Waiver of Launch Collective Risk Limit for a Near-Orbital Trajectory

SUPPLEMENTARY INFORMATION:

Background

On April 18, 2024, SpaceX submitted a waiver petition to the Federal Aviation Administration's (FAA's) Office of Commercial Space Transportation (AST) requesting relief from 14 CFR 450.101(a)(1)(i) for a unique near-orbital trajectory SpaceX designed for the initial Starship Super Heavy launches from Boca Chica in Texas. SpaceX requested an increase to the collective risk criteria, to not exceed 2 × 10⁻⁴ E_c, with neither suborbital launch nor suborbital reentry risks exceeding 1 × 10⁻⁴ E_c. SpaceX requested that the waiver be effective for Starship Super Heavy launches starting with Flight 4 and beyond that utilize a near-orbital trajectory, where the maximum perigee altitude is less than +130 km and greater than −50 km. Additionally, SpaceX requested a waiver of the 60-day requirement for submission of waiver petitions per § 404.5(a). SpaceX updated its request on May 17, 2024. with additional rationale to support the waiver petition. On June 4, 2024, the FAA notified SpaceX that the waiver request was still under evaluation and there would be no determination prior to the planned launch of Flight 4 on June 6, 2024. SpaceX requested the FAA consider the waiver for the next flight, namely Flight 5. The request to waive the procedural requirements set forth in § 404.5(a) is no longer applicable as SpaceX since requested the waiver to apply starting with Flight 5.

Near-Orbital Trajectory of Starship Super Heavy Missions

SpaceX's initial developmental test missions are for launches conducted on a near-orbital trajectory, where the nominal trajectory does not achieve orbital insertion as defined in § 401.7.¹ Therefore, the FAA has considered each mission a suborbital launch that includes a suborbital reentry, and has applied a single launch collective risk limit of 1 × 10⁻⁴ E_c in accordance with § 450.101(a)(1)(i). Per § 450.3(b)(3)(iii), for a suborbital launch that includes a suborbital reentry, launch ends after reaching apogee.

The E_c criteria identified in § 450.101 apply to flight. SpaceX, in its waiver petition, divides the phases of Starship Super Heavy flight into two distinct phases. First, SpaceX identifies the launch phase ² to be from ignition of the Super Heavy booster (first stage) to the initial second engine cutoff (SECO-1) of the Starship upper stage. In addition, the launch phase includes stage separation, followed by the Super Heavy booster performing a boostback burn to return to the launch site or a designated landing area offshore. After stage separation, Starship ignites its engines until SECO-1. Due to the shallow perigee of the Starship trajectory after SECO-1, Earth's gravity will cause the Starship to passively enter the Earth's atmosphere in either a controlled or uncontrolled suborbital reentry. For a controlled suborbital reentry, Starship may perform a landing burn prior to ocean splashdown. An uncontrolled suborbital reentry of Starship would almost certainly result in an in-air breakup with debris expected to land within published hazard areas.³ In both scenarios, Starship hazardous debris ⁴ would impact the open ocean between Madagascar and Australia. SpaceX identifies the suborbital reentry phase of the Starship flight to be from SECO-1 of the Starship to its final impact or landing because the perigee only decreases in the post-SECO-1 phases of flight.

Waiver Criteria

Chapter 509 allows the FAA to waive a license requirement if the waiver (1) will not jeopardize public health and safety, safety of property; (2) will not jeopardize national security and foreign policy interests of the United States; and (3) will be in the public interest. See 51 U.S.C. 50905(b)(3); 14 CFR 404.5(b).

Section 450.101(a)(1)(i) Waiver Petition

Section 450.101(a)(1)(i) requires that the risk to all members of the public, excluding persons in aircraft and neighboring operations personnel, must not exceed 1 × 10⁻⁴ E_c . For a suborbital launch, or a suborbital launch with a suborbital reentry,⁵ the 1 × 10⁻⁴ E_c in § 450.101(a)(1)(i) applies from liftoff through final impact or landing. SpaceX's waiver petition is for its Starship Super Heavy missions from Boca Chica that involve a near-orbital trajectory, where the Starship almost obtains the necessary position and velocity to achieve orbital insertion ( i.e., make it into orbit). Because Starship does not achieve orbital insertion, the FAA considers the near-orbital Starship Super Heavy missions to be suborbital in which a single launch collective risk limit of 1 × 10⁻⁴ E_c is applied to cover the sum or aggregate of the risks from the suborbital launch and suborbital reentry phases of each mission. SpaceX seeks relief from the application of a single launch collective risk limit required by § 450.101(a)(1)(i) and requests that the FAA allow for two separate 1 × 10⁻⁴ E_c risk limits, one for the suborbital launch phase and one for the suborbital reentry phase, similar to what is allocated to an orbital mission when a vehicle achieves orbital insertion and then reenters from Earth orbit.

