Dragon Endeavour performs port relocation to clear way for Starliner

The SpaceX Crew Dragon Endeavour vehicle has swapped docking ports aboard the International Space Station… The post Dragon Endeavour performs port relocation to clear way for Starliner appeared first on NASASpaceFlight.com.

Dragon Endeavour performs port relocation to clear way for Starliner

The SpaceX Crew Dragon Endeavour vehicle has swapped docking ports aboard the International Space Station in preparation for the upcoming Starliner OFT-2 mission. The 45-minute maneuver began at 10:45 UTC with undocking from the forward port of the Harmony module.

After undocking, Endeavour backed away from the ISS to a distance of 220 meters before maneuvering towards the Zenith port for re-docking. Endeavour docked back to the ISS at 11:35 UTC.

Aboard Dragon for the maneuver will be SpaceX Crew-2 astronauts Shane Kimbrough and Megan McArthur of NASA, Thomas Pesquet of the ESA, and Aki Hoshide of JAXA. All crew must be aboard Dragon so that they are able to return to Earth in the event of a failed redocking, rather than being stranded on the ISS without a ride home.

The crew was also wearing their SpaceX pressure suits in order to protect them from the unlikely event of a depressurization event, should there have been an off-nominal approach that results in a contact between Dragon and the ISS.

The relocation itself began at 10:45 UTC when Endeavour undocked from the Pressurized Mating Adapter-2 (PMA-2) / International Docking Adapter-2 (IDA-2) port on the Forward side of the Harmony module, the port to which it has been docked since it’s arrival at the ISS on 24 April.

Endeavour then backed away from the ISS to a distance of 220 meters, at which time it was commanded to perform an automated 90-degree “flyaround” maneuver in order to align with the PMA-3/IDA-3 port on the Zenith, or space-facing, side of Harmony.

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  • Endeavour then initiated an approach to re-dock with the ISS at 11:35 UTC. After a successful docking, hatches will be re-opened after the standard vestibule pressurization and leak checking procedures have been performed.

    This is not the first time Crew Dragon has performed a port relocation – Resilience also performed the same maneuver on April 5 to clear the PMA-2 port for the arrival of Endeavour. Relocations of US crew vehicles is becoming commonplace on ISS as Crew Dragon, Cargo Dragon, and Starliner spacecraft share the only two available docking ports to American docking vehicles.

    Other ports on the ISS are only compatible with either vehicles which berth to the station with the help of Canadarm2, such as Northrop Grumman’s Cygnus and the upcoming Sierra Nevada Corporation Dream Chaser and Japanese HTV-X cargo spacecraft, or only compatible with Russian Soyuz and Progress spacecraft on the Russian segment of the station.

    Today’s relocation was performed in order to clear the PMA-2 port for the arrival of Boeing’s Starliner vehicle on the uncrewed OFT-2 mission, set to launch on July 30 for a docking to the ISS on July 31.

    Render of Starliner approaching the forward port while Crew Dragon sits docked to the Zenith port – via Mack Crawford for NSF/L2

    One issue with vehicles docking to the PMA-3/IDA-3 port on the Zenith side of Harmony is that the station’s Ku-band Space to Ground Antenna (SGANT), located on top of the Z1 Truss, can get blocked by approaching vehicles.

    Since the SGANT must point toward space in order to communicate with the Tracking and Data Relay Satellites (TDRS) located in geosynchronous orbit, any vehicles approaching the ISS from above may come between the SGANT and the TDRS, depending on the position of the TDRS and the timing of the docking.

    This presents signal reflectivity issues, whereby the high-power Ku-band energy may be bounced back into the SGANT, damaging it’s sensitive autotrack sensors.

    Therefore, the SGANT must be pointed away from the approaching vehicles, a procedure known as “masking,” whereby the SGANT is prevented from pointing anywhere toward the vehicles’ approach corridor.

    This means that live downlink of approach and docking video to the ground is not always possible, as this can only come via Ku-band signal from the SGANT.

    The crew aboard the ISS can still receive live video from the approaching vehicle’s cameras, as that is relayed via the Common Communications for Visiting Vehicles (C2V2) link using the S-band antennas.

