Register for an account

X

Enter your name and email address below.

Your email address is used to log in and will not be shared or sold. Read our privacy policy.

X

Website access code

Enter your access code into the form field below.

If you are a Zinio, Nook, Kindle, Apple, or Google Play subscriber, you can enter your website access code to gain subscriber access. Your website access code is located in the upper right corner of the Table of Contents page of your digital edition.

The Sciences

Falcon doom found: a whisper of thrust

Newsletter

Sign up for our email newsletter for the latest science news

Elon Musk of Space X has released the news of what happened to the Falcon 1 rocket that failed to reach orbit last week.

The problem arose due to the longer thrust decay transient of our new Merlin 1C regeneratively cooled engine, as compared to the prior flight that used our old Merlin 1A ablatively cooled engine. Unlike the ablative engine, the regen engine had unburned fuel in the cooling channels and manifold that combined with a small amount of residual oxygen to produce a small thrust that was just enough to overcome the stage separation pusher impulse. We were aware of and had allowed for a thrust transient, but did not expect it to last that long. As it turned out, a very small increase in the time between commanding main engine shutdown and stage separation would have been enough to save the mission.

In other words, the stage separation didn't happen because the mechanism that splits the two stages was still feeling thrust from a little bit of leftover fuel the pneumatic pusher that physically pushes the two stages apart is rather weak. It works, but the still-accelerating first stage overtook the too-slowly moving second stage, so the separation didn't work. (My thanks to a mole at Space X for correcting my misinterpretation; and if it's still wrong it's my fault not his/hers). That mechanism needs the rocket to be coasting, not accelerating, so it didn't work. Without stage separation, the rocket couldn't go up anymore, and it fell back to Earth.

spacex_falcon1_3.jpg

Musk goes on to say they are confident they understand the problem, and can solve it by simply waiting a little longer after first stage engine cutoff before separating the stages. That should allow the extra propellant to burn off. The fourth Falcon launch is already prepping, and may happen as soon as September.

    2 Free Articles Left

    Want it all? Get unlimited access when you subscribe.

    Subscribe

    Already a subscriber? Register or Log In

    Want unlimited access?

    Subscribe today and save 75%

    Subscribe

    Already a subscriber? Register or Log In