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Lots of detailed news from Carmack's crew. Good read. Here are some key points;
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We made the decision to not bother testing the hotter engine before XPC, and just go with the flight-tested pattern. We have dropped 20 pounds off the vehicle since we did the 192 second flight, and that wasn’t to complete depletion, so we have 200+ second capability as-is, which should be plenty for the 180 second level two flights. My wife scolds me sometimes about not just sticking with a working solution, and she is usually right.
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We brought out Texel, our second Quad vehicle, and propagated all the updates we have made to Pixel over. We are in the process of making sure that our team skill sets are fully redundant, so I started training Russ on running the laptop flight control software to fly the vehicles (Joseph is also training Phil on driving and operating the crane truck). We went out for a tethered test, but we managed to get a bit of a bang on startup, which cracked the graphite chamber.
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To address each of the issues we believe led to the startup bang (which wasn’t much as hard starts go, not damaging any metal, but the graphite is fragile), we are now doing the following:
We are back to 300 psi minimum pressure. The engine cough doesn’t seem to hurt anything, so we are going to stick with what has been demonstrated to work. We will eventually have to revisit this for in-flight restarts, which will always be at a lower pressure. We may need to have a different idle throttle position based on current tank pressure, but we will work that out post-XPC. We are going to bleed fuel into the igniter early in our flight prep process to make sure it is going to instantly get fuel during the start sequence. I have made the lox pre-chill part of the automated start sequence, so it will be exactly the same duration on every start.
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Now that we have proven that the module works as designed, we are going to build up the remaining four modules that we have parts on hand for. James is going to work almost full time on the fabrication work, so I wouldn’t be surprised if we have the tank sets bolted together next month. All the plumbing, wiring, and testing will take more time, but I’m pretty sure we will have a four module system done for display at XPC. A tethered test at XPC might be possible, but winning the Lunar Lander Challenges is the main priority. Again, it is a little unfortunate that our development scheduling gets hampered by the fixed scheduling of the LLC at the XPC.
The four module vehicle will probably be flying the Space Diving mission next year. If we don’t wreck it in testing high altitude flight, we are considering doing a staging demo, flying the fifth module off the four module cluster, which would be a solidly 100km+ vehicle. The commercial manned 100km vehicle should be a cluster of six to nine improved modules (higher mass ratio and aspect ratio) in a single stage for full redundancy, with a nice cabin on top.
We made the decision to not bother testing the hotter engine before XPC, and just go with the flight-tested pattern. We have dropped 20 pounds off the vehicle since we did the 192 second flight, and that wasn’t to complete depletion, so we have 200+ second capability as-is, which should be plenty for the 180 second level two flights. My wife scolds me sometimes about not just sticking with a working solution, and she is usually right.
>
We brought out Texel, our second Quad vehicle, and propagated all the updates we have made to Pixel over. We are in the process of making sure that our team skill sets are fully redundant, so I started training Russ on running the laptop flight control software to fly the vehicles (Joseph is also training Phil on driving and operating the crane truck). We went out for a tethered test, but we managed to get a bit of a bang on startup, which cracked the graphite chamber.
>
To address each of the issues we believe led to the startup bang (which wasn’t much as hard starts go, not damaging any metal, but the graphite is fragile), we are now doing the following:
We are back to 300 psi minimum pressure. The engine cough doesn’t seem to hurt anything, so we are going to stick with what has been demonstrated to work. We will eventually have to revisit this for in-flight restarts, which will always be at a lower pressure. We may need to have a different idle throttle position based on current tank pressure, but we will work that out post-XPC. We are going to bleed fuel into the igniter early in our flight prep process to make sure it is going to instantly get fuel during the start sequence. I have made the lox pre-chill part of the automated start sequence, so it will be exactly the same duration on every start.
>
Now that we have proven that the module works as designed, we are going to build up the remaining four modules that we have parts on hand for. James is going to work almost full time on the fabrication work, so I wouldn’t be surprised if we have the tank sets bolted together next month. All the plumbing, wiring, and testing will take more time, but I’m pretty sure we will have a four module system done for display at XPC. A tethered test at XPC might be possible, but winning the Lunar Lander Challenges is the main priority. Again, it is a little unfortunate that our development scheduling gets hampered by the fixed scheduling of the LLC at the XPC.
The four module vehicle will probably be flying the Space Diving mission next year. If we don’t wreck it in testing high altitude flight, we are considering doing a staging demo, flying the fifth module off the four module cluster, which would be a solidly 100km+ vehicle. The commercial manned 100km vehicle should be a cluster of six to nine improved modules (higher mass ratio and aspect ratio) in a single stage for full redundancy, with a nice cabin on top.