Document ID: FAA-2010-1225-0001
Agency: faa
Document Type: Rule
Title: Waivers of Autonomous Reentry Restrictions for Reentry Vehicles
Posted Date: 2010-12-06T05:00Z

[Federal Register Volume 75, Number 233 (Monday, December 6, 2010)]
[Rules and Regulations]
[Pages 75621-75624]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2010-30399]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 431

Office of Commercial Space Transportation; Waiver of Autonomous 
Reentry Restriction for a Reentry Vehicle

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of waiver.

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[[Page 75622]]

SUMMARY: This notice of waiver concerns two petitions for waiver 
submitted to the Federal Aviation Administration (FAA) by Space 
Exploration Technologies Corp. (SpaceX): A petition to waive the 
requirement that a waiver petition be submitted at least sixty days 
before the proposed effective date of the waiver, and a petition to 
waive the requirement that SpaceX only initiate reentry of its reentry 
vehicle, the Dragon Spacecraft (Dragon), by command. The first petition 
is unnecessary because, as explained below, SpaceX demonstrated good 
cause for its late filing. The FAA finds that waiving the requirement 
for SpaceX ground operators to initiate Dragon's reentry to Earth is in 
the public interest and will not jeopardize public health and safety, 
safety of property, and national security and foreign policy interests 
of the United States.

FOR FURTHER INFORMATION CONTACT: For technical questions concerning 
this waiver contact Howard Searight, Aerospace Engineer, AST-200, 
Office of Commercial Space Transportation (AST), Federal Aviation 
Administration, 800 Independence Avenue, SW., Washington, DC 20591; 
telephone (202) 267-7927; e-mail: howard.searight@faa.gov. For legal 
questions concerning this waiver contact Laura Montgomery, Senior 
Attorney for Commercial Space Transportation, AGC-200, Office of the 
Chief Counsel, Regulations Division, Federal Aviation Administration, 
800 Independence Avenue, SW., Washington, DC 20591; telephone (202) 
267-3150; e-mail: laura.montgomery@faa.gov.

