Unofficial Guidelines for EVA on Marsí Surface

As derived from assumptions listed in DRA51

By IonMars

November 10, 2014

Preface

One Saturday I (IonMars) was writing an article about the NASA plan for exploring Mars. This required me to track down the specs for the vehicles and equipment to be employed when and if Congress ever holds hands long enough to commit the money for Mars exploration. I was studying the chapter on Mars Surface Extravehicular Activities (EVAs)1 when I realized (whoa!) this section was written unlike any other.  It was laid out in outline form with lettered headings, numbered subheading and sub-sub headings, like a Federal Regulation.

It was only a long list of assumptions that had gone into the planning study but I realized that if the word “assumption” were changed it would change the whole nature of the specifications. I began to experiment. I changed “assume” to “will” to indicate an engineering design spec that a Mars Pioneer could expect in the vehicle or instrument that had been built for the mission. I changed “assume” to “shall” where the Pioneer will be expected to follow a set of procedures when carrying out the mission. I entered these conversions and some minor editing and voila! It looked just like a formal guideline issued by NASA.

In the absence of specific guidelines from NASA or from SpaceX for the early Mars colonists, we become desperate. We so want to build a Handbook for Colonists that we may even check out a pseudo-guideline as a starting point. This guideline can be useful as a learning tool. It incorporates the intentions of the agency at this time and shows the current status of their conceptual development. So here it is.

The following guidelines (assumptions) are derived from the 2013 update to the Mars Design Reference Architecture 5.0 (DRA5) published in March 2014:

 

Concept of Operations for Mars Surface EVAs

  1. For each exploration excursion, the crew shall spend 2 weeks in the pressurized rover and two 3-hour periods each day on EVAs. The durations of EVAs and consumables usage shall be equivalent to the Mars Mission Surface Phases 2 through 5, DRA5.
  2. Upon landing, up to one week shall be allowed for each crewmember to acclimate to Mars (3/8) gravity.
  3. To initiate an excursion, four crewmembers shall transfer from the habitat/lander into two pressurized rovers. Each pair of crewmembers shall perform exploration EVAs from each rover.
  4. Crewmember pairs shall rotate between the habitat and the rovers every 2 weeks. This assumes back-to-back14-day rover excursions, with rover recharge and crew rotation as necessary at the habitat within this same 14-day period.
  5. Habitat/lander-based crewmembers shall perform up to three 6.5-hour EVAs weekly for habitat maintenance, trash ops, and local exploration.

 

Mission and EVA Guidelines

  1. The total duration of a Mars surface mission will be 500 days.
  2.  The size of crew for each mission will be six members. All crewmembers shall perform EVAs and all surface elements will be EVA-capable, including the habitat /lander and the pressurized rovers. Note that a crew size of 6 vs. 4 crewmembers drives the EVA system architecture, principally consumables and logistics.
  3. There shall be no planned microgravity EVAs during (in-space) transit (such as how Apollo retrieved film canisters on the way back from the moon). Microgravity EVAs will be possible for contingencies.
  4. Mars Surface Mission Phase 2 will allow the crew to adjust to Mars gravity after long duration exposure to a microgravity environment during transit. Crew activities may include limited EVAs to support scientific investigations or to initiate the deployment and activation of surface vehicles and equipment.
  5. Mars surface operations during solar conjunction shall be limited to short EVAs as opposed to long traverses. Direct communications to Earth will be unavailable during solar conjunction. This occurs approximately every 26 Earth months and lasts about 2 Earth weeks.
  6.  During all EVA activities, each EVA crewmember must be able to be physically reached by another crewmember within 45 (to be reviewed) minutes. This could be achieved by two EVA crewmembers in close proximity to an In-Vehicle Activity (IVA) crewmember having the ability for quick egress from habitat or nearby rover.
  7. Crew shall utilize rear-entry EVA suits for extravehicular surface operations.
  8. Nominally, suitports will be used to enter into or egress from the pressurized mobile rovers. The habitat module will include an airlock for EVA ingress/egress.
  9. Umbilical lines shall be employed during depress and repress for EVA. [In-space? IonMars]
  10. Emergency Procedures:

1. The surface habitat/lander and pressurized rovers will accommodate an incapacitated crewmember.

2. In the event of a medical emergency during EVA, the ill crewmember shall be brought inside a habitable volume for treatment while performing proper decontamination and medical protocol as necessary.

3. Habitable volume will accommodate two means of EVA ingress/egress. In case of fire or defective “airlock,” the crew will have a means of entering or exiting. Nominal ingress will be through the airlock; secondary ingress is possible through the rover side hatch or the habitat/lander inner hatch.

