SpaceX's billionaire founder, Elon Musk, says there'll be no quick answers to the questions surrounding Sunday's loss of his company's Falcon 9 rocket and its cargo for the International Space Station.

The cause of the mishap is "still unknown after several thousand engineering-hours of review," Musk tweeted overnight. "Now parsing data with a hex editor to recover final milliseconds."

He said that the problem was traced to excessive pressure in the upper stage's liquid oxygen tank — but that the cause of that condition appeared to be "counterintuitive." His comments led to deep discussions on such forums as Reddit and NASASpaceflight.com.

Launch failures are to be expected — and in a sense, this week's failure is less surprising than the fact that SpaceX had 18 successful Falcon 9 launches before Sunday's setback, including seven cargo deliveries to the space station.

"If you had told me at the outset of the Falcon 9 program that they would have 18 successful launches before their first failure, I would have told you that you were crazy," said Mike Gold, who is the director of Washington operations for Bigelow Aerospace as well as the chairman of the Commercial Space Transportation Advisory Committee, or COMSTAC.

At the same time, Gold acknowledged that the Falcon 9's first complete failure could hardly have come at a worse time.

Three failed launches

The other U.S.-based company sending cargo into orbit for NASA — Orbital Sciences Corp. — lost an Antares rocket and a loaded Cygnus cargo capsule in a fiery crash last October. The problem was traced to the Antares' Russian-built engine, and retooled rockets won't be available until next spring.

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Then, in April, Russia's robotic Progress cargo ship went awry after its launch to the space station — apparently due to a design flaw in the Soyuz rocket's upper stage. The Russians have since gone back to a previous configuration for that upper stage, and the rocket performed as expected during a satellite launch this month.

It's the very time for colleagues in the USA to think about the logic of their sanctions against Roscosmos. (cont) http://t.co/x5TQt4iDYR — Dmitry Rogozin (@DRogozin) June 29, 2015

Another cargo-filled Progress is set for launch on Friday. That resupply mission now looms as a potential turning point for the space station's fortunes. Right now, the crew has enough supplies to see them through late October, NASA space station program manager Mike Suffredini said. A successful Progress mission would add another month's worth of supplies.

Success would also clear the way for July's launch of three fresh crew members to the station, where they would join the three spacefliers currently on duty in orbit (including NASA's Scott Kelly, who's due to spend nearly a year in space). Failure would almost certainly force further delays in the crew launch, as well as a drastic reshuffle in the payloads for future robotic flights.

Critical months lie ahead

Japan's space agency is scheduled to launch its robotic HTV cargo ship to the station in August — and if that shipment were to be lost as well, the space station program would face some hard decisions.

"If you have no means to get supplies up at about 45 days before you get to zero, that's when we get into the process of planning the return of the crew. ... But we're not even close to that kind of conversation today based on the logistics we have on board," Suffredini said.

By October, Orbital Sciences and United Launch Alliance may be in a position to launch a Cygnus shipment to the station atop ULA's Atlas 5 rocket. And SpaceX may be back in business as well. The company's president and chief operating officer, Gwynne Shotwell, said she expected the investigation into Sunday's mishap to take "a number of months," but not as long as a year.

NASA and the National Oceanic and Atmospheric Administration confirmed that the mishap will have an impact on the launch schedule for the Jason-3 satellite, which is designed to measure global sea surface height. A Falcon 9 was supposed to launch the spacecraft on Aug. 8 — but now it looks as if that won't happen.

"While the incident review team looks into the cause of the mishap, NOAA and NASA are working with the European partners, CNES and EUMETSAT, to determine the next steps toward a new target launch date for Jason-3," NOAA said in a statement posted Monday.

SpaceX spokesman Phil Larson told NBC News in an email that it was too early to determine the specific impact that Sunday's mishap will have on future launches. "We are working with our partners to prepare for potential delays on the order of a few months. Once the root cause is identified, we will be able to better determine any changes to future launch dates, including Jason-3," Larson said.

Gold hopes the investigation is finished sooner rather than later. Bigelow Aerospace's inflatable space module was scheduled to go up with the next SpaceX shipment, which had been tentatively scheduled for September. The sooner SpaceX returns to flight, the sooner Bigelow's module goes into orbit.

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But Gold also emphasized that the investigation should be done right, and that the Federal Aviation Administration should be provided with all the funding that's needed to foster safe commercial spaceflight.

"Safety is the top concern," he told NBC News, "and we'll be ready when they are."