The International Space Station (ISS) has now entered what will be a challenging new year, which will see access to the station for both crews and cargo tested, in wake of last year’s retirement of the Space Shuttle, the start of new commercial resupply flights, and recent failures of Russian launch vehicles.
ISS cargo deliveries:
The year 2011 was a highly successful year in terms of cargo flights to the ISS, with January’s launch of Japan’s H-II Transfer Vehicle-2 (HTV-2), February’s launch of Europe’s Automated Transfer Vehicle-2 (ATV-2), and the successful launches of Space Shuttle missions STS-133, STS-134 and STS-135, as well as numerous Russian Progress flights.
The delivery and installation of the Permanent Multipurpose Module (PMM) to the ISS on STS-133 in February increased the amount of stowage space available on the station for cargo, which paved the way for STS-135 to deliver a massive stockpile of crew provisions to the station on the final Shuttle mission in July.
The stockpile of crew provisions from STS-135 will enable the station to make it to mid-2012 without any additional deliveries of cargo, and make it to 2013 when supplemented with deliveries of cargo from Europe’s ATV and Japan’s HTV. Thus, successful commercial and non-commercial resupply flights to the ISS are essential in order to maintain a crewed presence on the station throughout 2012.
The late-addition of STS-135 to the Shuttle’s manifest in order to shore up ISS’ supplies is already being seen as an excellent decision, given the delays of commercial resupply flights to the ISS and recent failures of Russian rockets.
Non-commercial cargo vehicles:
This year’s non-commercial cargo vehicle flights to the ISS will see two large deliveries made to the station by both Europe and Japan.
Europe’s ATV-3 spacecraft, named “Edoardo Amaldi”, is currently set to launch to the ISS atop an Ariane V rocket from the Kourou space center in French Guiana, on 9th March, and arrive at the ISS for a docking to the Service Module (AM) Aft port ten days later on 19th March. It is scheduled to undock from the ISS on 27th August.
ATV-3 will carry more “dry” cargo (i.e. internal items) than ATV-2 carried to the station in 2011, due to numerous internal structural modifications that have been made that will allow ATV to carry additional internal payload.
This will mean that less “wet” cargo (i.e. propellants) will be carried by ATV-3, however this will not be of big impact to the ISS since ATV-2 performed four “big boosts” of the ISS in 2011 that boosted the station’s altitude to a mean of around 400km, meaning less reboosts will be needed in future, and thus less requirements for propellants. (L2 Link)
The next large non-commercial delivery of ISS cargo will be via Japan’s HTV-3 spacecraft, currently scheduled to launch on 26th June atop an H-IIB rocket from the Tanegashima space center in Japan, arriving at the ISS five days later for a 1st July rendezvous, capture and berthing.
HTV-3 will depart the ISS on 15th August. The HTV-3 mission was originally scheduled for the first quarter of 2012, but was pushed back to mid-2012 due to delays in hardware processing caused by the Japanese earthquake in 2011.
In additional to bringing a large volume of internal cargo to the station, HTV-3 will also carry two external payloads for the ISS – the Space Communication and Navigation (SCaN) testbed, which will be attached to ExPrESS Logistics Carrier-3 (ELC-3), and the Multi-mission Consolidated Equipment (MCE), a payload for the Japanese Exposed Facility (JEF). (L2 Link)
Five Russian Progress flights to the station are also planned in 2012 – Progress M-14M on 25th January, M-15M on 25th April, M-16M on 25th July, M-17M on 23rd October, and M-18M on 26th December. (L2 Link)
Progress flights, however, will be of particular interest to the ISS Program over the course of 2012 due to the multiple failures of Russian launch vehicles in 2011, including two third stages of Soyuz rockets – a Soyuz-U with Progress M-12M/44P on 24th August, and a Soyuz 2-1b with the Meridian satellite on 23rd December.
However, the Progress M-12M third stage failure was attributed to a problem in the RD-0110 engine, while the third stage failure of Meridian used a newer RD-0124 engine.
