NASA evaluate rescue plans for Orion crew after off-nominal landing
NASA teams are continuing to set up the mission rules for their Orion spacecraft, with the latest set of expansive “Concept of Operations (CONOPS)” outlines including scenarios for keeping a crew alive after they have splashed down at the end of a mission. The scenarios include off-nominal landings, where a crew may require rescue from remote areas of the ocean by Department of Defence (DoD) assets.
Off Nominal Landings:
For the 30 years of the Space Shuttle Program (SSP), NASA crews returned to one of three landing sites, mainly the Kennedy Space Center (KSC), with the alternative of Edwards Air Force Base in California, and once at White Sands in New Mexico (STS-3).
Their pinpoint runway landing was facilitated by the Shuttle orbiters completing their missions by utilizing their cross-range ability to land like an airplane – or glider to be more precise – prior to the crew egressing on to the tarmac and into the care of landing crews.
While it was never required during the history of the SSP, a vast amount of emergency landing options – likely to have been utilized in the event of a call from Mission Control to return to Earth “immediately”, as nearly conducted on STS-109 with Columbia - were also available, with a huge database, using the Google Earth program, providing full details of literally 1000s of runways across the planet.
This massive Emergency Landing Site (ELS) database (See L2 link here to download this database into Google Earth) lists of every possible runway in the world – at least between 57 deg N and 57 deg S – where the shuttle might possibly make an emergency landing, with the Landing Support Officer (LSO) team color coding every runway in rank of ability for an orbiter to stand a chance of landing and coming to a stop.
As explained by former Space Shuttle Program manager Wayne Hale on the L2 ELS database download section, the Mission Operations Directorate (MOD) briefed the teams at least once a year on what to do if a shuttle was forced to make an emergency landing – such as the basic requirements for a 1,200 feet exclusion zone while the crew powered down the orbiter, prior to the arrival of the NASA rapid response team within 24 hours.
However, the list went beyond just the long runways with active towers and on scene fire/crash rescue capability, explaining why thousands of runways are listed and ranked in the database.
The database was in addition to a specific handbook the crew flew with, known as the SSP Approved Landing Sites Maps and Charts (See L2 Link to download the pdf) – listing around 50 runways across the planet, with expansive details, approach photographs and navigation aids.
That list included the CONUS sites, the TransAtlantic Abort Landing (TAL) runways, through to the rather “sporty” – yet sometimes scenic – strips, such as the HAO Atoll, Tuamotu Islands, in French Polynesia.
For Orion, a return to the old days of water landings will change the rules once again, as much as Orion was originally designed to return to land via an airbag-assisted touchdown – not unlike Boeing’s CST-100 spacecraft. SpaceX’s Dragon, meanwhile, is aiming for a Draco thruster-assisted return to land when it begins crewed missions.
With a focus on keeping the crew safe during the period of time they will have to wait for recovery forces to arrive, the landing considerations for Orion range from pad aborts through to off-nominal landings around the world.
While highly undesirable, the pad abort would result in the crew splashing down just off the coastline from where they were expecting to start their mission. For this scenario the crew would be rescued within minutes, via crews already stationed at Patrick Air Force Base and at the Shuttle Landing Facility (SLF).
Ascent Abort scenarios would result in several potential splashdown points, depending on the time the abort was called during the ride uphill, and if the emergency came after the Launch Abort System (LAS) had been jettisoned.
With the LAS remaining with the vehicle during all of the first stage and part of the second stage ascent, an abort could result in the Orion splashing down up to 300 miles downrange of the launch pad, according to the expansive and updated Orion CONOPS presentation (available on L2 – LINK).
A later abort would result in a choice between aborting to orbit and what is called an Untargetted Abort Splashdown (UAS) – the latter avoiding the use of the Service Module propulsion subsystem for extending the downrange. Such a UAS abort would result in an Orion splashdown in the Atlantic or Indian Ocean.
Providing the Orion’s propulsion systems are in good shape, Abort To Orbit (ATO) would require use of the Orion Main Engine (OME) and auxiliary thrusters to allow controllers on the ground to decide between continuing with the mission, changing the mission objectives, or requesting a return to Earth.