    Diagram of Endeavour’s relocation maneuver – via NASA

    However, controllers on the ground are unable to see live footage from the docking cameras due to the lack of a Ku link, and for this reason PMA-2 can be the preferred port for some dockings – especially test flights – as, being located on the Forward side of Harmony, there are no SGANT masking issues with vehicles using this port.

    This is why the first, uncrewed docking of Starliner to the ISS will use the PMA-2 port, just like SpaceX’s Crew Dragon vehicle did on the uncrewed Demo-1 mission.

    PMA-2 is also the preferred port for OFT-2 as Starliner’s flight software has been certified for a PMA-2 docking – although the operational version of the vehicle will have the ability to dock to any port. Additionally, PMA-2 offers better lighting conditions, and doesn’t have issues with sensor obstruction due to approaching vehicles not being pointed toward Earth as they are for PMA-3 dockings.

    After the departure of Starliner, there could possibly be a relocation of Endeavour from PMA-3 back to it’s original port of PMA-2 again. This would be to clear PMA-3 for the arrival of the CRS-23 Cargo Dragon in late August, should any unpressurized cargo be launched in Dragon’s trunk that would need to be accessed by the station’s robotic arm.

    PMA-3 is the preferred port for Cargo Dragons when there is a need for robotic arm access to Dragon’s trunk. In order to access trunk cargo with Dragons docked to PMA-2, the station’s arm would have to stretch far forwards and double back on itself, something it does not have the reach to do.

    After the departure of CRS-23 Cargo Dragon, the next crew rotation will arrive on a Crew Dragon on the SpaceX Crew-3 mission, launching from the Kennedy Space Center in Florida no earlier than 31 October.

    (Lead photo of Endeavour’s original docking on 24 April – via NASA)

    The post Dragon Endeavour performs port relocation to clear way for Starliner appeared first on NASASpaceFlight.com.

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    Nauka science module’s launch to ISS arrives

    Good things come to those (modules) that wait.  On July 21, at 14:58:21 UTC (10:58:21… The post Nauka science module’s launch to ISS arrives appeared first on NASASpaceFlight.com.

    Nauka science module’s launch to ISS arrives

    Good things come to those (modules) that wait.  On July 21, at 14:58:21 UTC (10:58:21 EDT), a Proton-M rocket is due to launch from the Baikonur Cosmodrome to take the first Russian ISS module in 11 years to orbit.  The moment marks a major milestone for Roscosmos, which was originally slated to launch the module in 2007.

    After launch and orbit insertion, the module, MLM-U Nauka, will perform an eight day phase to the Station for an automated docking on July 29 to the nadir docking port of the Zvezda service module, a port currently occupied by the Pirs module.

    Nauka – the “long suffering” module

    Upon arrival, Nauka will become the third largest module of

    The main task for the Nauka module will be to conduct scientific experiments.  The pressurized compartment of the module contains 21 universal working places (URM), including four locations with sliding shelves, a glove box, a frame with an automatic rotating vibration-proof platform, and a porthole with a diameter of 426 mm for visual and instrumental observations.

    Equipment to allow easier replacement of old experiments with new ones is also incorporated into Nauka’s internal design and is based on lessons learned from the early years of the ISS program. 

    An additional 16 URMs are located on the outer surfaces of the module, which also has an airlock chamber and a European manipulator robotic arm, which will allow operations with experiments in the vacuum of space without performing EVAs.

    The full name of the new module, MLM-U “Nauka” (which means “science”), stands for “Multifunctional laboratory module Nauka, improved.”  However, it is also somewhat lovingly referred to as the “long-suffering module” due to its numerous uses and launch date changes.

    Initially, Nauka was built as a backup for FGB Zarya, the first module of the ISS.  Construction started in 1995, with a design based on the hull of the Soviet cargo ship TKS, itself a part of the Almaz military program which included orbital stations, a supply cargo ship, and crewed ships with reusable descent modules. 

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  • Nauka is in fact the last surviving, active part of the Almaz program, excluding the hulls and ships which were sold to the Excalibur-Almaz company and to museums for exhibition.  Nauka’s original use as a back up Zarya stemmed from the critical nature of the Zarya module to the overall ISS design; given a launch failure would have set the ISS program back years, Nauka was built as a “quick replacement” to Zarya in case the original module was lost in a launch failure.