SUPPLEMENTARY INFORMATION:
    Background: On September 23, 2010, SpaceX requested two waivers 
from the FAA's Office of Commercial Space Transportation (AST) for the 
reentry of Dragon, a reentry vehicle, to be launched on Falcon 9 flight 
002. First, SpaceX requested a waiver of procedural requirements for 
waivers set forth at 14 CFR 404.3. Second, SpaceX requested a waiver of 
14 CFR 431.43(e)\1\ to allow autonomous reentry.\2\
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    \1\ Even though Dragon is a reentry vehicle and not a reusable 
launch vehicle, 14 CFR 435.33 incorporates and applies section 
431.43 to all reentry vehicles.
    \2\ SpaceX stated that autonomous reentry would only be used in 
off-nominal circumstances, and the regulation prevents autonomous 
reentry only for nominal circumstances, thus rendering a waiver 
unnecessary. This interpretation of the regulation conflicts with 
the regulation's requirement that an operator only initiate reentry 
by command as described in the preamble to the proposed rule. There, 
the FAA expressed its concern that authorizing reentry of totally 
autonomous vehicles would not fulfill adequately its public safety 
responsibility. Without active control, those systems and conditions 
necessary for safe reentry would not be verified before reentry was 
initiated Commercial Space Transportation Reusable Launch Vehicle 
and Reentry Licensing Regulations, 64 FR 19626, 19645 (Apr. 21, 
1999) (Reentry NPRM). Because it was the FAA's intent that the 
regulations ensure human control capability upon reentry, SpaceX's 
petition is a request for a waiver.
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    The FAA licenses, in relevant part, the launch of a launch vehicle, 
and reentry of a reentry vehicle under authority granted to the 
Secretary of Transportation by 49 U.S.C. Subtitle IX, chapter 701 
(Chapter 701), and delegated to the FAA's Administrator and Associate 
Administrator for Commercial Space Transportation.
    SpaceX is a private commercial space flight company. It entered 
into a Space Act Agreement with the National Aeronautics and Space 
Administration (NASA) as part of NASA's Commercial Orbital 
Transportation Services (COTS) program. The COTS program is designed to 
stimulate efforts within the private sector to demonstrate safe, 
reliable, and cost-effective space transportation to the International 
Space Station.
    SpaceX's petition for waiver concerns an upcoming demonstration 
flight that it plans to undertake as part of the COTS program. At the 
time of the filing of the petition, the launch for that flight was 
scheduled to take place on November 8, 2010. During the flight, 
SpaceX's Falcon 9 vehicle will launch the Dragon reentry vehicle into 
orbit. Dragon is a reentry vehicle whose capability SpaceX plans to 
demonstrate for NASA. Ultimately, SpaceX intends to use Dragon to 
transport cargo and people to and from the International Space Station.
    Once Dragon is in orbit, a ground-implemented health check will be 
carried out by telemetry. SpaceX has designed the Dragon capsule to 
remain in orbit until SpaceX ground operators transmit a reentry 
command. A ground operator can issue commands to either enable or 
disable the reentry of Dragon based on the health of the vehicle. 
Dragon is also able to conduct an autonomous health check. Propellant 
and power levels are the key variables used by ground operators in 
determining whether to issue commands to reenter or stay in orbit, and 
the same variables would be used by the vehicle in its onboard health 
check. The onboard health check is designed to check time-dependent 
variables to ensure the health and functionality of the propellant, 
power and avionics sub-systems. Based on these evaluations, Dragon is 
able to determine whether it is healthy. On the ground, the reentry 
team can read the raw data and establish for themselves whether Dragon 
is healthy. Dragon's onboard health check is designed to replicate the 
decision-making process of the ground operators with respect to time-
dependent failures, which are, in Dragon's case, the full depletion of 
power and propellant. If Dragon's communications failed and the vehicle 
passed the onboard health check, Dragon would reenter autonomously.
    Once Dragon passes a ground-implemented health check, ground 
operators will issue a reentry command. After ground operators issue 
the reentry command, Dragon will wait until the point in space at which 
the reentry burn initiation is planned before initiating reentry. 
Dragon will reenter, deploy three parachutes and splash down. A nominal 
Dragon reentry splashes down in the Pacific Ocean off the coast of 
southern California with some propellants on board.
    If an anomaly occurs after the issuance of the reentry command, 
ground operators can issue a command that disables reentry. SpaceX is 
concerned with what would happen if its ground operators were unable to 
communicate a reentry command to a healthy Dragon due to failed or 
disabled communications. In this circumstance, SpaceX proposes that the 
FAA permit the autonomous reentry of a healthy Dragon at the nominal 
landing location in order to maximize public safety. This scenario may 
play out in different ways. If ground operators needed more time to 
complete a health check than that available during one orbit, they 
could disable reentry by command. Dragon would then not reenter, even 
if its autonomous health check would otherwise allow it to. If a health 
check proved satisfactory, ground operators could re-enable reentry, 
and Dragon would reenter. If Dragon never received a command, it could 
rely on the results of its own continuous autonomous health check, and, 
if those results were positive, reenter.
    Dragon has several safety features that would allow for a safe 
autonomous reentry in the event of a communications failure, including: 
(1) The vehicle automatically reduces itself to its lowest energy level 
in the case of an off-nominal burn; (2) the vehicle has the ability to 
autonomously guide itself to the same pre-determined landing site, 
located more than 780 kilometers from the coastline; (3) the vehicle 
has the ability to monitor its safety-critical systems in real-time; 
(4) the vehicle has over 100% margin on both power and propellant 
budgets; (5) the vehicle has a space-grade inertial measurement unit 
(IMU); (6) the vehicle

[[Page 75623]]

has a space-grade flight computer; and (7) the vehicle has redundant 
drogue parachutes and dual redundant main parachutes.
    Waiver Criteria: Chapter 701 allows the FAA to waive a requirement 
for an individual license applicant if the FAA decides that the waiver 
will not jeopardize public health and safety, safety of property, and 
national security and foreign policy interests of the United States and 
is in the public interest. 49 U.S.C. 70105(b)(3) (2010); 14 CFR 
404.5(b) (2010).

