Nicodemus (nicodemusrat) wrote,

Antares Launch Failure

I was watching the Antares launch yesterday. Not in person but on a live NASA feed. I try to watch SpaceX and Orbital launches whenever possible. I was watching on Monday when the first Antares launch attempt got scrubbed because a sailboat drifted into the restricted safety area downrange. Then Tuesday...

The Antares is a relatively new craft so of course the possibility of a failure was something I considered -- more so than on other launches, anyway; it always goes through my head. Rocket science is challenging enough to inspire it's own saying, after all.

The sight was incredible. You've probably seen the footage on the news by now. (If not...) It had a clean lift off and first few seconds of flight before engine failure, after which the craft fell to the pad.

The good news is that this was an unmanned cargo flight and so no one was injured or killed. To overplay the contrast, that takes this from being a human tragedy to an engineering problem. And investigation of that problem started today, with examination of the launch site and wreckage.

Interesting Points Less Covered in the News

  • The Wallops launch site is surrounded by marshland. Rather than send in a fire crew at night they just let the site burn itself out.
  • The resupply mission was to the International Space Station. There's no risk posed to the crew there by loss of this vehicle. They have enough consumables to last about five months at present. Plus a Russian Progress resupply ship docked today. (That launch had been scheduled for a long time and was not in response to the Antares loss.)
  • The very first thing said by the Launch Director after the explosion was a reminder that all operators needed to stay at their consoles and ensure records and data were fully captured for the subsequent accident investigation. After some early NASA accidents, this has become a hard-learned lesson and such an announcement is the knell that you've entered into what they term "contingency procedures".
  • The Cygnus module carried a number of payload items including 18 science experiments from selected gradeschoolers. Read about one such student team.
  • Orbital Sciences is in the middle of a merger deal with Alliant Techsystems (ATK), one of the other aerospace launch companies, most well-known for the Delta rockets. ATK earlier acquired of Thiokol, the company which made the Solid Rocket Boosters for the space shuttle.

"What Caused the Failure?"

The press conference following the accident almost made me laugh at one point as the Orbital VP struggled to find new ways to say, "No, we don't know what caused the failure of our rocket only an hour ago. We actually need to investigate it thoroughly before we have a good answer. No, I won't blindly speculate for the press. Next question."

As someone unconnected, I'll feel free to speculate with the important caveat that it's entirely amateur armchair analysis. :)

Everyone is asking about the engines because it's clear in the video that there's an explosive burst from the aft of the rocket. Plus the Antares is powered by AJ-26 engines which have had failures during testing, including May of this year.

The AJ-26 is actually a refurbished Soviet-era engine known as NK-33. Orbital buys them from GenCorp subsidiary Aerojet Rocketdyne. Aerojet is refurbishing old Russian hardware (literally fixing up engine pieces built 40-45 years ago) and, due to problems, badly losing money on the deal.

Furthermore, Orbital had already decided to abandon AJ-26 engines and last year started looking for a new propulsion system, implying a drastic decision and extensive vehicle redesign work. Orbital has not announced what replacement engine it has selected but we know they considered "solid-rocket motors from ATK for the next block of Antares vehicles", which means the merger would make a lot of sense.

(If this were a spy novel or thriller, here's where the audience would realize the tragic motivation of the shady businessman at GenCorp/Aerojet, losing money and finding out his business deal has no future because his client is being wooed by another supplier, decided to take a drastic step...)

As a historical side note, the NK-33 engines (advanced for their time) were designed to power the Soviet moonshot vehicle, the ill-fated N1. This program's 5L launch failed about ten seconds after liftoff and crashed back to the pad in an eerie precursor of yesterday's event. The N1 accident in 1969 is possibly the largest non-nuclear explosion in history.

It is also, to be fair, likely entirely unrelated to the Antares accident except for those superficially similarities. But it's such an interesting historical footnote that I had to share it.

What I find most curious about the footage of the Antares launch failure is the motion of the vehicle. The first stage booster features two AJ-26 engines side by side, as seen here:

Watching the launch video, you can see the explosive burst from the aft of the vehicle around T+0:13, after which there's a clear loss of thrust. The vehicle stalls and descends.

However it does not tumble (at least while visible around the smoke and glare in the footage released which I've seen). The booster remains basically vertical as it starts to fall. This seems to indicate the failure was in a common component and the fuel feed system completely lost pressure; presumably, escaping RP propellant is what we're seeing in the growing fireball. This would point to the failure not being in just one engine (where the other could continue operating at least for fractions of a second and impact torque) but something in the aft tank, feed flow plumbing, or front of the turbopumps.

So what happened? As they said at the press conference, we'll have to wait for a proper investigation. I'll be quite interested to learn, though. Perhaps the storied record of the AJ-26 will prove a red herring and something in the adapter to the booster tanks was to blame?

In the meantime, sympathies for the Orbital staff who've had to take this blow.

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