If any further Soyuz rockets fail in 2012, it will not only have implications for Progress cargo flights, but also Soyuz crewed flights, which could lead to a de-crewing of the station since the ISS partners now depend on the Soyuz for crewed access to the station.
As such, successful launches of both Progress and Soyuz spacecraft are vital for a continued crewed presence on the ISS throughout 2012.
Commercial cargo vehicles:
This year will also mark the first of two long-awaited commercial cargo vehicles visit the station – SpaceX’s Dragon, and Orbital’s Cygnus.
The first commercial spacecraft to attempt to reach the ISS will be SpaceX’s Dragon, which is currently scheduled to launch on the combined COTS-2/3 (C2/C3) mission atop a Falcon 9 rocket from Launch Complex-40 (LC-40) at Cape Canaveral Air Force Station (CCAFS) on 7th February.
Preliminary timelines show that COTS-2 objectives (rendezvous and communication tests) will be performed the day following launch, with COTS-3 objectives (rendezvous, capture & berthing) being performed two days after launch on 9th February. These timelines, however, are not confirmed at this time.
Following a two week stay at the ISS, during which some non-critical supplies will be transferred to the ISS, Dragon will be unberthed from the ISS on 23rd February, for a re-entry and splashdown off the coast of California. (L2 Link)
While Dragon was originally scheduled to reach the station in 2011, ongoing setbacks from the Progress M-12M launch failure and subsequent ISS crew impacts, ISS hardware and software upgrades, Dragon software testing, and Dragon flight review processes delayed the flight into 2012.
With the successful docking of Soyuz TMA-03M/29S to the ISS on 23rd December, which delivered US astronaut Don Pettit to the station, all crewmembers trained to capture and berth Dragon are now aboard the ISS.
ISS hardware and software upgrades, notably the Enhanced Processor & Integrated Communications (EPIC) and X2_R10 software transition, got underway aboard the ISS last week and will continue throughout this week, so far with success.
Dragon software testing and flight reviews are currently ongoing, as much a big hurdle – deployment of an ORBCOMM secondary payload – has now been removed from the C2/C3 mission so that SpaceX can concentrate on Dragon’s flight to the ISS, and not have to worry about ISS conjunction concerns from the ORBCOMM.
Assuming the C2/C3 mission is a success, SpaceX are schedule to fly at least one more Dragon to the ISS in 2012 as an operational resupply spacecraft.
The next commercial cargo craft to attempt to reach the ISS after Dragon will be Orbital’s Cygnus spacecraft, currently scheduled to launch No Earlier Than (NET) June due to ongoing delays with launch pad readiness. A hot-fire test and a test launch with a dummy payload of Cygnus’ Antares (formerly Taurus II) launch vehicle need to be performed prior to the Cygnus C1 mission.
Since ISS can make it only as far as 2013 without any commercial cargo deliveries (assuming successful deliveries of cargo by non-commercial vehicles), this means that at least one commercial resupply vehicle must successfully reach the ISS in 2012 in order to maintain a crewed presence in 2013.
The margin for failure of this year’s COTS vehicle test flights is tight, with sources noting that even with the stockpiles of supplies from STS-135, ISS will struggle to sustain a failure of any COTS vehicle to reach the station.
As such, retirement of the Space Shuttle and its large up/downmass before an operational commercial resupply capability was available has placed additional risk on the ISS, since test flights of new, and in the case of Orbital, untested launch vehicles and spacecraft are now on the critical path for sustained ISS operations.
Although the commercial vehicles in question have yet to reach the station at the start of the year in which they must become operational, the due diligence displayed thus far by both NASA and its commercial partners enables is an encouraging sign.
While the commercial resupply vehicles have been a long time coming, the end is now in sight for the COTS (Commercial Orbital Transportation Services) development program and the transition to the operational Commercial Resupply Services (CRS) program. Due to both the high risks and high payoffs involved, 2012 is likely to be the make-or-break year for COTS and CRS.
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