Six months after its 19th mission ended in pieces falling from the sky, SpaceX’s new and improved Falcon-9 booster is set for a long-awaited Return to Flight (RTF), no sooner than Sunday night, Dec. 20, carrying with it 11 Orbcomm Generation-2 (OG-2) communications satellites for delivery into low-Earth orbit. While the launch itself is the mission, delivering their customer’s payload, the flight also gives SpaceX another opportunity for a secondary objective: to land their rocket’s first stage booster, something the company has been working toward in an effort to provide a rapidly reusable and cheaper launch system.
Sunday’s RTF will mark the first time a rocket landing has ever been attempted at the nation’s historic Cape Canaveral launch site, and liftoff is currently scheduled for a 60-second window at 8:29 p.m. EST.
SpaceX has attempted to land a first stage Falcon-9 on the company’s Autonomous Spaceport Drone Ship (ASDS) offshore twice previously. Each time SpaceX hit the mark, but both times the booster tipped over. An attempt to land during the CRS-5 launch in January achieved partial success, reaching the deck, but impacted hard at a 45-degree angle and exploded, primarily due to a premature exhaustion of hydraulic fluid in its hypersonic grid fins. A second attempt was planned for the DSCOVR launch in February, but was called off due to rough sea conditions, and the most recent attempt during April’s CRS-6 launch reached the deck, but touched down with excessive lateral velocity and toppled over upon impact.
Comments from NASA and the Air Force earlier this month confirmed that SpaceX was pressing ahead with plans to land the Falcon-9 RTF Orbcomm first-stage booster on solid ground, rather than aboard the deck of the ASDS in the Atlantic Ocean. Media visiting SpaceX pad 39A at Kennedy Space Center on Dec. 1 were greeted by NASA Commercial Crew Program representatives, who hinted to the possibility in the first place.
The 45th Space Wing at Patrick Air Force Base, responsible for all launches from Florida’s “Space Coast,” offered more clarification shortly after, noting that “SpaceX is waiting on Federal Aviation Administration (FAA) approval for both return to flight and doing a land landing vs. drone ship” in response to media inquiry.
Earlier this year, the 45th Space Wing signed a five-year lease with SpaceX to create a “Landing Pad” at Cape Canaveral Air Force Station’s historic Launch Complex-13. Utilized for Atlas Intercontinental Ballistic Missile (ICBM) tests and operational Atlas launches from August 1958 through April 1978, LC-13 was deactivated in 1980. More than three decades passed before SpaceX leased it last February, and efforts to construct five landing pads for its returning Falcon-9 first-stage hardware soon got underway.
The site is now designated “Landing Zone-1.”
This morning, SpaceX CEO Elon Musk took to Twitter to confirm the company is still targeting a Sunday night launch attempt, as well as a landing attempt of their booster on Cape Canaveral, rather than on their ASDS barge, which set sail from Jacksonville earlier this week.
“Currently looking good for a Sunday night (~8pm local) attempted orbital launch and rocket landing at Cape Canaveral,” said Musk.
The company released additional details later in the day, advising communities on Florida’s Space Coast of the possibility of a sonic boom occurring as the booster plummets back to Earth. The last time sonic booms cracked across the Cape’s landscape for a returning vehicle from space was the Space Shuttle Atlantis in July 2011.
“Residents of the communities of Cape Canaveral, Cocoa Beach, Courtenay, Merritt Island, Mims, Port Canaveral, Port St. John, Rockledge, Scottsmoor, Sharpes, and Titusville in Brevard County, Fla. are most likely to hear a sonic boom, although what residents experience will depend on weather conditions and other factors,” said the press release.
Workers at neighboring Kennedy Space Center also received a security notice Friday advising them of road closures. The advisory also stated, “should there be an anomaly, personnel are to shelter in place and avoid being next to glass windows and doors. Should a shelter in place event occur employees and guests on KSC will be informed by the Paging Area Warning System (PAWS) when to shelter in place and when it is safe to leave. Parking on the shoulder of any road to view launch or landing is unauthorized.”
SpaceX has confirmed that, although the ASDS was offshore this week, it will NOT serve as an alternative landing pad. SpaceX is committed to LZ-1; the booster either falls in the ocean or lands at LZ-1.
Throughout the year SpaceX has been quietly busy at LZ-1, repurposing the former launch complex to successfully support construction of a vertical-landing facility suitable for returning Falcon-9 and Falcon Heavy boosters. A primary concrete landing pad has been developed, surrounded by four smaller contingency landing pads for use in case a descending rocket is not quite on the bull’s-eye.
The FAA concluded an environmental review earlier this month for SpaceX to start landing boosters at LZ-1, known as the “Finding of No Significant Impact” (FONSI), which notes that there would be no major environmental issues related to the company’s plans. Various environmental factors were considered, with the FAA determining all systems GO for SpaceX pending additional FAA approvals needed before an LZ-1 landing attempt was cleared (such as air space during a Christmas holiday week).