3) The habitat will provide a level of care consistent with medical needs on Mars

k. Habitat/Lander Guidelines:

1. Suits will be stored inside the habitat during (in-space) transit.

2. The lander will serve as the surface habitat.

3. The habitat/lander system will provide the primary interface to EVA; an airlock is integrated with the element.

4. The porch on the habitat lander will have a minimum size, dependent on the distance between the hatch and the surface.

5. The airlock will accommodate two suits simultaneously.

6. Mars suit maintenance:

6.1.Maintenance facilities. The habitat/lander will provide a suit maintenance / dust containment area. Post-EVA basic inspection and cleaning operations will be conducted within the pressurized airlock and more extensive maintenance and repair will be conducted in the suit maintenance area.

6.2. Umbilical Interface Panels. The habitat will have two umbilical interface panels located where suited crewmember operations occur.

6.2.1.Recharge capability. The suit recharge capability will include: oxygen (3000 psia), water resupply (potable and cooling), and battery recharge.

6.2.2.Panel service. The umbilical interface panels will provide power, communications (wireless and hardline), and vacuum lines.

6.2.3. Exclusivity. All services will be provided via the Recharge panel (two umbilical connections and two vacuum line connections).

L. Pressurized Rover Guidelines:

1. Two pressurized rovers will be present on the surface.

2. The rover will utilize a suitport to facilitate rapid entry and egress. Note that at the time of the 2013 update, the most mature technology of this airlock type is a suitport.

3. Crewmembers must conduct an initial EVA from the habitat lander to install suits onto the rover suitports.

4. Two crewmembers shall spend 2 weeks in a pressurized rover and then return to the habitat for recharge and suit maintenance, as necessary. Crew rotation will include suit rotation.

5. The pressurized rover will operate at 8.2psia.

6. In the event of a rover failure, the EVA crewmembers must be capable of (TBD) km walk-back. For a "rover-based" EVA, the crew shall not travel from the habitat lander farther than the distance they are able to walk back to the habitat/lander, unless a second rover is available for rescue. With two rovers, each one can travel farther than walk back distance from the habitat, but the two rovers must maintain rescue distance in respect to each other.

            7. The pressurized rovers will accommodate contingency suit maintenance.

m. EVA Hours:

1. Crew Limits for EVA hours:

1.1.Each crew is limited to no more than 12 hours of EVA in a 48-hour period and 24 hours of EVA per 7-day period with at least one full non-EVA day of rest within that same 7-dayperiod.

1.2.EVA limits do not apply to a transfer EVA between the habitat lander and pressurized rover, which may extend the EVA hours for that week to 27 hours.

2. Types of EVAs from the habitat lander:

2.1. Crew shall perform a 3-hour EVA to transfer samples, logistics, and suits when transferring to the pressurized rover in preparation for excursions.

2.2. Crew shall perform up to three 6.5-hour EVAs each week for habitat maintenance, trash ops, local exploration, etc.

3. Types of EVAs from the pressurized rover:

3.1. Crew may perform up to three 1-hour EVAs per day for 6 days per week. [18 EVA hours per week per crewmember]

3.2. Crew may perform up to two 3-hour EVAs per day for up to 4 days per week. Crew may elect to perform a single EVA on a given day and use that EVA time on another day, but must protect at least one day off per week. [24 EVA hours per week per crewmember]

3.3.Crew may perform one 8-hour EVA per day for up to 3 days per week. [24 EVA hours per week per crewmember]

3.4.For hardware cycle life and mass calculations in 2012, the EVA Office (XA) is assuming two 3-hour EVAs per day for up to 4 days per week to generate a MEL (ref 3.2 above). This number may change with further testing and evaluations of the EVA suit and system.

4. Mission Extension: If surface mission duration is extended past 500 days due to contingency, no nominal EVAs are planned.

4.1. Real-time assessments shall be performed to conduct contingency EVAs if needed.

4.2. No additional logistics are provided to support mission extension (next cargo mission could land at same site if needed).

n. EVA Consumable Usage:

1. Amount of O2 use per hour of EVA will be (TBD).

2. Amount of H2O usage per hour of EVA will be (TBD).

3. Amount of consumable for CO2 removal will be (TBD).  If RCA, the amount of sweep gas usage per hour while on EVA will be the same as given in reference n below. Or, the amount of METOX and LiOH cartridges will be (TBD).

o. Martian environment will require the use of a sweep gas or pump with RCA, or other new technology.

p. Ancillary EVA Equipment:

1. Mars missions will require a reusable (waste) bag to reduce launch mass.

2. Current waste containment for an EMU is a MAG, which is disposed after each EVA.

3. EVA equipment bags shall be used during EVAs.

q. EVA System Hardware Logistics:

1. EVA equipment that is size-dependent will launch with the crewmembers. This will include items such as the pressure garment (PGS), gloves, thermal comfort unit (TCU), etc.

