# Why do SpaceX expect the Falcon 9 rocket to explode during the in flight abort test?

This article - https://futurism.com/spacex-blow-falcon-9-rocket-launch/amp - states that after 88 seconds, the first stage engines will shut down, and an automated abort command will be sent to the Crew Dragon Capsule.

It states engineers hope the Falcon 9 will explode mid-air.

Why do they think it will explode after engine shut down? Why does this not sound certain? If they do want it to explode, can they not fit a small explosive charge to make certain it does?

• "If they do want it to explode, can they not fit a small explosive charge to make certain it does?" That would seem to miss the purpose of a test! Jan 13 '20 at 10:35
• I'm pretty sure you must have read wrong. The loss of thrust will trigger the abort .That's the whole (or most of the) point of the test. no abort signal will be sent to the Crew Dragon!. The Crew Dragon abort system must detect loss of thrust and automatically start the abort sequence. If that wasn't the case what would be the point of the abort system? Jan 13 '20 at 11:34

After the pointy-shaped object leaves, the remaining blunt-nosed rocket will experience dramatically enhanced structural loading and possibly aerodynamic instability. They expect a "rapid scheduled disassembly" in flight, but if that does not happen they will either let it blow up when it hits the ocean, or blow it up as @RussellBorogove suggests if it violates termination criteria.

It's likely to undergo what SpaceX fans refer to tongue-in-cheek as a "rapid scheduled disassembly." In other words, it's going to break apart and/or explode over the Atlantic Ocean.

According to the final environmental assessment for the test filed with the Federal Aviation Administration, a Falcon 9 carrying the Crew Dragon will launch from Florida's Kennedy Space Center and fly for about 88 seconds before the test is initiated. Once the Dragon separates from the Falcon 9 first and second stages, the rocket is expected to become uncontrollable and break apart.

From the linked environmental assessment, and as @AI0867 points out:

The launch scenario where an abort is initiated during the ascent trajectory at the maximum dynamic pressure (known as max Q) is a design driver for the launch abort system.

Max-Q would also be the worst time for a powered rocket to loose its aerodynamic pointy-shaped nose.

The assessment continues:

2.1.9 BOOSTER DEBRIS DISPERSION

SpaceX anticipates a Falcon 9 breakup after Dragon abort. After thrust termination and abort separation, the Falcon 9 trajectory would be uncontrolled and would be expected to start departing from the nominal trajectory. In this nominal scenario, the propellant is expected to be consumed in the deflagration or aerosolized. This is consistent with behavior SpaceX observed in previous failures, including a Falcon 9 failure at their test site in McGregor, Texas, which failed at low altitude. In the event of an unanticipated and off-nominal condition, the following Falcon 9 breakup scenarios may be encountered:

• Off-nominal Scenario 1: Premature Falcon 9 failure results in an early abort, followed by aerodynamic breakup. Propellant is expected to be consumed similar to the nominal abort scenario.
• Off-nominal Scenario 2: Violation of autonomous flight termination criteria results in commanded destruct of Falcon 9, resulting in breakup of Falcon 9. Propellant is expected to be consumed similar to the nominal abort scenario. Dragon is anticipated to abort in this scenario. In general, failure cases are likely to result in an abort prior to an autonomous flight termination rule violation, as the abort triggers are more stringent by virtue of being designed to anticipate vehicle structural breakup from aerodynamic loads.
• Off-nominal Scenario 3: For early aborts where Falcon 9 velocity, and hence dynamic pressure, are still relatively low, if no autonomous flight termination rules are violated, Falcon 9 might impact the ocean’s surface intact. For aborts closer to the abort time frame, an intact impact is unlikely. In the event of Falcon 9 intact impact, propellant is expected to be consumed in the higher yield explosion resulting from propellant mixing upon impact.
• From the linked environmental assessment -> exactly. In these cases it's worth reading the primary source, second hand accounts often get the details wrong (because they are really really technical, not blaming anyone) Jan 13 '20 at 11:44
• Hmm isn't it an issue if the Falcon explodes unexpectedly early, before the Draco engines have time to move Dragon Capsule far enough? I know 0 about aerodynamics but I'm just worried that if aerodynamic forces against that blunt/plane head of the Falcon made it explode, this could happen earlier in the case of an accident,which could be fatal to crew in the capsule? Jan 20 '20 at 14:24
• For best results I think you can go ahead and ask that as a new question! I think that answers will explain that the situation is not as bad as you fear; the capsule's engines can start very quickly and because the LOX and RP-1'are in separate tanks they can't really detonate like a bomb, but if you post a proper question it will be easier for someone to post a full explanation. Thanks!
– uhoh
Jan 20 '20 at 18:48