Inflatable Module Habitat BA-330. Credit: Bigelow Aerospace
In-Space Habitat Concept near the Earth's Moon orbit.
NASA (NIAC) - TURBOLIFT + Lockheed-Martin MARS BASE CAMP
The Turbolift Hybrid Artificial Gravity concept proposed by IMSG Laboratories Inc. and selected for NASA Innovative Advanced Concepts (NIAC) Phase I study. Video: 2017 Perry Papadopoulos. Credit: f r a g o m a t i k
ARTIFICIAL GRAVITY - TURBOLIFT
A new artificial gravity concept could help astronauts endure long duration missions in the near-weightless environment of space.
NASA 360 takes a look at the NASA Innovative Advanced Concept (NIAC) known as Turbolift, a new approach to artificial gravity. To watch the in-depth presentation about this topic please visit: http://bit.ly/2ACdz0o This video represents a research study within the NASA Innovative Advanced Concepts (NIAC) program. NIAC is a visionary and far-reaching aerospace program, one that has the potential to create breakthrough technologies for possible future space missions.
However, such early stage technology developments may never become actual NASA missions. For more information about NIAC, visit: www.nasa.gov/niac. Credit: NASA 360
The TURBOLIFT is a Linear Sled Hybrid Artificial Gravity concept (LSH AG) thatcould be essential to enabling crewed long-duration lunar stays, cis-lunar exploration, Mars orbital missions, exploration of Martian moons, Martian landings, or any further destination in our solar system.
The LSH AG system could broadly prove beneficial for any long-duration space exploration mission.
In the near future, this system could be applicable to crewed missions to Mars. There, humans will be exposed at more than 1 year in microgravity and/or potentially ~2 years on the surface with about 0.38 of gravity.
Long-duration exposure to microgravity leads to bone loss, muscle atrophy, cardiovascular deconditioning, and visual degradation. During gravity transitions astronauts experience sensorimotor impairment. These deleterious effects threaten astronaut safety, performance, and long-term well-being.
Various countermeasures have been employed for mitigating these effects, such as exercise, pharmaceuticals, diet, and fluid loading. However, these approaches treat individual symptoms – each physiological system is addressed with primarily one countermeasure. Furthermore, the current suite of countermeasures has been only partially effective and may be insufficient for longer duration, exploration missions. An alternative is artificial gravity (AG), which promises to be a holistic, comprehensive countermeasure.
Linear Sled Hybrid AG Concept
Figure 1: Linear Sled Hybrid AG system - from left to right the rider accelerates to produce footward loading, does a half rotation, then decelerates also producing footward loading and then the sequence repeats.
As an alternative AG design, they propose a linear sled “hybrid” system, shown in Figure 1. Here, the AG is produced primarily through “pure” linear acceleration. A brief acceleration phase creates foot ward gravitational loading, shifting body fluid toward the rider’s feet and providing weight bearing to the legs/feet, as if the rider were standing on Earth. Then the astronaut is quickly rotated 180° to reorient the rider, during which he/she continues to translate at a constant linear velocity. Next the rider is linearly decelerated, again creating foot ward gravitational loading. The astronaut is then accelerated back in the opposite direction, repeating the sequence. Between the acceleration/deceleration phases and rotation phase, they have accounted for transition phases in which the rider only linearly translates at a constant velocity.
During the acceleration and deceleration phases, uniform gravitational loading (e.g., 1 Earth G) will be applied across the entire body (no gravity gradient). Furthermore, as there is no rotation, there will presumably not be any vestibular cross-coupled illusion or Coriolis forces. In this sense, the linear acceleration and deceleration of the LSH provides a “pure” form of AG.
During the 180° rotation, there will also be AG loading due to centripetal acceleration, hence the “hybrid” aspect of combining linear and centripetal acceleration. We envision the rotation occurring about an axis located at the rider’s head (though other configurations are feasible). This has the advantage of simplifying the motion stimulation to the vestibular system, located in the rider’s head. It also causes the loading from the centripetal acceleration to be exclusively foot ward.
space MEDICal BACKGROUND
US SKYLAB STATION
RUSSIAN MIR STATION
In such historical missions of extended duration into the U.S. Skylab, the Russian Mir Stations, as well as the ISS, extensive biomedical studies has been, and are, undertaken. Their findings that periodic physical exercise, as running, is imperative for the maintenance of health of astronauts.
In such environment of zero-gravity, bodily fluids are redistributed, with less in the lower extremities and more in the upper body. Also, the height increases and the body mass usually decreases with a loss of muscular tissue. The veins and arteries of the legs become weaker and, anemia occurs, accompanied by a significant reduction in blood count. When they return to Earth, a feeling of weakness and the loss of a sense of balance are experienced.