2. EVA equipment that is critical for a specific phase of flight will launch with the crewmembers and be accessible during the appropriate flight phase. This will include each crewmember’s prime and backup suit, and his microgravity-specific equipment.

3. EVA equipment that is not size dependent will launch with the pre-deployed cargo, assuming the certified shelf life of each item can withstand the increased mission duration length. This will include items such as spare PLSS, spare helmets, MAGs, batteries, etc.

4. EVA spares stowage is accommodated within the habitable volume of the habitat/lander.

5. Two EVA suits, PGS and PLSS, will be manifested for each crewmember. For a crew size of 6, this totals 12 suits.

6. Suit maintenance will be required every 28 days or (TBD) hours of EVAs.

7. EVA equipment will not return in the Orion capsule.  There will be no allocations for return of EVA equipment for re-use or post-flight analysis. It is desirable to return flown EVA suits to Earth for post-flight analysis purposes with the benefit of influencing improvements in future suit designs.

8. Logistics Quantities: The specified quantities of logistics and spares items will be updated qhen limited life duration is determined through certification.

8.1.The following spares will be flown for a crew size of six: spare PGS (2) and spare PLSS (5). (Reference: for a crew size of 4, the quantities were 2 spare PGS and 3 spare PLSS.)

8.2.The former (lunar) suit plan was to certify the mission for 100 EVAs. The total number of EVA hours will be modified for longer the Mars mission.

8.3.Eleven pairs of EVA gloves will be available per crewmember (prime and spares). For a crew size of six, this totals 66 pairs of gloves.

8.3.1. Due to crew specific sizing and fit, gloves will launch with the crewmembers. Three pairs will be easily accessible during microgravity phases of the mission.

8.3.2. Glove quantities are based on the 162 hours certified for the life of a pair of glove (same as ISS EMU Phase VI glove certification, which has not been realized). It is based on 24 EVA hours/week for a 500-day surface mission.

8.4. Batteries:

8.4.1.Three suit batteries will be provided per crewmember (2 prime, 1 spare) based on the development of new battery chemistry with greater power density than current battery technology.

8.4.2. Un-activated silver zinc batteries may be employed. They would be launched and stowed dry, and then activated when needed on Mars.

8.4.3. Note: current Lithium ion batteries are limited to 5-year life.

8.5. Thirty-six Thermal Comfort Units (TCUs) will be provided per crewmember. For a crew size of six, this totals 216 TCUs. TCU quantity is based on one set of TCUs every 2 weeks and mission duration of 500 days.

r. Protection of Planetary Environment

1. Crews will be allowed to land and operate within certain approved zones where forward contamination is not an issue.

2. EVA suits shall not require sterilization prior to exiting the habitat/lander or pressurized rover. This is based on a sample return mission that verifies “sterilization” of suits is not required prior to entering a pressurized volume.

3. Operational controls for planetary protection will establish keep-out zones to preclude EVA crewmembers from entering, and possibly contaminating special regions.

4. Crew may collect samples in non-special regions using EVA gloves and other EVA tools as needed (consistent with science needs)

5. Trade study will address planetary protection if it becomes a driving issue. The study will assess the type of airlock for the habitat lander that will include planetary protection as a consideration. A “mudroom” incorporated between the airlock and the main pressurized volume may be employed as a “hybrid suitlock”.

 6. Suits may require dust covers (TBD).

s. EVA Tools:

1. Micro-gravity Contingency EVA

1.1. Safety tethers

1.2. Waist tethers

1.3. Equipment tethers

1.4. Basic standard tools, such as a driver and sockets

1.5. Repair tools

2. Tools for Surface Science:

2.1. Rock sample collections device (bag over glove, scoop, etc.)

2.2. Soil sample collection device

2.3. Chip sample device (rotary percussive drill, hammer, etc.)

2.4. Surface sample device

2.5. Core sample device

2.6. Collection bags

2.7. Trenching tool

2.8. Shovel

2.9. Geophysical arrays

eof

 

Reference 

1) Bret G. Drake and Kevin D. Watts (editors) (March 2014) Human Exploration of Mars: Design Reference Architecture 5.0 Addendum #2, National Aeronautics and Space Administration, SP-2009-566-ADD2, Pages 401-403