LIVE: Soyuz TMA-18 launches towards an over-stowed ISS

by Chris Bergin

NASA astronaut Tracy Caldwell Dyson and Russian cosmonauts Alexander Skvortsov and Mikhail Kornienko have launched on their Soyuz TMA-18 vehicle at 10:04 am local time from the Baikonur Cosmodrome in Kazakhstan. The trio will arrive at the International Space Station (ISS) a day before STS-131 launches, with Discovery providing a vast amount of supplies, and also her unique – and much-needed – downmass ability.

Soyuz TMA-18:

The launch vehicle lofting the Soyuz TMA-18 into orbit is the Soyuz-FG. The vehicle was introduced in 1966, deriving from the Vostok launcher, which in turn was based on the 8K74 or R-7 intercontinental ballistic missile. It has become the world’s most used space launcher, flying over 850 times.

The four boosters on the first stage are arranged around the central core and are tapered cylinders with the oxidizer tank in the tapered portion and the kerosene tank in the cylindrical portion. As in the entire Soyuz lower composite, the RD-107A engines of the boosters are powered by nontoxic liquid oxygen – kerosene propellants.

These spark ignition engines are fed by a turbopump running off gases generated by the catalytic decomposition of H2O2 in a gas generator. Each RD-107A has four combustion chambers and nozzles. Liquid nitrogen is used for pressurization of the propellant tanks.

Attitude control is carried out through two movable vernier thrusters and one aerofin. Three-axis flight control is made possible through these eight engines (two per booster) and four aerofins (one per booster). The boosters burn for 118 seconds and are then discarded.

Thrust is transferred through a ball joint located at the top of the cone-shaped structure of the booster, which is attached to the central core by two rear struts.

The second stage – or Core Stage – is similar in construction to the booster stages, using the RD-108A engine and four vernier thrusters for three-axis flight control. The core stage nominally burns for 290 seconds. The stage is shaped to accommodate the boosters, and a stiffening ring is located at the upper interface between the boosters and central core.

The boosters and the central core are ignited on the ground. They burn at intermediate thrust levels for approximately 20 seconds before actual liftoff in order to verify their health and nominal level of operation. The core stage continues to function after booster shutdown and separation.

Ignition of the third stage’s single main engine occurs approximately two seconds before shutdown of the central core. The separation of the stages takes place at a predetermined velocity. After separation, the lower skirt of the third stage is jettisoned in three sections. The third stage of the Soyuz is powered by the RD-0110 engine.

The third-stage engine is powered by a single turbopump spun by gas from combustion of the main propellants in a gas generator. These combustion gases are recovered to feed four vernier thrusters that handle attitude control of the vehicle. For deorbitation and collision avoidance, a reaction nozzle is positioned on the side of the stage and vents the oxygen tank.

The LOX tank is pressurized by the heating and evaporation of the oxygen, while the kerosene tank is pressurized by combustion products from the gas generator. An interstage truss structure connects the core stage with the third stage, thereby allowing for the ignition of the third stage before separation of the second. In fact, this ignition assists the separation of the second stage.

The Soyuz Vehicle the crew are riding on consists of three modules: the Orbital Module, the Descent Module (DM), and the Instrumentation/Propulsion Module (IPM). The DM is the only module that returns to Earth, after all three modules nominally separate simultaneously, shortly after the deorbit burn is completed.

The launch comes shortly after Expedition 22 came to a close with the safe landing of Jeff Williams and Maxim Suraev on March 18. The pair were aboard the ISS for five and half months including addition of the “Tranquility” Node 3 and the Cupola.

The station now is tended by Expedition 23 Commander Oleg Kotov and Flight Engineers Soichi Noguchi and T.J. Creamer (indirect crew handover). The three-member crew will expand back to six with the arrival of Soyuz TMA-18.

ISS Status:

Onboard the station, Kotov, Noguchi, and Creamer are busy at work preparing for STS-131, Discovery, scheduled to dock April 7. The trio have work working on the Carbon Dioxide Removal Assembly (CDRA) during this week.

“An IFM (In Flight Maintenance) effort was successfully performed on the last week to bypass a malfunctioning heating sensor. CDRA performance is nominal with two of the three temperature sensors operating,” noted MOD’s April 1 8th Floor News (L2).

“The Water Processing Assembly (WPA) is currently down – a rack rotation is in the plan to continue to investigate potential leaks specifically within the catalytic reactor ORU (Orbital Replacement Unit).”

The importance of Discovery’s downmass capability will also come into play, due to the over-stow situation onboard the ISS.

“ISS is in an over-stow configuration again, and are trying to get as much off the flight as they can. They have come in late with an additional 400 lbs. of mass that they want to bring back on,” noted Flight Operations & Integration on the latest Shuttle Standup/Integration report (L2).

“That is above the heavy weight VLA (Verification Loads Assessment) case. That is being assessed. A schedule shows a complete FD8, which FO&I will try to push on to make it work to support the transfer ops. Most of the loads analysis work will be done by CMC. If it does not work out, we will stow as we are supposed to stow, but we will try to make it work.”

Other notes of interest for the ISS came via the expansive Space Station Program Control Board (SSPCB) notes (L2), which included items such as the removal of Emergency Lighting Power Supplies (ELPS) and implementation of ISS Photo-luminescent Emergency Egress Guidance System (EEGS).

“This CR (Change Request) changes the requirements document to state emergency lighting on ISS can be provided by illumination vs. lighting – making the application of glow-in-the-dark stickers applicable for finding hatchways in a dark ISS,” outlined the 8th Floor News.

“EELS requirement was to mark exits in darkness, not have anything to do for fire/smoke viewing. There is no requirement for illumination or amount of visibility from smoke. A part of the discussion was over the cost of sustaining a lighting system on ISS vs. stickers.

“ISS decided to fly and install the EEGS stickers. The failure mode on ISS is for lights out only, not smoke/visual obscuration. Fire has nothing to do with loss of lights. Crew should take a flashlight in when they do fire response and get to the point where we turn off lights.”

Additional payload requests for downstream shuttle flights were also noted, such as a request for New Spare Orbital Replacement Unit (ORU) deliveries on what is currently the final mission on the shuttle manifest, STS-133.

“Build, Test and Deliver New Upper and Lower Multiplexer Demultiplexer (MDM) Assemblies for Removal and Replacement (R&R) Support in the Photovoltaic Controller Unit (PCVU) Installations. There are no spare PVCU MDMs available on-orbit – also need new brackets as long-lead items that can make ULF5.

“PVCU MDMs attach to a bracket (bracket is the structural attachment). Driving screw on bracket mates blind connectors on the back of the MDM. There are both lower brackets and upper brackets for both configurations of the PVCU MDMs. This CR is only for a lower bracket (have upper from previous CR) and second PVCU MDM. Approved to build and fly for ULF5.”

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