Lunar Orbit (LLO). Otherwise three or more dockings would be required in LEO which leads to complications in mission timeline and launch schedule. With the LLO approach the overall dockings involving the manned ACTS spacecraft would be at a minimum two, in LEO with the EDS and in LLO with the LM.

Advantages of LLO rendezvous

There are several advantages of an LLO-rendezvous instead of 3 or more LEO rendezvous:
* With an LLO rendezvous, the ACTS spacecraft is independent of the actual design of the LM. That leaves the design of the LM flexible and allows for the use of different LM vehicles for different missions. In comparison, the CEV/LSAM design of NASA is interconnected in that the LSAM is used for the LOI burn. A light variant of the LSAM for crew transportation to a lunar base would alter NASA's overall lunar landing architecture and in light of the use of the super-heavy launcher Ares 5 would not reduce launch costs once lunar missions would only ferry new crews to a moon base instead of independent missions.
* From different launch sites, different LEO inclinations are the most payload effective. Kourou's proximity to the equator allows Ariane 5 to lift more payload to LEO into a 3Â° inclination than a higher inclined orbit. If both the ACTS spacecraft and the LM would be docked in LEO, a Russian-European cooperation would need to decide which 'compromise orbit' they would chose for docking spacecrafts and EDS-stages launched from Kourou and Baikonour resulting in LEO payload capacity losses of well over 10%. Instead launching the ACTS spacecraft and its EDS from one spaceport and the LM with its EDS fro the other spaceport and dock them in LLO does not encounter the problem of different launch site locations.

LM launch options

The Apollo LM weighed about 15 tons and was designed for a max. 3 day mission for 2 crew members

A heavy variant of the LM could be deployed to lunar orbit in the same way the ACTS spacecraft is. One launcher would bring the LM into LEO and another launcher the EDS (the same EDS used for the ACTS spacecraft). Either the LM does part of TLI (like the ACTS spacecraft) itself or a second EDS is used for TLI and LOI. Depending on the launchers used, the LM in lunar orbit could weigh up to 16-17 metric tons (see table below). In the heaviest 2-launcher scenario this is slightly more than the mass of the Apollo LM, which weighed 15 metric tons. It should be noted, however, that today the isp (specific impulse) for storable propellant (which need to be used for a predeployed LM) is higher than the 311 sec isp the Apollo LM engines could provide. This leaves a higher cargo and crew capacity to lunar surface with about the same mass as the Apollo LM had, which would allow lunar landings of 3 or 4 astronauts/cosmonauts or landings with 2 crewmembers with a longer mission duration.

In a light variant an LM could be directly launched to a TLI (the most capable Ariane 5 (ECA) today could launch 10.5 tons to GTO, from where this LM would do the rest of TLI and LOI and would end up with about 6tons in LLO - see calculations below). Designed as an open 'bare bones' lunar lander (often called a 'rocket chair'), this vehicle could be used to bring astronauts or cosmonauts to a predeployed lunar base in a more cost-effective way, as the total mission scenario would only use 1 launcher for the LM. If a moon base has already been previously installed, it would just waste mass to include a pressurized module on the LM, as it is solely used to transfer the crew from LLO to the base and back, but such pressurized module would not be used for anything else.

Scenario	Launcher availability	Mass in LEO	Mass of LM in LEO	Delta-v provided by EDS for TLI burn	Delta-v provided by LM (or second EDS) for TLI burn	Mass of LM (together with EDS-2, if applicable) after TLI burn	Mass of LM (without EDS-2, if used) after LOI burn!Mass of LM (overall mass with landing stage dry mass) on lunar surface
Single Ariane 5-ECA launch option	launch option currently available	N/A (direct GTO injection - Ariane 5 ECA upper limit for GTO 10.5 tons)	N/A (no LEO injection)	2.4 - 3.2 km/s (depending on only GTO or TLI by upper stage of Ariane)	0-0.8 km/s	8.5 tons	6.5 tons	3.5 tons
Single Ariane 5-ECB launch option	Ariane 5 ECB development on hold since 2003 - under review	N/A (direct GTO/TLI injection - Ariane 5 ECB upper limit for GTO 12 tons)	N/A (no LEO injection)	3.2 km/s (restartable upper stage)	0 km/s	10.2 t	8 tons	4.3 tons
Soyuz-2-3 and Ariane 5-ATV/Proton (rocket) class option	Ariane 5 ATV/Proton (both 21 tons to LEO 51Â° inclination) available, Soyuz 2-3 available in 2011-2015 timeframe	34 tons	12.7 tons	3.2 km/s	0 km/s	12.7 tons (dry EDS-1 jettonised after TLI burn)	10 tons (dry EDS-2 jettonised after LOI burn)	5.3 tons
-	Soyuz-3 and Ariane 5/Angara 5 class option	Soyuz-3 - not available before 2015, if developed at all, Angara 5 first launch not before 2012	40 tons	16 tons	3.2 km/s	0 km/s	16 tons (dry EDS jettonised after TLI burn)	12.5 tons	6.5 tons
2 x Proton (rocket)/Ariane 5-ATV class option	launch option currently available	42 tons	13.5 tons	2.2 km/s (EDS-1)	1 km/s (EDS-2 does second TLI burn)	17 tons (dry EDS-1 jettonised before second TLI burn)	13.2 tons (dry EDS-2 stage jettonised)	6.8 tons
2 x Ariane 5/Angara 5 class option	Ariane 5 to 3Â° LEO inclination (25 tons) available with minimal modification, Angara 5 not before 2012	50 tons	25 tons (optional 16tons: a second smaller EDS stage launched together with the LM)	2.4 km/s	0.8 km/s (or 0.8 km/s by EDS-2 with isp 460)	20-21 tons (dry EDS-1 jettonised before second TLI burn)	15.5-17 tons (dry EDS-2 stage jettonised)	8-8.5 tons

* RSC Energia: Concept Of Russian Manned Space Navigation Development
* ESA presentation on ACTS dated June 13, 2005 (pdf)
* Europe and Russia Join Forces to Study Advanced Crew Transportation System
* Russia FSA cancels manned spacecraft tender
* ESA, Russia to Collaborate on New Spacecraft Design
* ESA to finalise manned capsule contributions at July meeting
* Kliper dropped for lunar capsule
* http://www.mars-lunar.net/Lunar%20Mission%20models/lunar.orbit.and.back.pdf Spreadsheet for lunar orbit mission delta-v and mass of spacecraft (pdf)

ACTS: Encyclopedia BETA

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