The Astronaut recoveries from all these effects is relatively rapid and is nearly complete after only a week or so. However, a serious cause for concern is the loss of bone calcium that increases with the length of a mission and shows no sign of cessation.
The possibility of irreparable deterioration on future space missions of long duration points to a need for artificial gravity. The use of centrifugal force in a suitably designed rotating space vehicle is an obvious way of simulating gravity, as well as the Turbolift system.
ENVIRONMENTAL CONTROL AND LIFE SUPPORT SYSTEMS (ECLSS)
One of the challenges of the pressurized pod concept, is that the pod itself will need to provide Environmental Control and Life Support System (ECLSS) functionality during operation when a rider is inside. Estimates for the ECLSS requirements are shown in Table 7, based upon an 85 kg male (NASA Life Support Baseline Values and Assumptions Document (BVAD), 2015).
DESIGN OF A PRESSURIZED POD
The rider be enclosed in a fairly small pressurized pod that then experiences the LSH motion profile (Figure 10). The approach is similar to the “Single Person Spacecraft” concept proposed by NASA engineers at Huntsville, except here the pressurized pod is not maneuverable beyond the LSH motion profile. The “pod” concept has the tremendous advantage of reducing the required pressurized volume to that just large enough to house a single rider comfortably (e.g., similar to a phone booth or small shower).
As the pressurized pod translates on the LSH track, it would need to be disconnected and sealed off from the primary pressurized vehicle/habitat during operation.
Habitable Volume of Pod
As a preliminary estimate, we quantified the habitable volume of the pressurized pod to be equal to that of the sleeping quarters in the ISS. As we desire for the center of rotation of the pod to be aligned with the rider’s eye/ear location, there is an adjustable footplate to maintain positioning for astronauts of different heights. The pod also has a counter weight arm to help with rotation. The approximate dimensions of the pod concept are shown in Figure 11.
Future analysis will aim to assess the structural integrity of the pod and the required thickness of the walls given the pressures applied to its interior (Figure 12). For now, we assume the structure of the pressurized pod to be aluminum, allow with a thickness of 0.12m, based upon that used for the thickness of the pressurized hull of the ISS.
We note that the loading during the 180° rotation would have a gravity gradient. There would be no centripetal acceleration at the rider’s head (radius of rotation=0), but there would be substantial loading at their feet (radius ≈ height of rider).
Similarly, there would be Coriolis forces if the rider moves his/her limbs, particularly during the peak of the rotation. However, one would not expect any vestibular cross-coupled illusion if the rider makes head movements, even during the rotation, because the rotation is not sustained like on a centrifuge. Lastly, we note that during the beginning and ending of the 180° rotation, where there is angular acceleration/deceleration, lower portions of the rider’s body would experience tangential accelerations which would be perpendicular to the rider’s longitudinal axis.
In summary, the LSH AG system will provide longitudinal, foot ward loading to the astronaut rider’s body while in space. This is expected to mitigate the physiological deconditioning that occurs in microgravity by replicating the gravity loading here on Earth.
There are two important temporal aspects to the LSH system that should be noted. First, we envision astronauts to not be continuously exposed (i.e., 24 hours per day) to the repeated LSH motion sequence. Instead, each astronaut may ride on the LSH system on the order of 1 hour per day (experiencing hundreds to a few thousand repeated motion sequences depending upon the duration of each sequence). This is typically referred to as “intermittent” AG.
Second, the LSH has another, much faster temporal aspect in that the loading changes during each phase (acceleration, transition, rotation, transition, deceleration). We refer to this as the “duty cycle” of the LSH AG system to capture the higher frequency, repeated sequence of the loading profile.
LSH MOTION PROFILE
Longer durations for the linear acceleration and deceleration phases would provide a higher duty cycle, and thus a closer replication of the continuous loading experienced here on Earth. Thus, to mitigate astronaut physiological deconditioning, it would be preferable to have longer duration acceleration and deceleration phases, very short or no transition phases, and a relatively short rotation phase.
However, from an engineering design standpoint, presumably a shorter track length would be preferable to reduce mass and thus cost. From this perspective, shorter durations for all phases are preferred.
This is particularly critical for the acceleration/deceleration phases, in which longer durations not only increase the track length associated with those phases, but lead to a higher linear translation velocity for the transition and rotation phases which further extends the required total track length.
Finally, we consider what may be tolerable for the human riders. Presumably, any duration of acceleration/deceleration would be tolerable as humans regularly experience continuous G-loading just standing on Earth, as well as very brief G-loading.
This lower G-level may or may not be sufficient for maintenance of musculoskeletal or other physiological systems, but is conceptually appropriate for the neuro-vestibular/sensorimotor system, in which prior exposure to a novel environment is typically beneficial (though we note that 0.38 G with a duty cycle does not perfectly mimic continuous 0.38 G, like on the Martian surface).