SpaceX Falcon 9 Full Thrust - CRS-13 - Launching December 15, 2017
Screenshot of CRS-13 with Tim Dodd as host
Mission Rundown: SpaceX Falcon 9 FT - CRS-13
Written: January 22, 2021
My turn to feel the burn
SpaceX will be launching a reused Dragon Capsule C108-2 heading to the International Space Station on top of a reused Falcon 9 booster B1035-2 for a historic set of firsts. This is the first time NASA as a customer will be using a previously flown booster from SpaceX and this is also the first launch from SLC-40, the launch pad that was destroyed during an anomaly on the pad, September 1, 2016.
The first stage booster supported CRS-11 in June, and it will be landing back at LZ-1 at Cape Canaveral Air Force Station. SpaceX is also reusing the Dragon Capsule from this mission, which first flew way back in 2015 for mission CRS-6. The payload this time weighs a mere 2 205 kg.
The Dragon Payload
NASA has contracted for the CRS-13 mission from SpaceX and therefore determines the primary payload, date/time of launch, and orbital parameters for the Dragon space capsule. CRS-13 carried a total of 2,205 kg (4,861 lb) of material into orbit.
This includes 1,560 kg (3,439 lb) of pressurized cargo with packaging bound for the International Space Station, and 645 kg (1,422 lb) of unpressurised cargo composed of two external station experiments: the Total and Spectral Solar Irradiance Sensor (TSIS) and the Space Debris Sensor (SDS).
In early 2015, NASA awarded a contract extension to SpaceX for three CRS additional missions (CRS-13 to CRS-15). As of June 2016, a NASA Inspector General report had this mission manifested for September 2017.
The flight has been delayed from 13 September, 1 November, 4 December, 12 December, and 13 December 2017. SpaceX pushed off the launch to 15 December due to the detection of particulates in the second stage fuel system, taking the time to completely flush out the fuel and liquid oxygen tanks on the first and second stages as a precautionary measure.
The CRS-13 mission launched aboard a Falcon 9 Full Thrust rocket on 15 December 2017 at 15:36:09 UTC from the Cape Canaveral Air Force Station Space Launch Complex 40. The Dragon spacecraft rendezvoused with the International Space Station on 17 December 2017; the vehicle was captured by the Canadarm2 at 10:57 UTC and was berthed to the Harmony module's nadir docking port at 13:26 UTC.
Dragon spent just under a month at the ISS: it was unberthed on 12 January 2018 at 10:47 UTC and was released from Canadarm2 on 13 January 2018 at 09:58 UTC. The spacecraft was deorbited a few hours later, splashing down in the Pacific Ocean at 15:37 UTC carrying 1,850 kg (4,078 lb) of equipment and science experiments.
SLC-40 - I’m Back
This is the first launch from Space Launch Complex 40 since the Amos-6 accident. During a static fire test of the Falcon 9 rocket September 1, 2016, a structural failure in a second stage COPV caused a carbon fiber to snap and explode, thus destroying the rocket and the payload Spacecom Amos-6 in a massive fire on the pad Space Launch Complex 40.
When the conflagration of the AMOS-6 stack occurred just ahead of the mission’s planned static fire, the brunt of the destruction severely damaged SLC-40’s systems and hardware, including its TEL (Transporter/Erector/Launcher), launch mount, cross-country propellant feed lines, and a significant portion of the pad’s electrical and data lines.
Thankfully, the Horizontal Integration Facility (HIF) and the lightning protection towers were largely spared. Nevertheless, assessments of the pad revealed a significant effort and timeline to rebuild and repair SLC-40, work that did not begin in earnest until February 2017 – over five months after the accident. The reason for the delay was linked directly to the activation of neighboring LC-39A on the Kennedy Space Center.
The five months that followed the AMOS-6 conflagration and the full-up commencement of the reconstruction effort at pad 40, numerous operations took place to assess damage to the pad, clear as much debris as possible, and begin building/ordering equipment needed for the rebuilding effort.
SpaceX was also able to incorporate numerous design changes and equipment upgrades to pad 40, such as new and improved hold down clamps, a brand-new single rocket launch TEL with the same throwback ability debuted on the TEL at LC-39A, as well as brand new GSE Ground Support Equipment, plumbing and electrical and data lines.
The rapid throwback maneuver during launch at T0 clears the TEL from the exhaust plume of a launching Falcon 9, protecting connection points, seals, and propellant lines that can then be reused instead of being scorched and replaced after each mission – as was the case for some elements of the previous TEL at SLC-40.
Moreover, the fact that SpaceX essentially rebuilt SLC-40 in just 10 months (February – November 2017) speaks volumes to SpaceX’s ability to recover from unforeseen events as well as the robustness of the initial pad build and design, with some elements of SLC-40 weathering the AMOS-6 conflagration quite well.
Based on the activation and static fire verification and validation efforts on SLC-40 and combined with 39A, SpaceX will work out the quirks of its newly reactivated pad ahead of the actual CRS-13 launch. As such, teething issues can be expected ahead of the launch.
The static fire took place at 15:00 hours EST for 7 seconds. SLC-40 is now operational.
Now that’s a good question
At 1:18:45 Danny asks Tim about the different layers of atmosphere? Stratosphere and such in detail. Now let’s look at air, rockets and their relations.
