Blue Origin has conducted the fifth flight of the same reusable straight up/straight down suborbital rocket booster on Wednesday in a test that allows the company to validate in-flight performance of its new pusher abort system for the New Shepard capsule. The flight involved a pre-planned abort scheduled for 45 seconds into flight at an altitude of 16,000 feet and unexpectedly saw the booster safely return.
In-flight abort test:
In what was the company’s fourth successful test flight this year, Blue Origin conducted a crucial in-flight abort test of its new pusher abort system that’s designed to safely separate the New Shepherd crew capsule from the New Shepard booster in the event of an anomaly during powered flight.
The test was a crucial step for Blue Origin in its desire to eventually ferry paying customers on suborbital flights.
While the company has already proven that the New Shepard crew capsule’s parachutes can operate under normal and anomalous conditions, they had not yet tested the new pusher abort system in flight.
As stated by Blue Origin CEO, Jeff Bezos, “Like Mercury, Apollo, and Soyuz, New Shepard has an escape system that can quickly propel the crew capsule to safety if a problem is detected with the booster.
“Our escape system, however, is configured differently from those earlier designs.”
The primary difference for New Shepard is that unlike NASA’s designs where the abort system is attached to a tower that pulls the capsule clear of a malfunctioning booster stage, Blue Origin’s abort system – like SpaceX – relies on a system of thrusters attached to the crew capsule itself.
This kind of pusher abort system allows the thrusters, like the capsule, to be reused or re-flown – unlike NASA’s approach which sees the escape tower jettison and lost after each mission.
Mr. Bezos expanded on this, stating that “Expending an escape motor on every flight drives up costs significantly. Further, the jettison operation is itself safety critical. Failure to jettison the tower is catastrophic.”
While a normal mission of New Shepherd will not see the escape motor used, it has nonetheless undergone extensive ground testing, as well as a pad abort test.
Now, it was tested in flight.
“This upcoming flight will be our toughest test yet,” noted Mr. Bezos. “We’ll intentionally trigger an escape in flight and at the most stressing condition: maximum dynamic pressure through transonic velocities.”
Following liftoff – and after a number of holds – the New Shepard booster ascended with its capsule to an altitude of 16,000 ft – at which point an anomalous condition was simulated and a command to initiate the abort sequence was issued.
At this point, a series of redundant separation systems aboard the capsule severed the crew module from the booster at the same moment the escape motor itself ignited – thrusting the module with 70,000 lbf through a brief, 2-second high acceleration event away from the booster.
The abort occurred right as the booster reaches the area of maximum aerodynamic pressure, or MaxQ – which is the most-difficult command and control and stressful period of flight in which an abort can occur.
Once the abort motor fired and began pushing the capsule away from the booster, the engine underwent a series of gimbals – thrusting the capsule away from the flight path of the booster in a quickly diverging flight profile.
Once safely away from the booster, the capsule continued coasting in a somewhat parabolic arc before reaching the apex of its trajectory – at which point its three parachutes deployed and it will began to descend back to the ground.
Moreover, unlike previous tests which were designed to safely recover the New Shepherd booster itself and demonstrate safe and reliable reusability of the suborbital rocket, this test carried no such objective.
While it was classed as possible for the booster to survive the in-flight abort, it was noted that the booster itself was not designed to survive such an event, especially given the off-axis 70,000 lbf that will be delivered to the top of the booster via the escape motor.
According to Mr. Bezos, “The booster was never designed to survive an in-flight escape. The capsule escape motor will slam the booster with 70,000 pounds of off-axis force delivered by searing hot exhaust.
“The aerodynamic shape of the vehicle quickly changes from leading with the capsule to leading with the ring fin, and this all happens at maximum dynamic pressure. Nevertheless, the booster is very robust and our Monte Carlo simulations show there’s some chance we can fly through these disturbances and recover the booster.
“In the more likely event that we end up sacrificing the booster in service of this test, it will still have most of its propellant on board at the time escape is triggered, and its impact with the desert floor will be most impressive.”
Regardless, safe recovery of the booster was not a test priority for this flight – as a successful test of the in-flight abort system will pave the way for Blue Origin to apply through the Federal Aviation Administration for the proper permits to begin ferrying paying passengers on suborbital flights of their New Shepard rocket.
Ironically, the booster did survive the event and returned for its fifth landing. It will now be retired.
In all, the company has enjoyed great success with its New Shepard suborbital, reusable booster that’s designed to serve as a commercial space tourism vehicle for paying customers interested in spending a brief amount of time in microgravity.
Prior to Wednesday’s flight, Blue Origin completed four successful test launches and landings of its straight-up/straight-down suborbital vehicle.
The first New Shepard flight took place in April 2015 and saw the rocket launch successfully, delivering its Crew Capsule to an altitude of 307,000 ft – still inside Earth’s atmosphere and below the Karman line, the internationally recognized point (100 km, 62.13 mi, 328,084 feet in altitude) at which aeronautics ends and astronautics begins.
That first test did not result in the recovery of the booster because of a loss of pressure event in the booster’s hydraulic system.
The second flight occurred in November 2015 and saw the New Shepard booster loft its Crew Module to an altitude of 329,839 feet before returning under powered control to an upright landing – marking the first time a suborbital rocket successfully landed after a straight-up/straight-down flight.
The third full-scale test flight of the entire New Shepard system then occurred in April 2016 in a test to provide in-flight use of a new, more efficient Reaction Control System algorithm on the capsule as well as fly two microgravity experiments inside the capsule.
With those three successful tests of the same booster under its belt, Blue Origin embarked on its fourth test, which again tested the New Shepard’s ability to launch and land successfully.
Importantly, the fourth test provided valuable, in-flight data and risk assessment for a single-parachute out scenario for New Shepard’s capsule.
According to Blue Origin, “On this flight, [we] intentionally [failed] one string of parachutes on the capsule.”
Gliding back to Earth under two chutes instead of three, the capsule made use of its retro thrust system to properly decelerate to a safe human-rated landing velocity.
This was an important step in Blue Origin’s desire to ferry tourists to microgravity as the company’s investors and potential customers need to have confidence that the capsule’s critical landing systems have enough redundancies to safely return passengers to Earth in the event of an off-nominal flight event.
(Images: Blue Origin)