In making a waiver determination, the FAA must analyze whether the waiver: (1) would jeopardize public health and safety or safety of property; (2) would jeopardize national security and foreign policy interests of the United States; and (3) is in the public interest. See51 U.S.C. 50905(b)(3); 14 CFR 404.5(b).

i. Public Health and Safety and Safety of Property

The FAA finds that the trajectory proposed by SpaceX is more like an orbital trajectory than a suborbital trajectory. Because suborbital trajectories do not involve separate, licensable reentries, they are afforded one risk budget. By contrast, orbital trajectories with a return result in a separate and licensable reentry which necessitates a risk budget for launch and a risk budget for reentry. For future flights of the Starship Super Heavy that use this trajectory and end in the Indian Ocean, SpaceX has identified a trajectory that would allow the FAA to apply two separate risk budgets without jeopardizing public health and safety. This increase in the collective risk threshold from 1 × 10⁻⁴ to 2 × 10⁻⁴ E_c, with neither launch nor reentry exceeding 1 × 10⁻⁴ E_c, exposes the public to overall less risk than that of an orbital mission followed by a separate reentry, given the current Starship flight history. SpaceX demonstrated that utilizing the near-orbital trajectory targeting an Indian Ocean landing, which avoids random reentry risk from failures that may occur while on-orbit and provides near certainty that any hazardous debris would impact locations in the Indian Ocean, will not jeopardize public health and safety. The FAA independently found that the public risk associated with a random reentry of the Starship, at this stage in its development, would be 40 to 50 times higher than the collective risk threshold of 1 × 10⁻⁴ E_c. Forcing Starship engine cut-off to occur just prior to reaching orbital perigee (and thus maintaining a suborbital trajectory) allows SpaceX to predict with high certainty debris impact locations given a failure.

For an orbital launch, the criteria in § 450.101(a) apply from liftoff through orbital insertion. For a suborbital launch, or a suborbital launch and reentry, the criteria in § 450.101(a) apply from liftoff through final impact or landing. To determine whether a launch is orbital or suborbital, the FAA determines whether the trajectory is a suborbital trajectory or achieves orbital insertion. The near-orbital trajectory targeting an Indian Ocean landing as proposed by SpaceX does not fully meet the definition of suborbital trajectory per § 401.7, nor does the operation achieve orbital insertion. Specifically, the near orbital trajectory does not fully meet the definition of suborbital trajectory because under § 401.7, a suborbital trajectory is when the vacuum instantaneous impact point (IIP) of a vehicle's flight path does not leave the surface of the Earth. Starship's nominal IIP leaves the earth for a few seconds. Secondly, the near orbital trajectory is not an orbital trajectory because it does not lead to orbital insertion. Orbital insertion is defined in § 401.7 as the point at which a vehicle achieves a minimum 70-nautical mile perigee based on a computation that accounts for drag. In this case, the Starship Super Heavy does not achieve a 70-nautical mile perigee. Because Starship does not achieve orbital insertion, it conducts a suborbital reentry, which is different from a reentry from Earth orbit that involves a final health check prior to initiating deorbit. The near-orbital trajectory presents a unique circumstance as it relates to the application of the safety criteria outlined in § 450.101.

The FAA finds that granting SpaceX a waiver to § 450.101(a)(1)(i) with the following terms and conditions would not jeopardize public health and safety or safety of property:

• The risk to all members of the public, excluding persons in aircraft and neighboring operations personnel, must not exceed 1 × 10⁻⁴ E_c for the phases of flight from the lift-off of the Super Heavy first stage to the initial SECO-1 of Starship.
• The risk to all members of the public, excluding persons in aircraft and neighboring operations personnel, must not exceed 1 × 10⁻⁴ E_c for the phases of flight from the initial SECO-1 to final impact or landing.
• The risk to all members of the public, excluding persons in aircraft and neighboring operations personnel, must not exceed 2 × 10⁻⁴ E_c for all phases of flight from lift-off through final impact or landing.
• The Starship mission profile utilizes a near-orbital trajectory where maximum perigee is less than positive 130 km and greater than negative 50 km, and the normal trajectory limits predicted debris impacts to broad ocean areas in the Indian Ocean.

ii. National Security and Foreign Policy Implications

The FAA has identified no national security or foreign policy implications associated with granting this waiver.

iii. Public Interest

On June 20, 2024, the FAA received a letter from the National Aeronautics and Space Administration (NASA) Human Landing System (HLS) program conveying the importance and criticality of the Starship Super Heavy system and rapid iterations of flight test operations to NASA and its Artemis program. The Starship program, and these test flights, are essential to further the technology required to support the NASA Artemis program and key to returning U.S. Government astronauts to the moon, as reinforced by the letter from NASA. For these reasons, the FAA finds that granting this waiver will be in the public interest.

Endnotes

¹ § 401.7 states that “Orbital insertion means the point at which a vehicle achieves a minimum 70-nautical mile perigee based on a computation that accounts for drag.” Seventy nautical miles equals 130 km.

² The FAA notes that this is different from the FAA's definition of launch in 14 CFR 401.7, which encompasses certain pre- and post-flight activities when the launch occurs from a U.S. site.

³ This is because the loads on the Starship would exceed its structural limits.

⁴ § 401.7 states that “ Hazardous debris means any object or substance capable of causing a casualty or loss of functionality to a critical asset. Hazardous debris includes inert debris and explosive debris such as an intact vehicle, vehicle fragments, any detached vehicle component whether intact or in fragments, payload, and any planned jettison bodies.”

⁵ The FAA introduced suborbital reentry in its experimental permit final rulemaking in 2007 and reaffirmed its position in the Streamlined Launch and Reentry License Requirements final rule (85 FR 79566, 79583 (2020)). The CSLAA describes suborbital rockets as reentering. See 51 U.S.C. 50905(b)(4) and 50906. Congress made clear that a suborbital rocket can “reenter” for purposes of licensing or permitting. It is not necessary to reach orbit to be in outer space. Although a suborbital rocket does not reach the velocity necessary to orbit the Earth, the vehicle can reach altitudes sufficient to be considered outer space.

[FR Doc. 2024-25851 Filed 11-6-24; 8:45 am]

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