    Zarya successfully launched on a Proton-K rocket from the Baikonur Cosmodrome on November 20, 1998 and was grabbed by Shuttle Endeavour’s robotic arm, or Canadarm, on December 6 and manually docked to the Unity module.  At this point, Nauka, or FGB-2, as it was called originally, was already 80% complete and now no longer needed for its primary back-up role. 

    The same year as Zarya’s launch, the Khrunichev Center proposed creating a scientific module for the U.S. segment of the Station based on FGB-2 to replace Destiny, delivery of which from Boeing was running late.  While an agreement of intent was signed, Destiny was completed and successfully sent into orbit in 2001 while FGB-2 remained on Earth. 

    Not wanting to discard a nearly complete module, in 2004, Roscosmos decided to create a laboratory module based on it for the Russian segment of the ISS.  To do this, FGB-2 had to be completely reequipped — all systems that would have been needed as a Zarya back-up but that were no longer necessary for its use as a science module were removed to make room for scientific equipment.  

    Nauka undergoing checkouts and outfitting in 2020. (Credit: Katya Pavlushchenko)

    At the same time, Roscosmos partnered with the European Space Agency to install an 11 meter European robotic arm, the ERA, on the new module.  The European arm will be able to help cosmonauts access locations on the Station during spacewalks and remove and install equipment placed on the outer surface of the ISS. 

    The re-equipment process for FGB-2 was anticipated to take three years, resulting in a 2007 launch.  The module was formally renamed at this time to MLM Nauka.  However, as is often the case in the space industry, the proposed deadlines turned out to be too optimistic.  

    By 2006, two years into the refit, the launch was postponed to 2009 and then again to 2012.  In December 2012, with another launch delay added, the module was finally moved from the Khrunichev Center, where it was built, to RSC Energia for testing. 

    Here, a problem was discovered.

    In June 2013, RSC Energia specialists reported a large number of defects had been found in the module.  In particular, metal shavings were discovered contaminating fuel lines, which caused the launch date to be postponed to 2014 and the module itself was returned to the Khrunichev Center for pipeline cleaning.

    The procedures and bureaucracy took several months, including a slight rename to the module.  According to documents, since the module was already manufactured and fully paid for, it was legally necessary to call its repair an “upgrade.”  From that moment on, the letter “U,” which means “improved,” appeared in the name of the module. 

    Nauka, just before encapsulation for launch. (Credit: Roscosmos)

    At the end of 2013, the module was finally transported back to the Khrunichev Center and a new launch date was set for 2016.  However, checkout of all systems took three years, due to lack of funding, necessitating another slip to the launch date.

    In April 2017, specialists at the Khrunichev Center announced that the same metal shavings previously found in the fuel pipelines were found in the propellant tanks of the module as well.  This statement, combined with another long-term postponement of the launch, led many experts to question if Nauka would ever fly to orbit. 

    However, the new issue with the tank posed a problem: the propellant tanks for Nauka were made in the 1990s on equipment that no longer existed in 2017 at a factory that was already demolished using technology that now remained only as drawings.

    The module’s bellow refillable propellant tanks are 400-liter tanks installed on the outer surface of the housing of the module. These tanks are fueled with unsymmetrical dimethylhydrazine and dinitrogen tetroxide.  From them, fuel travels to the orbital maneuvering engines, which are necessary for orbit correction and rendezvous maneuvers. 

    Officials were concerned that the metal shavings could travel into the engines and contaminate them, preventing the module from being able to dock with the ISS and burning up in the dense layers of the atmosphere instead.

    At first, engineers wanted to flush the tanks under pressure, but this procedure was not successful.  After that, cutting, washing and re-welding of the tanks was tested on a mockup of the module, but it was found that after such a procedure it would not be possible to restore the tanks to their proper condition and strength.  

    An internal cut-way showing the layout of Nauka. (Credit: Roscosmos)

    Additional ideas were considered to:

    • replace the existing propellant tanks with ones made for the Science and Power Module (NEM).  This was rejected because the tanks of NEM have a different diameter and it would require a redesign of the module and the fairing for Nauka.
    • replace the propellant tanks of Nauka with the ones from an upper stage Fregat.  A series of spherical Fregat tanks would have been fitted into the current dimensions of the module, but they would not be refuelable and would have demanded significant improvement of the whole propellant system of the module.
    • send Nauka to orbit with its regular propellant tanks as they were.

