What does six times the weight of gravity feel like?

I ticked off another step in my space readiness program with the completion of G Force training at the NASTAR facility in Philadelphia last week.

We’ll experience G forces on both the exit and the re-entry to the earths atmosphere, and the experience can be pretty intense given re-entry involves six times the weight of gravity pushing down on you,  so I was very keen to make sure I could manage it well before the time I actually make the trip –  it would be a real shame to black out on the way up and miss half the experience!

There are two kinds of G forces we’ll experience on the trip to space, one which is essentially head to foot – Gz – and one which is chest to back – Gx. This pic gives a bit more of an illustration of the two.


Gz is the one more likely to make you black out, as it pushes the blood from your head down into your lower body. The way you combat that is to essentially clench your entire lower body, stopping the blood from draining down. But as you’ll quickly realize if you try it at home, as soon as you breathe you loose the muscle contraction, so you need to combine the clench with a breathing technique that allows you to take quick sharp half breaths while keeping the contraction.  We did all the theory, and practised it in the training room but then it was time to put it to the test in the giant spinning centrifuge.

That first simulation was pretty nerve wracking, as none of us really knew what to expect from the experience. We’d seen the capsule  spinning at high speed from the viewing room, and it was hard to imagine anything other than extreme dizziness.


The inside of the simulation cabin

I stepped up into the capsule and strapped in for the first time, going through the familiarization and briefing checklist before the door closed and I sat waiting for the trainer to take his place at the monitor, where he talked me through the simulation. His calming voice in my ear was invaluable, as he reminded me of all the steps we’d just covered in the theory.  Having just watched someone else do the same thing, I knew the other 5 trainees were waiting in the viewing room, with full visuals and audio showing exactly what I was experiencing. The below photo is a screen shot of what they saw as I waited for the first simulation, with the nerves pretty apparent on my face!


Interestingly once the capsule starting moving I couldn’t feel the circular motion at all, it was purely a vertical sensation. If you relaxed your muscles at all you could immediately feel the blood starting to drain away from your head, which was a great reminder to keep them clenched!  The first simulation took us to around 2Gz (2 times the usual force of gravity) and the second one ratched it up to 3.5Gz, which was pretty intense.  Once you get above 4-4.5 you really need a G suit, which does the compressions for you, but we won’t be wearing those and our ride to space will see us experience between 3 and 3.5Gz on exiting the atmosphere.

Time for lunch, and I was absolutely starving after the adrenaline rush the intense experiences of the morning generated.  One of the learnings I’ll be taking away is I definitely want Stuart and the kids to have snacks waiting for me when I get out of the spaceship!  We all compared our crazy G-face photos and headed back into the class room to learn about how to manage the Gx forces.

This was the one I was a bit more concerned about given I get asthma, albeit very well controlled.  I had to do a full medical before being approved to do the training, but it’s still a little confronting to wonder how you’re going to feel with 6 times your own body weight pushing down on your chest.  It was something I definitely wanted to test out and see how I coped while I was on the ground with a stop button to push rather than 100km above the earth!

I was pretty nervous climbing into the capsule this time, reminding myself it was all about shallow breaths through pursed lips, as if I was breathing through a straw. The first simulation took us up to 3Gx, which is essentially three times your body weight pushing down on you.  Surprisingly I felt it more through the face than the chest, my skin was dragged back so tightly I felt like I was living through a facelift without anaesthetic (but sadly with no residual after effects!).   6Gx was tougher, but again I think I was so distracted by the feeling of my face pulling back it took any of the stress out of the chest pressure and I didn’t have any trouble completing the simulation.

6G face!
Grinning like a fool after conquering the G’s

The second day was all about putting the two together to experience what the actual space flight itself will be like, with this image illustrating when the G forces kick in at different points in the journey.


Our training today would simulate the flight profile, with a combination of Gz and Gx forces in the launch, and then strong Gx forces in the re-entry.  It was the first time we would combine the two, and we worked through the theory first which included how to quickly switch from the muscle clenching techniques of the Gz force to the ‘breathing through a straw’ Gx management.  We would be doing do two flights, one simulating 50% of the force experienced and then the second at full force.


As well as replicating the forces experienced, the screens in the cabin replicated the visuals we’d be seeing as we left the earth behind and headed up into space.  It made it all so very very real, and I loved every minute of it, as you can see in the video of the experience here.  Unfortunately it doesn’t show what I was seeing, but gives a pretty clear indication of how much fun I was having!


I’ve now officially got my wings (Did I mention we got given flight suits to wear throughout the experience? I couldn’t get the Top Gun theme song out of my head the entire time I had the suit on…) and I’m more excited than ever about making the trip to space.  I now know I can handle the G’s, so when the time comes I can just sit back, enjoy the ride and make the most of every minute.  In the meantime though, I want to keep on enjoying every fantastic experience that Virgin Galactic keeps delivering along the ‘journey to the journey’.



Older Story:

The Power of Vulnerability

September 21, 2017

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