Okay here goes nothing. Air is a heavy powerful thing that a rocket must pass through as fast as possible. The ground air pressure is equivalent to 10 meter water depth, so the rocket must push a lot of air a side with its pointy end up, and kick against it with its flammey end down. Newton's second law in action.
At sea level air pressure is 101325 pascals N/m2 or 14,6959 psi. The mass of the atmosphere has a density at sea level of about 1,2 kg per m3, and its density is cut in half exponentially every 5,6 km, so it eventually becomes negligible at 120 km altitude, and there will be thousands of meters between individual air molecules.
During a launch the rocket will reach supersonic speed in just over a minute and reach Max. Q 5 to 15 seconds later, a point or an altitude where air pressure, frozen water vapors and sound vibrations in the rocket can be destructive. The flames from the engines get sucked inside the engine bay and up along the rocket sides, where it could theoretically find a weak spot, exploit it and blow the rocket apart.
That depressurisation caused by the rocket punching a hole through the air can rip the rocket apart, if there is a flaw in the rocket design. Therefore rockets throttle down going through the sound barrier and during the passage of Max. Q. No need to tempt faith or push the envelope during launch.
During ascent the rocket's exhaust gasses increases its size because the atmosphere gets thinner and thinner. The Merlin engine bell are built for sea level air pressure, and they increase in thrust with the decrease of air pressure, but that is not efficient so the engine throttles down to maintain a constant chamber pressure in the engine and to lower the G force on the payload.
The Vacuum Merlin engine has a much bigger engine bell, in which the exhaust gasses can push against each other and the sides of the engine bell giving it an extra push before escaping out into open space, where there is no pressure left to push back.
The Atmosphere above us
The troposphere is the lowest layer of Earth's atmosphere. It extends from Earth's surface to an average height of about 12 km (7.5 mi; 39,000 ft), although this altitude varies from about 9 km (5.6 mi; 30,000 ft) at the geographic poles to 17 km (11 mi; 56,000 ft) at the Equator, with some variation due to weather. The troposphere is bounded above by the tropopause, a boundary marked in most places by a temperature inversion (i.e. a layer of relatively warm air above a colder one), and in others by a zone which is isothermal with height.
Nearly all atmospheric water vapor or moisture is found in the troposphere, so it is the layer where most of Earth's weather takes place. It has basically all the weather associated cloud types generated by active wind circulation, although very tall cumulonimbus thunder clouds can penetrate the tropopause from below and rise into the lower part of the stratosphere. Most conventional aviation activity takes place in the troposphere, and it is the only layer that can be accessed by propeller-driven aircraft.
The stratosphere is the second-lowest layer of Earth's atmosphere. It lies above the troposphere and is separated from it by the tropopause. This layer extends from the top of the troposphere at roughly 12 km (7.5 mi; 39,000 ft) above Earth's surface to the stratopause at an altitude of about 50 to 55 km (31 to 34 mi; 164,000 to 180,000 ft). The atmospheric pressure at the top of the stratosphere is roughly 1/1000 the pressure at sea level. It contains the ozone layer, which is the part of Earth's atmosphere that contains relatively high concentrations of that gas.
The mesosphere is the third highest layer of Earth's atmosphere, occupying the region above the stratosphere and below the thermosphere. It extends from the stratopause at an altitude of about 50 km (31 mi; 160,000 ft) to the mesopause at 80–85 km (50–53 mi; 260,000–280,000 ft) above sea level. Temperatures drop with increasing altitude to the mesopause that marks the top of this middle layer of the atmosphere. It is the coldest place on Earth and has an average temperature around −85 °C (−120 °F; 190 K).
Just below the mesopause, the air is so cold that even the very scarce water vapor at this altitude can be sublimated into polar-mesospheric noctilucent clouds. These are the highest clouds in the atmosphere and may be visible to the naked eye if sunlight reflects off them about an hour or two after sunset or similarly before sunrise.
They are most readily visible when the Sun is around 4 to 16 degrees below the horizon. Lightning-induced discharges known as transient luminous events (TLEs) occasionally form in the mesosphere above tropospheric thunderclouds.
The mesosphere is also the layer where most meteors burn up upon atmospheric entrance. It is too high above Earth to be accessible to jet-powered aircraft and balloons, and too low to permit orbital spacecraft. The mesosphere is mainly accessed by sounding rockets and rocket-powered aircraft.
The thermosphere is the second-highest layer of Earth's atmosphere. It extends from the mesopause (which separates it from the mesosphere) at an altitude of about 80 km (50 mi; 260,000 ft) up to the thermopause at an altitude range of 500–1000 km (310–620 mi; 1,600,000–3,300,000 ft).
The height of the thermopause varies considerably due to changes in solar activity. Because the thermopause lies at the lower boundary of the exosphere, it is also referred to as the exobase. The lower part of the thermosphere, from 80 to 550 kilometers (50 to 342 mi) above Earth's surface, contains the ionosphere. The International Space Station orbits in this layer, between. 350 and 420 km (220 and 260 mi).
The exosphere is the outermost layer of Earth's atmosphere (i.e. the upper limit of the atmosphere). It extends from the exobase, which is located at the top of the thermosphere at an altitude of about 700 km above sea level, to about 10,000 km (6,200 mi; 33,000,000 ft) where it merges into the solar wind. The exosphere contains many of the satellites orbiting Earth.
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