Falcon 9 boost as Merlin 1D engine achieves major milestone

by Chris Bergin

SpaceX’s Merlin 1D engine has achieved flight qualification status during its test program at the company’s rocket development facility in McGregor, Texas. An enhanced design to the engines that have flown on the first five Falcon 9 launches, the Merlin 1D will debut on the first Falcon 9 v1.1 launch this summer.

Merlin 1D:

SpaceX’s Falcon 9 currently employs nine “SpaceX designed and built” Merlin 1C main engines on the First Stage of the rocket.

Merlin 1Cs on the Falcon 9The engines use a propellent fed dual impeller turbo-pump, operating on a gas generator cycle which also provides the high pressure kerosene for the hydraulic actuators, recycling into the low pressure inlet.

The turbo-pump also provides roll control by actuating the turbine exhaust nozzle on the single second stage MVac engine.

Only one engine has suffered from a notable issue during the five successful launches of the Falcon 9, namely Engine 1, which shutdown during the launch of the CRS-1 (SpX-1) Dragon. With a capability to endure the loss of two engines, Falcon 9 still managed to carefully loft Dragon into orbit, ahead of its journey to the International Space Station.

Merlin 1DIt was always in SpaceX’s plans to upgrade the Merlin engine by Flight 6 of their Falcon 9 manifest, with the move to the Merlin 1D providing a vast improvement in performance, reliability and manufacturability, all of which will provide a timely boost to aiding the potential for success for the fully reusable Falcon 9 and their Falcon Heavy.

“Increased reliability: Simplified design by eliminating components and sub-assemblies. Increased fatigue life. Increased chamber and nozzle thermal margins,” SpaceX cited on the improvements for the Merlin 1D, during an interview with NASASpaceflight.com last year.

“Improved Performance: Thrust increased from 95,000 lbf (sea level) to 140,000 lbf (sea level). Added throttle capability for range from 70-100 percent. Currently, it is necessary to shut off two engines during ascent. The Merlin 1D will make it possible to throttle all engines. Structure was removed from the engine to make it lighter.

“Improved Manufacturability: Simplified design to use lower cost manufacturing techniques. Reduced touch labor and parts count. Increased in-house production at SpaceX.”

Merlin 1D testTest firings have been ongoing since at least 2011, with the powerpack achieving a full mission duration firing and multiple restarts at target thrust and specific impulse (Isp). During the 2012 series of testing, the engine fired for 185 seconds with 147,000 pounds of thrust, the full duration and power required for a Falcon 9 rocket launch.

Now, in March, 2013, SpaceX announced the completion of a 28 test qualification program, with the Merlin 1D accumulating 1,970 seconds of total test time, the equivalent run time of over 10 full mission durations.

As such, the milestone allows the company to claim the engine is now fully qualified to fly on the Falcon 9 rocket.

In total, program included four tests at or above the power (147,000 pounds of thrust) and duration (185 seconds) required for a Falcon 9 rocket launch. The Merlin 1D engine was also tested at propellant inlet and operating conditions that were well outside the bounds of expected flight conditions.

“The Merlin 1D successfully performed every test throughout this extremely rigorous qualification program,” said Elon Musk, SpaceX CEO and chief designer. “With flight qualification now complete, we look forward to flying the first Merlin 1D engines on Falcon 9’s Flight 6 this year.”

SpaceX GrasshopperThe Merlin 1D has a vacuum thrust-to-weight ratio exceeding 150, the best of any liquid rocket engine in history. The extra power and multiple restart elements are major steps towards achieving the highly complex task of making Falcon 9 reusable, a vehicle known as F9r, which is currently being tested via the Grasshopper program.

Notably, from a reliability standpoint, SpaceX’s test program demonstrated a ratio of 4:1 for critical engine life parameters such as firing duration and restart capacity to the engine’s expected flight requirements. This is a much higher ratio that the industry standard of 2:1.

The new engine is designed for improved manufacturability by using higher efficiency processes, increased robotic construction and reduced parts count.

The Switch to the V1.1 - Artistic Impression by NSF memberThis will be key for several of SpaceX’s future ambitions, not least their upcoming increase in launch frequency, with the next Falcon 9 – the debut of the V1.1 – set to take place in June, carrying Canada’s space weather satellite, CASSIOPE, out of Vandenberg Air Force Base. (*Falcon 9 V1.1 image left is Photoshopped as to what the F9 V1.1 config may look like*)

Focus will then switch to Cape Canaveral, with two satellite missions, the first carrying SES-8, to be followed by the Thaicom 6 launch, scheduled for the summer.

Back on the West Coast, SpaceX are also preparing to debut their Falcon Heavy launch vehicle. This vehicle will feature 27 Merlin 1D engines on its core and dual boosters, with another Merlin 1D – modified for vacuum operation – providing the role as the second stage engine.

The increase in production has resulted in a busy factory floor at the SpaceX factory in Hawthorne, California, with at least three of the upcoming Falcon 9 v1.1 launch vehicles in an advanced state of production.

(Images: via SpaceX)

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