As of 26 April 2019 SpaceX has accidentally lost two of their block 5 boosters, which are supposedly capable of 10 flights with minimal refurbishment and 100 flights total. [Actual best achieved turnaround time is 75 days including refurbishment.]

And of course Crew Dragon catastrophically exploded.

Additionally, the second stage of the launch vehicle for SpX CRS-7 ruptured during ascent, causing the loss of the launch vehicle and payload, and the second stage of the launch vehicle for AMOS-6 exploded during fueling in preparation for a static fire.

On 28 June 2015, SpX CRS-7 experienced a failure near or involving a Composite Overwrap Pressure Vessel (COPV) containing pressurization helium – during the accident investigation it was found that the struts holding the COPVs in the upper stage LOX tanks were constructed of a stainless steel that was not rated for cryogenic conditions. SpaceX had assumed that using more material than strictly necessary going by the non-cryogenic rating would grant an adequate margin. It was found that this was not the case, and the struts were presumably changed to an appropriate, cryogenic-rated material.

However, another possible cause of the SpX CRS-7 failure is COPV rupture, which would overpressurize the LOX tank and rupture the upper stage. NASA’s investigation could not rule this out, but SpaceX declared that the struts were the problem and returned to flight.

On 1 September 2016, a COPV ruptured in the LOX tank of the upper stage on the launch vehicle for AMOS-6, bursting the stage and causing the destruction of the vehicle, payload, and launchpad structures. The immediate fix was to adjust the helium loading procedure, with NASA requiring the development of new COPVs to meet commercial crew safety requirements.

The COPVs that SpaceX were/are using have a metallic liner and a carbon and resin overwrap, similar to the Kevlar and resin overwrap COPVs storing pressurization helium on Shuttle, which flew on 135 flights without causing a destructive issue:

STS justification for flight – kevlar overwrapped COPV

STS COPV test

To tie this back to the most recent explosion, it is apparent that an energetic event occurred inside of Crew Dragon, resulting in the release of the Launch Abort System (LAS) and Reaction Control System (RCS) propellants. These propellants are stored in tanks and pressure fed into the combustion chambers by helium contained in COPVs very similar to those that failed earlier. This is the third catastrophic explosion occurring in the vicinity of a high pressure helium system on a SpaceX vehicle, which is notable because no other entity involved in space travel has catastrophic problems with high pressure helium, despite nearly universal use.

So, why is SpaceX struggling with issues that are well within the state of the art? Who knows, but they certainly give the impression of doing substandard work as fast as possible. The most time-consuming part of any highly scientific enterprise is the work of characterization, in this case the characterization of spacecraft and launch vehicle response to modeled stresses. High fidelity testing is necessary to validate the original design assumptions – merely answering the question of “did it blow up or not?” is insufficient, especially when designing for crew.

I encourage you to do some research into ‘normalization of deviance,’ especially as it relates to the two Shuttle disasters – vehicles can be pushed beyond the associated engineering and testing work with some success, but eventually reality catches up.