The Falcon’s first stage will touch down at LZ-1 approximately 10 minutes after lift-off, and preliminary trajectory analysis from the “Environmental Assessment for SpaceX Vertical Landing of Falcon-9 and Construction at Launch Complex 13” indicates that a point directly beneath the vehicle at stage separation falls approximately 16 nautical miles from the launch site.
Stabilizing the 150-foot-tall rocket stage in flight—traveling at a velocity of 2,900 mph at separation—has been likened to someone balancing a rubber broomstick on their hand in the middle of a fierce wind storm. After first stage engine cutoff, exoatmospheric cold gas thrusters are triggered to flip the first stage into position for retrograde burn. Three of the rocket’s nine Merlin engines are then restarted to conduct the retrograde burn in order to reduce the velocity of the booster and to place it in the correct angle to land. Once the first stage is in position and approaching its landing target, two of the three engines will be shut down to end the boost-back burn.
Utilizing compressed helium to deploy its four extendable landing legs, the booster and a quartet of lattice-like hypersonic grid fins, configured in an “X-wing” layout, will then be unfurled to control the rocket’s lift vector, and a final single engine burn will slow the stage to a velocity of zero for a stable landing at LZ-1.
An approximately 200 foot by 200 foot concrete landing pad was designed to support the weight and thrust energy of the booster landing, and it is surrounded by an approximately 750 foot diameter of compressed soil and gravel. Four additional, 150 foot diameter concrete “contingency” pads serve as backups, and will only be utilized in order to enable the safe landing of a single vehicle should last-second navigation and landing diversion be required.
The draft also notes, “There are no plans to utilize the contingency pads in order to enable landing multiple stages at LC-13 during a single landing event.” However, a SpaceX video animation showing a trio of Falcon Heavy boosters landing at the same time on LZ-1 indicates otherwise, so who knows what the future holds at this time.
Two access roads have been constructed to those contingency pads for use of a retrieval crane following landings, and at the location of the former blockhouse a steel and concrete “stand” had to be built to secure the Falcon stage during post-landing operations. The stand consists of four individual pedestal structures bolted to a concrete base. Each of the four pedestals weighs approximately 15,000 pounds and is 107 inches tall and 96.25 inches wide. A mobile crane will be used to lift the stage from the landing pad, transport it, and place it on the stand. Activities such as allowing the landing legs to be removed or folded back to the stage (flight position) prior to placing the stage in a horizontal position would occur there.
Although propellants are burned to depletion during flight, there is a potential for some LOX and RP-1 to remain in the Falcon first stage upon landing, as well as a small amount of ordnance, such as small explosive bolts and on-board batteries. It is very possible that the booster won’t land perfectly, as it is still a developing vehicle and these landing attempts are tests, so to be safe SpaceX will have an established emergency response team standing by to contain any unexpected spills (if, for example, the booster tips over upon landing and cracks open, as previous boosters toppled over on the ASDS).
Safing activities will begin upon completion of all landing activities and engine shutdown. The LOX oxidizer system will be purged, and any excess fuel will be drained into a suitable truck-mounted container or tanker. Any remaining pressurants (i.e., helium or nitrogen) will be vented, and any FTS explosives will also be rendered “inert” prior to declaring the vehicle safe. The vehicle will then be lifted and placed on to the stand, followed by the landing legs being removed or folded back into place. Falcon-9 will then be lowered into a horizontal position, placed on a transport vehicle, and taken to a SpaceX facility.
Assuming the booster lands in one piece, it is expected that SpaceX will use it as a test article to practice and prepare KSC’s historic Launch Complex 39A for upcoming operational missions with the Falcon-9, Falcon Heavy, and crewed flights to the International Space Station (ISS). SpaceX signed a 20-year lease for the former Apollo and space shuttle launch site in spring 2014.
“The first stage, if they successfully get it back, will then be the test article here (39A), and it will go into the hangar where they (SpaceX) will do a little refurbishment, and they will actually put it on the transporter erector and roll it out to the pad to do fluid checks, electrical checks and propellant loading with that test article,” said NASA.
The current launch weather forecast continues to predict partly cloudy conditions, with a 20-percent probability of rain. However, it has been noted by the 45th Weather Squadron that a 90-percent probability of acceptable conditions is expected for a launch attempt Sunday night.
The rocket stage falling back to Earth, firing its engines in stages to slow its descent, was clearly visible as it aimed for an attempted landing on the ASDS after launching the CRS-4 Dragon mission to resupply the ISS for NASA on Sept. 21, 2014, and that was over 200 miles from the launch site, so a nighttime booster landing attempt at LC-1 will be clearly visible to those watching around Cape Canaveral.
Jetty Park, Port Canaveral Cape Canaveral, and the 528 Beachline Causeway south of Cape Canaveral AFS are the best locations from which the public can watch, as all will provide clear views of launch and landing. Beaches running south from the Cape will also serve as good viewing locations.
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