Section 404.3 Waiver Petition

    Section 404.3(b)(5) requires that a petition for waiver be 
submitted at least sixty days before the proposed effective date of the 
waiver. However, this section also provides that a petition may be 
submitted late if the petitioner shows good cause. Id. (b)(5).
    Here, SpaceX submitted its waiver petition on September 23, 2010, 
which was less than sixty days before the November 8, 2010 launch date 
planned at the time of the filing of the petition. However, in its 
petition, SpaceX explained that it initially interpreted the applicable 
regulations differently than the FAA, and was not aware that a waiver 
would be required. Once the FAA informed SpaceX that it needed to 
obtain a waiver, SpaceX proceeded to apply for the waiver in a timely 
fashion. As such, the FAA has found that SpaceX had good cause for 
submitting its waiver petition less than sixty days from its launch 
date. Therefore, SpaceX's late submission does not violate 404.3(b)(5), 
and a waiver of that section is unnecessary.

Section 431.43(e) Waiver Petition

    Section 431.43(e) requires, in pertinent part, any operator of a 
reusable launch vehicle that enters Earth orbit to issue a command 
enabling reentry flight of the vehicle. It further states that reentry 
flight cannot be initiated autonomously under nominal circumstances 
without prior enable. 14 CFR 431.43(e).
    For reasons described below, the FAA waives the requirement of 14 
CFR 431.43(e), and allows SpaceX to autonomously initiate reentry 
flight of Dragon in the event that SpaceX ground operators lose 
communication with Dragon, and Dragon is healthy. In this context, 
communication loss means Dragon fails to send a reentry request to 
SpaceX's ground operators, or the ground operators are unable to send a 
command enabling reentry of Dragon. The onboard health check is 
designed to check time-dependent variables to ensure the health and 
functionality of the propellant, power and avionics sub-systems.
    In deciding whether or not to waive the requirement that Dragon's 
operator issue a command to enable reentry of the vehicle, the FAA must 
analyze whether the waiver: (1) Is in the public interest; (2) will not 
jeopardize public health and safety or safety of property; and (3) will 
not jeopardize national security and foreign policy interests of the 
United States. 49 U.S.C. 70105(b)(3); 14 CFR 404.5(b). The FAA will 
grant this waiver because SpaceX satisfies the criteria.

A. Public Interest

    The change proposed by SpaceX is consistent with the statutory goal 
of seeking improvements to safety. 49 U.S.C. 70101(a)(12) and 
(b)(2)(C). Granting SpaceX's waiver is in the public interest because a 
guided reentry is safer than a random reentry, and therefore Dragon's 
proposed autonomous reentry capability enhances the overall safety of 
the mission.

B. Public Health and Safety

    Although the FAA's regulation prohibits autonomous reentry, a 
waiver is warranted in SpaceX's case because an autonomous reentry of a 
healthy Dragon that has lost ground communications is safer than a 
random reentry. The preamble to the Reentry NPRM acknowledges that some 
RLV operators were contemplating totally autonomous reentry capability, 
and expressed a concern that autonomous reentry was not adequately 
safe. Specifically, the FAA was concerned about system anomalies or 
other non-compliant conditions that would not be verified before 
initiation of reentry in the absence of active human control. Reentry 
NPRM, 64 FR at 19645. The FAA retained flexibility in granting waivers 
to allow the use of autonomous systems. Commercial Space Transportation 
Reusable Launch Vehicle and Reentry Licensing Regulations, 65 FR 56618, 
56641 (Sept. 19, 2000) (Reentry Rule). In requiring the capability for 
human intervention, the FAA did not intend to foreclose the use of 
autonomous systems or autonomous decision-making. Id. SpaceX's proposed 
approach addresses the concern underlying the regulatory requirements 
and poses less risk than that associated with Dragon being left in 
orbit to reenter randomly at some later time. SpaceX's mitigation 
measures are of additional importance to the FAA's decision to grant a 
waiver.
    The FAA's reason for requiring commanded reentry was to make sure 
that an operator had the chance to verify that there were no system 
anomalies or other non-compliant conditions. Under SpaceX's proposed 
plan, the operator would employ two means of detecting any such 
anomalies. Ground operators and Dragon's own continuous autonomous 
health check would both perform health checks to determine whether 
conditions prohibited reentry.
    To determine the effect of granting SpaceX's waiver on public 
safety, the FAA performed a risk analysis of potential reentry 
outcomes. The risks of leaving the vehicle in orbit or attempting a 
reentry (whether autonomous or commanded) are best compared by applying 
conditional probabilities, where an undesired event is assumed to 
happen, to each possibility. For purposes of comparison, in the two 
cases discussed below, the FAA assumes that Dragon fails to expel its 
propellant, and its parachutes fail to deploy, resulting in an 
explosive impact.
    In a random reentry scenario, Dragon has lost communications and is 
unable to reenter autonomously. The FAA assumed a 100% probability of 
leaving the vehicle in orbit with a full propellant load. The vehicle 
would continue circling the Earth until it reentered randomly due to 
natural orbital decay. The FAA assumed the impact probability in a 
given latitude band was equivalent to the dwell time of the vehicle in 
orbit over that latitude band. The FAA computed the population density 
as a function of latitude by dividing the population within each 
latitude band under Dragon by the Earth's surface area within each 
latitude band. The FAA applied a sheltering model based on surveys and 
socioeconomic factors, including population density and distribution 
and the types of homes people live in, all of which affect expected 
casualties. The conditional risk computed for a random reentry produced 
an expected average number of casualties (Ec) of 
approximately 23 x 10-3.
    In an autonomous reentry scenario, Dragon has lost communications 
and is attempting an autonomous reentry. The FAA assumed a 100% 
probability of reentry burn failure at any time from burn initiation to 
burn cutoff, assuming a uniform failure rate. In this scenario, Dragon 
remains orbital for two-thirds of its burn. Two-thirds of the 
conditional random reentry risk calculated above results in an 
Ec of approximately 15 x 10-3. The remaining risk 
results from an assumed failure during the last third of the reentry 
burn when the vehicle is no longer in orbit. This results in a flight 
corridor extending from the Atlantic to the Pacific crossing over the 
continental

