Aviation Week & Space Technology - January 15, 2015

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set for Jan. 29. Greaves will be required
to certify this mission prior to launch.
Higher-risk NASA payloads are also
taking longer to certify than anticipat-
ed, with the scheduled March launch
of NOAA’s Jason-3 ocean altimetry
satellite likely delayed as late as June.
NASA is managing Jason-3 construc-
tion and launch for NOAA. SpaceX won
the $82 million contract in July 2012 for
a December 2014 launch, although bud-
get shortfalls prompted a delay.
Since the award, SpaceX has been
working to achieve NASA’s medium-
risk “Category 2” launch certification,
which is required for the Jason-3 mis-
sion. The Falcon 9 was given the nod for
low-risk NASA missions 2.5 years ago.
“The majority of the items [have]
been successfully completed,” NASA
spokeswoman Stephanie Schierholz
said in response to emailed questions.
“However, there are a few open items
SpaceX is working on to fully complete
their certification efort.”
Meanwhile, the company is assess-
ing results of its missed Falcon 9 core-
stage recovery attempt. The first stage
did navigate to the floating barge plat-
form as required, but missed its mark
and was destroyed in the attempt.
Despite the failure, Musk says perfor-
mance of the guidance, navigation and
control (GNC) systems “bodes well” for
a successful recovery in coming tests,
possibly as early as the Dscovr flight.
Following separation, the first stage
was reoriented exo-atmospherically
using nitrogen gas thrusters to en-
able a boost back burn by three of the
vehicle’s nine Merlin 1D engines. The
reentry burn slowed the stage to hy-
personic speed and, with velocity still
above Mach 3, the “X-wing” grid fins
deployed to enable precision targeting.
The fins are designed to control the
stage’s lift vector and move indepen-
dently to control roll, pitch and yaw.
However, because the fins are de-
signed to operate for about 4 min. from
reentry to just before touchdown, they
are actuated by a short-acting open hy-
draulic system. Hydraulic systems are
normally closed, but SpaceX wanted to
reduce complexity and mass, so the sys-
tem loses fluid as it operates. “The grid
fins worked extremely well from hyper-
sonic velocity to subsonic, but ran out of
hydraulic fluid right before landing,” said
Musk in a tweet. “We were about 10%
off. Upcoming flight already has 50%
more hydraulic fluid, so should have
plenty of margin for landing attempt.”

Musk says SpaceX has “no choice”

but to use the aerodynamic fin solution

in place of gaseous nitrogen control

thrusters that were tested to control

a rotation issue that occurred on the

first test flight in September 2013. “En-

try velocity is too high for a precision

landing with nitrogen thrusters alone.

We must have aerodynamic surfaces

for pitch trim,” he says. Prototype ver-

sions of the steerable fins were first

tested last May on a flight trial of the

Falcon 9 Reusable (F9R) experimental

vehicle that reached an altitude of 1,000

meters (3,280 ft.). SpaceX is developing

a new F9R after the first was destroyed

in August during a trial at its rocket de-

velopment facility in McGregor, Texas.

Although the first-stage control au-

thority was severely depleted by the time

it was close to touchdown, the GNC sys-

tem was able to efect limited directional

control via gimbaling of a single Merlin,

which is used for the final braking de-

scent maneuver. Despite this, the stage

“landed hard,” according to SpaceX,

narrowly missing the correct section of

the 300 X 100-ft. landing platform and

damaging support structures around

the edge of the converted barge. c

Amy Butler Washington

Engagement Window

Lockheed dusts of Thaad-ER design as counter

to Chinese hypersonic boost glide vehicle

L

ockheed Martin is hoping the

maturing threat of hypersonic

boost glide vehicles from ambi-

tious adversaries will spark interest

in the company’s dormant plan to de-

sign a more capable interceptor for the

Terminal High-Altitude Area Defense

(Thaad) air defense system.

Chinese ofcials confirmed they con-

ducted a test last month of what they

are calling a hypersonic strike vehicle.

U.S. ofcials worry this missile could

outsmart their defenses.

The U.S. has spent considerably

more than $100 billion to perfect hit-

to-kill technology and improve connec-

tivity among disparate systems fielded

for protection against air-breathing

and ballistic missile threats. The Army

plans to field at least six Thaad batter-

ies; the system is designed to field an

area defense system capable of inter-

cepts both inside the atmosphere and

in the low regions of space.

Today, the U.S. has no optimal ca-

pability to intercept an advanced hy-

personic boost glide vehicle, according

to an industry source. Although hyper-

sonic vehicles burn hot and are thus

easily visible to the U.S. sensor net-

work, they are maneuverable. There

is concern that existing interceptors

in the U.S. arsenal lack the divert ca-

pabilities required to counter such a

threat.

However, a credible threat does not

yet exist. The vehicles tested by the

Chinese are considered to be basic,

but Missile Defense Agency (MDA)

Director Vice Adm. James Syring is

said to be more concerned about Rus-

sia’s hypersonic systems, which are far

more maneuverable and advanced. He

has already advocated quietly in the

Pentagon for funding for a Thaad-ER

to address what he sees as a gap in in-

tercept capability should these threats

get fielded. So far, his eforts have not

paid of.

Development of ofensive hyperson-

ic systems is “one of the key reasons”

a Thaad-ER (extended range) missile

should be considered for introduction

into the Pentagon arsenal, says Mike

Trotsky, vice president of air and

missile defense for Lockheed Martin,

which produces Thaad.

“We see a growing interest in this

capability. We are working to define

what, specifically, this system would

look like... to give it the divert capa-

bility necessary to address some of the

emerging threats we are seeing,” said

Doug Graham, vice president of ad-

vanced programs for Lockheed Martin

Strategic & Missile Defense Systems.

“One of the things the MDA is look-

ing very closely at is the upgrade of

the Thaad system to the ER configu-

ration so we can extend the reach of

DEFENSE