SpaceX’s Dragon capsule for resupply mission CRS-13 has arrived at the International Space Station on Sunday for the second time in its career, bringing with it 4,861 lbs of supplies – the largest percentage of which are scientific experiments that will add to the Station’s current list of 329 active scientific investigations.
CRS-13 Dragon – The Arrival:
Astronauts Mark Vande Hei and Joe Acaba used the station’s CanadArm2 arm to capture the spacecraft and maneuver it to the nadir – Earth-side – port of the Harmony module where it will be berthed until January.
Launched by Falcon 9 (B1035.2) from a returning SLC-40 at Cape Canaveral, Dragon has enjoyed an issue-free orbital trip to the ISS.
Cruising to orbit, the SpX-13 Dragon slipped into her preliminary orbit Dragon performed a series of trajectory adjustment burns over the capsule’s slightly less than two-day chase with the ISS to properly align itself 6 km from the Station on Sunday morning for final approach operations.
Those operations are a set of objectives that involve both NASA and SpaceX controllers working towards the eventual arrival at the orbital outpost.
This opens with SpaceX controllers commanding Dragon to begin its final approach sequence with the HA4 Approach Initiation burn, at which time the ISS crew begin actively monitoring Dragon’s approach to the orbital outpost.
During final approach, Dragon maintains proper alignment with the ISS through its Relative Navigation System – which was developed by SpaceX and debuted on CRS-3’s approach on 20 April 2014.
Specifically, the HA4 burn is designed to pulse Dragon up toward the ISS to its 350 m (1,148.3 ft) hold point.
Dragon initially approaches the Station from behind and underneath, and the HA4 burn starts the craft’s trip up the Radial velocity vector, or R-bar, toward the ISS.
Once Dragon arrived at the 350 m hold point, the craft fired its thrusters to hold relative position with the Station – at which time controllers at SpaceX’s Mission Control Center (MCC-X) in Hawthorne, CA, commanded Dragon to perform a 180° Yaw maneuver so the craft was oriented to its proper position for grappling by the Space Station Remote Manipulator System (SSRMS, or Station Arm) at the end of the approach sequence.
After the yaw maneuver, MCC-X and MCC Houston (MCC-H) controllers confirmed the health of Dragon’s systems, after which the spacecraft departed the 350 m hold point.
The next hold point for Dragon is 250 m (820.2 ft) below the ISS. Here, controllers once again confirmed Dragon’s health and the craft’s orientation before giving a “go” to press ahead toward capture.
Importantly, at any point – at a scheduled hold point or otherwise – ground controllers and the Station crew have the ability to manually abort Dragon’s approach through the Commercial Orbital Transportation Services Ultra High-Frequency Communication Unit (CUCU) if an off-nominal condition presents itself.
Dragon’s onboard computers also have the ability to abort the approach sequence at any point if they sense an off-nominal situation – be that drifting off course or a misalignment/miscommunication of the guidance and navigation systems.
These off nominal situations are exceedingly rare, but can/do happen. The SpX-10/CRS-10 Dragon suffered just such a fate on its first attempt at rendezvous in February 2017; berthing was aborted that day and proceeded nominally the following day.
With all going to plan, a “go” to proceed from the 250 m hold point was given by both MCC-X and MCC-H, allowing Dragon to continue its approach.
Shortly thereafter, Dragon crossed the 200 m mark from ISS and entered the Keep Out Sphere (KOS) around the Station.
At this point, MCC-X handed off primary ground control/decision making to NASA controllers at MCC-H.
Dragon then arrived at the 30 m (98.4 ft) hold point where teams performed final assessments of Dragon’s readiness to close to the Capture Point 10 m (32.8 ft) below the ISS.
Once Dragon arrived at the Capture Point, Mark Vande Hei and Joe Acaba – working in the Robotic Work Station in the Cupola lab – extended the SSRMS toward Dragon’s grapple fixture.
After receiving a “Go for Capture” from MCC-H, the duo used the SSRMS’s camera on the Latching End Effector (as overviewed in a detailed presentation available in L2) to precisely move the Station Arm to grapple posture.
At this point, they inhibited the Station’s thrusters and Dragon was commanded to “free drift” mode.
Then the SSRMS moved over Dragon’s grapple fixture pin and triggered the capture sequence.
After capture, a series of post-grapple checkouts occur before Dragon is carefully translated to its pre-install position 3.5 m away from Node-2 Harmony’s nadir port.
Once at the pre-install position, Station crewmembers will take photos and videos of Dragon for post-launch engineering evaluation.
Then Dragon will be moved 1.5 m from Node-2, at which point they will wait for the final “go for berthing” call to connect Dragon to the Common Berthing Mechanism (CBM) interface and secure the spacecraft to the Station.
CRS-13 Dragon – Delivering the science:
For the second time, the same Dragon spacecraft has arrived at the ISS twice, with CRS-13’s Dragon having previously been used for the CRS-6 mission in 2015.
This marks the second time this year the Station has welcomed a previously flown Dragon; the first SpaceX CRS (Commercial Resupply Services) flight to reuse a Dragon was CRS-11 in June of this year using the Dragon that flew CRS-4 in 2014.
In all, CRS-13 is delivering 4,861 lbs (2,205 kg) of cargo to the ISS: 1,080 lbs (490 kg) of Crew Supplies; 1,567 lbs (711 kg) of Science Investigations; 363 lbs (165 kg) of EVA Equipment; 416 lbs (189 kg) of Vehicle Hardware; 11 lbs (5 kg) of Computer Resources; and 1,422 lbs (645 kg) of unpressurized, external cargo in Dragon’s trunk.
Of the science payloads launching to Station, two are external experiments: Total and Spectral Solar Irradiance Sensor (TSIS-1) and the Space Debris Sensor.