[[Page 75624]]

United States and Northern Mexico. The conditional risk along this 
flight corridor is approximately Ec 13 x 10-3. 
The FAA multiplied 13 x 10-3 by one-third, to account for 
the fact that this failure mode is only applicable to one-third of the 
burn, which results in an Ec of 41 x 10-4. The 
total conditional risk associated with an autonomous reentry, where a 
burn failure is assumed, is 19 x 10-3. Thus, there is 
theoretically 20% less risk in an attempt to reenter Dragon than there 
is in leaving it in orbit given a communications failure.
    Also of importance to the FAA's decision to grant a waiver, Dragon 
is equipped with a number of mitigating features. First, the vehicle 
automatically safes itself in the case of an off-nominal burn. This 
means that if Dragon conducted its reentry burn, but computed that the 
desired landing spot would not be achieved, it would vent the rest of 
its fuel, thereby reducing the possibility of explosion or dispersion 
of toxic fumes on impact. Second, the vehicle has the ability to 
autonomously guide itself to its planned landing location in the 
Pacific Ocean, some 780 kilometers from the coastline. This internal 
capability allows Dragon to act independently, based on programmed 
instructions and information regarding its location, if communications 
with the ground are lost. Third, the vehicle has the ability to monitor 
its safety-critical systems in real-time. This means Dragon has near-
immediate awareness of the operability of its on-board systems that 
allow it to operate safely, and this awareness enables Dragon to react 
in time to conduct a reentry. Fourth, the vehicle has a space-grade IMU 
and flight computer. This means Dragon is equipped with a system that 
provides information on where Dragon is, which is pertinent to its 
guidance capabilities, and the IMU and flight computer are designed and 
tested to operate in the rigorous conditions of space.

C. National Security and Foreign Policy Implications

    The FAA has not identified any national security or foreign policy 
implications associated with granting this waiver.
    Summary and Conclusion: A waiver is in the public interest because 
it accomplishes the goals of Chapter 701 and decreases risk to the 
public. The waiver will not jeopardize public health and safety or 
safety of property because allowing autonomous reentry of a healthy 
Dragon vehicle that has lost all communications presents less risk than 
a random reentry. A waiver will not jeopardize national security and 
foreign policy interests of the United States. For the foregoing 
reasons, the FAA has waived the requirement of 14 CFR 431.43(e) for a 
commanded reentry, and allows SpaceX to autonomously initiate reentry 
flight of Dragon in the event that all communication between ground 
operators and Dragon has been lost, and Dragon is healthy.

    Issued in Washington, DC on November 30, 2010.
Kenneth Wong,
Licensing and Safety Division Manager.
[FR Doc. 2010-30399 Filed 12-3-10; 8:45 am]
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