    The possibility of manufacturing new propellant tanks using old technology was not considered due to the lack of equipment for their production.  As a result, it was decided that Nauka would fly with its regular propellant tanks, which would now be used only once. 

    At the same time, numerous experts in the space industry noted that contamination with metal shavings of 100 microns in size could not affect the engines of the module and that given similar designs it is possible a similar contamination existed in the tanks of Zarya and in the tanks of the Mir station modules but that the older quality control methods couldn’t detect the shavings.  

    Some experts also noted that metal shavings are a consequence of the very design of the tanks and are formed with every movement of the bellows; therefore simply building new ones would not solve the issue.

    Nevertheless, over the intervening three years, all the original pipelines and valves were dismantled and replaced with new ones.  At the beginning of 2020, specialists began a new testing campaign of the Nauka module, and a new launch date was set: May 2021.  

    The tests lasted slightly longer than expected, and the new official launch date was set for July 15, 2021.  But the adventures of the “multi-suffering” module didn’t end there. 

    In early July 2021, when the fairing had already been installed over the module for launch, Nauka was suddenly returned to the assembly building.  According to the official version, shortcomings were found, but no further information was stated at first.

    The RussianSpaceWeb portal published a report stating that final assembly workers forgot to install the thermal vacuum insulation covers on the star tracker and infrared sensors.  This issue was missed by Roscosmos and apparently only spotted by spaceflight enthusiasts from images posted by the Russian space agency.  The module was returned to the assembly building, and the launch date was postponed again to July 21, 2021.

    Launch

    At 20,350 kg mass, Nauka is near the upper limit of what the Proton-M rocket can deliver to low Earth orbit (LEO). 

    With a lift capability of 23,000 kg to LEO, the Proton-M will lift off from Site No. 200/39 at the Baikonur Cosmodrome, pitching onto an azimuth, or compass heading, to achieve a 51.6 degree inclination orbit.

    The Proton-M for this mission is a three stage-to-orbit rocket, with all stages burning the highly toxic dinitrogen tetroxide and unsymmetrical dimethylhydrazine mixture.

    The first stage employs six RD-275M engines arranged around the circumference of the first stage tanks.  A hot-stage event, where the second stage ignites while the first stage is still attached and firing, will hand off between the two lower stages.

    The Proton-M rocket with Nauka safely in its payload fairing sits on Site No. 200/39 at the Baikonur Cosmodrome surrounded by the Kazakh steppe. (Credit: Roscosmos)

    Payload fairing separation will occur at an altitude of 138 km approximately 330 seconds into the flight.

    The third stage, 8S812, will then complete the launch sequence, placing Nauka into an almost complete parking orbit of 190 x 350.1 km in the orbital plane of the International Space Station after a 580 second ascent

    Once in orbit, Nauka will deploy solar panels and begin eight days of system checkouts and rendezvous burns to gradually raise its orbit up to the 415 km altitude of the Station.  If all goes to plan, Nauka will dock itself to the ISS — under the watchful eye of Mission Control, Moscow, and the Russian crew onboard the Station — on Thursday, July 29.

    However, Nauka’s destination on the Station is currently occupied by the Pirs docking compartment — which itself has the Progress MS-16 vehicle docked to it.  

    If Nauka is declared “go” for arrival to the ISS after a successful launch and initial orbital checkout over July 21 and 22, the Progress MS-16 vehicle will remove the Pirs module from the Zvezda nadir docking port on Friday, July 23 at 13:17 UTC / 09:17 EDT to make room for Nauka.

    Pirs will not be removed from the Station until Nauka receives post-launch clearance to proceed with its mission as Pirs is a critical docking port and module for the ISS until Nauka is ready to take its place.  Nevertheless, Pirs will not be brought back to the ISS but will instead remain gripped by Progress MS-16 as the craft deorbits for a destructive reentry into Earth’s atmosphere — making Pirs the first ISS module to be decommissioned and removed from the outpost.  

    Six days after Pirs’ permanent departure, Nauka is scheduled to perform the final rendezvous sequence with the ISS and dock itself to the Zvezda service module’s nadir location on July 29 at 13:25 UTC / 09:25 EDT.

    (Lead image: A Proton-M ignites its engine ahead of liftoff from Baikonur Site 200/39. Credit: Roscosmos)

    The post Nauka science module’s launch to ISS arrives appeared first on NASASpaceFlight.com.

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