Solar irradiance is one of the longest and most fundamental of all climate data records derived from space-based observations.
TSIS-1 is a dual-instrument package that will acquire solar irradiance measurements from the International Space Station for five years and will provide critical data in determining the natural forcing of the climate system and will ensure the continuity of the solar irradiance climate data record.
TSIS-1 will be mounted outside the Space Station on one of the Express Logistics Carriers (ELCs) that were brought to the Station by the Shuttles in the latter part of the construction effort for the ISS.
The instrument will track the sun just like the Station’s solar arrays do and will provide the most accurate measurements to date of the spectral solar irradiance and establish Earth’s total energy input while understanding how Earth’s atmosphere responds to changes in the sun’s output.
The experiment will provide three times less uncertainty for total spectral irradiance than current measurements.
The primary mission TSIS-1 mission is slated to last five years with an option to extend for an additional two years.
Also to be mounted outside the Station is the Space Debris Sensor, or SDS.
SDS will be mounted outside the Columbus laboratory and is a calibrated impact sensor that will monitor impacts caused by small-scale space debris for a period of two to three years.
The sensor records the time and scale of impacts from relatively small space particles using dual-layer thin films, an acoustic sensor system, a resistive grid sensor system, and a sensored-embedded backstop.
Data provided by the SDS will help improve ISS safety by monitoring the risks and generating more accurate estimates of how much small-scale debris exists in space.
The limiting life factor for SDS is the damage it will take from impacts. While two to three years is the anticipated lifetime of the experiment, it has been built to operate up to five years.
In addition to these two external experiments, numerous internal scientific investigations have also now arrived at the International Space Station via Dragon, including: Assessing Osteoblast Response to Tetranite, Barley Germination and Malting in Microgravity, Implantable Nanochannel System for Delivery of Therapeutics for Muscle Atrophy (Rodent Research-6), and Biorasis Glucose Biosensor.
The Assessing Osteoblast Response to Tetranite experiment will examine the cellular response to a new type of bone adhesive in a microgravity environment.
This experiment will grow bone cells in the presence of a commercially available bone adhesive, and a new product called Tetranite. Sets of bone cell cultures grow with the different adhesives for 20 days and are then fixed, frozen, and returned to Earth for detailed analysis in a fully equipped biological laboratory.
The goal of this investigation is to explore the ability of Tetranite, a synthetic bone material capable of adhering bone to metal within minutes, to accelerate bone repair.
It is well known that microgravity affects bone cell growth and healing, mimicking the symptoms observed in osteoporosis. This investigation will seek to evaluate the response of osteoblasts (a bone cell subtype responsible for renewing bones) to Tetranite.
Understanding bone cell-Tetranite interactions could provide insight into the post-fracture bone healing response and assist in the development of more effective treatments for patients with osteoporosis.
Meanwhile, the Germination of ABI Voyager Barley Seeds in Microgravity experiment will evaluate the effects of microgravity on dry seeds, germination, and initial growth of Hordeum vulgare L. (barley).
The dry barley seeds are evaluated during post-flight growth to examine exposure effects on seeds while the seedlings grown in microgravity are evaluated for genetic alterations and morphological abnormalities.
Specifically, this project will explore the effects of spaceflight on the germination of strains of barley, an important food crop.
Observing changes in gene expression and germination after exposure to microgravity will contribute to knowledge of how different plants of the same species that possess genetic differences are better prepared to handle Earth-based stress, such as temperature extremes or water scarcity.
Additionally, the Rodent Research-6 (RR-6) mission will use mice flown aboard the Station as well as a set of mice on Earth to test a drug delivery system for combatting muscular breakdown (atrophy) in space or during period of muscle inactivity (disuse conditions).
RR-6 includes groups of mice selectively treated with a placebo or implanted with a nanochannel drug delivery chip that administers compounds meant to maintain muscle in low gravity/disuse conditions.
Two groups of 20 mice will live aboard the ISS in the rodent habitat for durations of one and two months.
This experiment is specifically studying an implantable drug delivery system that circumvents the need for daily injections. The drug formoterol, used in the management of asthma and other medical conditions, will be administered by controlled release from a nanochannel implant to achieve a constant and reliable dosage.
If successful, this system could serve as a more reliable and accurate technology for drug delivery. Moreover, this validated system may rapidly translate into a commercial product.
Sarcopenia, or muscle wasting, is a condition that affects more than 50% of the geriatric population; however, therapeutics used to treat this condition are limited to physical activity or generic hormones.
The most commonly used pharmaceutical intervention for sarcopenia is formoterol, but administering these drugs requires a daily injection, which can be inconvenient.
This will test plans to develop an implantable device that will safely administer formoterol over a long period of time without patients needing a daily injection, something that could greatly improve quality of life.
Finally – but not the last of the experiments that have now arrived on Station is the Biorasis Glucose Biosensor.
This experiment will evaluate the accuracy of a medically implantable glucose biosensor, Glucowizzard, for day-to-day diabetes management.
Currently, glucose transport to the sensing site of a biosensor can take up to 20 minutes, a delay that complicates achieving tight glycemic control, and can lead to serious complications for diabetics.
Microgravity makes it possible to isolate and monitor the glucose diffusion factor, which could lead to improvements in the accuracy of the sensor.
Presently, the World Health Organization projects that the global diabetic population will reach 366 million by 2030. In order to prevent serious health problems, many people with diabetes currently use glucose biosensors that may inaccurately measure their glucose levels prior to self-administering insulin. This experiment seeks a way to curtail that issue.
(Images: NASA, CASIS, Brady Kennison for NASASpaceFlight and Nathan Koga NSF L2 Renders of Dragon near the ISS)