Notably, the document adds that the crew have an option to override an abort command, if Orion’s Abort Decision Logic (ADL) informs the crew it wishes to conduct what is described as a Mode 1 abort – using the LAS. If the crew take no action, the abort is initiated automatically.
Mode codes for the other abort options, through to Mode 4 for Abort To Orbit (ATO) also exist, while it is noted the reasons for taking the abort option are not exclusive to hardware issues, such as a propulsion problem with the Space Launch System (SLS) tasked with lofting Orion into space. Other examples – such as a health emergency with a crewmember during launch itself – are cited in the document.
For all splashdown options, including the end of a nominal mission, Orion will provide its final role by protecting the crew on the ocean surface.
With the crew expected to be in communication with Mission Control back in Houston via S-Band, controllers will be in charge of informing the recovery forces of the expected splashdown area.
Meanwhile, with Orion hitting the ocean surface, an automated sequence will take place, including the cutting of the main parachutes, followed by the activation the CM Uprighting System (CMUS). The latter can be initiated by the crew in the event the parachute risers interfere with the automated CMUS sequence. Such a scenario is called a Stable-2 condition, with the crew safe in their seat restraints, but “face down” inside the module.
CMUS is also required to correct Orion’s position to avoid the antennas from being underwater, which would cause a communication blackout with MCC.
With a beacon – also containing a GPS signal – deployed, the crew would then begin to power down the Orion, a procedure estimated to take 15 minutes.
The crew are expected to receive cooling for two hours after initial power down, a key period of time for all landing scenarios. This cooling system would require shut-down when the recovery forces arrive, in order to provide a safe environment for the Search and Rescue (SAR) team.
Under normal conditions, a US Navy ship would already be in the area, allowing for Orion to be brought into the well deck and secured in the recovery cradle. A team on the ship would then complete the full power-down of Orion while the crew head for medical evaluations.
For off-nominal conditions, such as a splashdown in an area where recovery forces are unable to reach the crew within two hours, use of a snorkel fan would be required, in order to provide the crew with fresh air.
In this scenario, the crew would be required to deactivate the cooling (ammonia) system and power down the vehicle, while donning emergency masks. Once the sensors show there is no ammonia or hydrazine around the vehicle, the crew would be allowed to doff their masks.
In a contingency situation, such as a floatation issue with the Orion, the crew can release the side hatch via the pyrotechnic hatch latch release system. The crew would use Emergency Breathing Apparatus (EBA) and EVA equipment to provide them with the estimated 10 minutes of time required to deploy the life raft.
Providing Orion is in good condition, the vehicle is capable of protecting the crew for a 24 hour period, even in an off-nominal landing condition. As with all splashdown scenarios, the crew would have a satellite phone with them to communicate with Mission Control, who would then coordinate the rescue.
The rescue – according to the CONOPS – would bring an additional focus on Department of Defence (DoD) assets, with plans to have a trained DoD team versed in Orion crew recovery operations, ready to deploy to the splashdown point from the air.
While the rescue ship may require a large amount of time to get to the recovery point, the CONOPS notes small rescue boats would be first on the scene – potentially air-dropped – with additional boats providing supplies and emergency assistance to the crew, while they wait for the large recovery vessel.
Once again, the focus is on the first few hours after splashdown, with the need to provide alternative cooling to the crew after Orion has its systems powered down. Options include the donning of a Liquid Cooling Ventilation Garment (LCVG), after the two hour point.
Although unthinkable, the CONOPS also cover scenarios where the crew can’t be rescued within 24 hours. Orion is capable of keeping the crew safe for longer than the 24 hour period, although several assets – including the satellite phone – would be placed into “duty cycle” to prolong battery life.
Options to egress and await rescue in the life raft are also available, especially in the event the vehicle begins to leak, potentially due to being compromised during entry and landing.
The plans show the crew will have two emergency survival kits on board – for a four person crew – that includes life preservers and life rafts.
The CONOPS appears to have taken lessons learned from a 2008 study into Orion’s ability to keep its crew safe post-splashdown. As reported by this site, managers were concerned about post-36 hour survival requirements, prior to the CONOPS mainly concentrating on the 24 hour rescue requirement.
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