X-Prize Cup

Well, now that I’m back from Las Cruces, I figured it might be good to wrap up the Masten Space Systems X-Prize Cup 2006 saga, picking up where I left off.

Before I go into the more detailed story, I’d like to thank the X-Prize Cup people, and particularly our pad manager Alan Perryman and our safety officer, Vince Hill. Alan and Vince were extremely professional, and were a lot of fun to work with. They’ve got a standing invitation to come out and join us for a test whenever they want. The rest of the X-Prize Cup volunteers gave it their best, and at least by the end of Friday had really hit their stride. Thursday and Friday morning were a little bit rough around the edges, but they came through for us in the end.

Anyhow, Thursday, the weather was much nicer, and we set about getting the trailer ready for the show. We made a quick fix to the PLC code (to deal with potential network issues–which turned out to be a really prescient decision) and then ran the test cases to verify that the thing did exactly what it was supposed to do (both nominally and in emergencies). We then spent most of the rest of the morning waiting for clearance to take our trailer out to the firing area. We were told that starting at 2pm there would be a two hour window in which we could do as many firings as we wanted to. We were hoping to get the trailer out there sufficiently before 2pm so that we could have it setup, loaded, and ready to fire as soon as the airfield was closed. We really didn’t anticipate being so much further ahead of the game that we’d have time to sit around and chat.

As it is though, that was rather fortuitous, because we got to speak with some rather interesting people, such as Professor Yoshifumi Inatani of JAXA who helped manage their RVT program. He recognized the landing gear concept, was obviously flattered to hear that we borrowed our throttle control algorithm from them, and generally liked our approach. If I understood him correctly, it sounds like they are investigating another generation of RVT that has a 4-engine design similar to ours–since it allows you to have engine-out functionality (and also makes relights for landing less dicey).

Unfortunately, our preparation day didn’t end up going as smoothly as we had hoped. Mostly due to the kind of logistics problems to be expected when trying to organize such a complex show with a mostly volunteer force. Simple stuff like miscommunications leading to getting the wrong size, number, and pressures for our pressurant gas cylinders. We’ll just have to make sure next year that we are more thorough in our advanced coordination. In the end, due to delays waiting for people at the fueling depots, and other such, we were able to leak check our system, test the igniters, and reinsulate all the lines, but were told to clear the field before we had a chance to fire the engine even once. We really didn’t want to have our first engine firing after that long of a road trip be in front of several thousand people, but we did our best with the situation we had.

That evening my parents arrived with my four youngest siblings, and the whole team ended up going out to dinner with them (along with Richard Wills, the pad manager for Armadillo’s flights). The Mexican food was good, albeit a bit spicey. It was nice having them there, I was really surprised with how interested my dad was in the whole alt.space thing. He’s an Electrical Engineer of sorts by training (worked at HP for 12 years or so), but apparently he had a little bit of the space bug in him after all.

Friday morning we had to be at the airport at 5am. It was cold, it was early, and we were all quite tired. It was kind of cool getting to see the Armadillo guys off from the propellant depot. Those guys are good friends of ours, and I was glad we had a chance to wish them luck. While we were chatting with them, John was mentioning the issues with his wireless communications that others have talked about, and I was rather glad that we had made the software tweak on Thursday that we did. As it is, that’ll be something we’ll need to make sure we deal with for next year.

After seeing them off, we were able to load up and get out to our site. We got our stuff setup, and ready to fire over an hour early, going meticulously through every possible thing on the checklist (and adding a few paranoid precautions on top of that). As it is though, we ended up waiting for over two hours from when we were ready to go to when we got the go-ahead to load LOX and light the thing off. We had been planning on doing two short firings to verify the throttle positions for our engine (and to make sure nothing was wrong), and then go on to a 30 second firing. Unfortunately, right after the two short firings, we were told to stand down for an F-117 flyby. After the flyby was over we weren’t given the opportunity to finish our 5 minute session. There was also apparently some confusion on the media side, and the Jumbotron ended up looking at someone else’s hardware, and apparently they had no idea that we were planning on doing to short firings first, and thought that we had had some sort of engine failure.

Fortunately, the X-Prize people got more into their stride by the afternoon. We went out, and had a picture perfect 30 second firing. I got it on video, and it was so rock-solid stable that the only clue that you weren’t looking at a still photo of the shock diamonds was the slight vibration of the camera, and the violent flapping of the weeds and bushes in front of the engine. They announced it better too. We were hoping to do a quick relight after that, and do another long firing (to tank depletion–probably another 60 seconds), but one of our sensors on our stand informed us that the heat soak was bad enough that the igniter IPA valve was outside of its operating temperature, so we decided to not chance things. We don’t need relight capabilities quite yet, so we hadn’t gone out of our way to get higher temperature solenoid coils and plungers, but that’s something we’ll probably take care of before we fly anything that needs the relight capability. We’d rather have a flawless day than to push our luck in front of a crowd.

While we were up to that, there were lots of other things going on. Stuff like Rocket Belt flights, an Armadillo flight attempt, some Tripoli launches, some Rocket Truck and Rocket Bike firings, and some other flybys of various sorts. All in all a good day. Between our two firing sessions I also got to man the booth a bit. Met some commenters on the blog (including Ferris Valyn), some other bloggers (Dan Schmelzer of Carried Away), as well as several former DC-X guys. I think I also got to speak with some of Anouseh Ansari’s relatives (though Robin Snelson didn’t actually introduce them that way), and got to chat with some of our other friends in the industry. Didn’t get to meet “Mr X” of the Chairforce Engineer blog, or Josh Gigantino, or Elon Musk. But you can’t win them all I guess.

The rest of the day was a blur. I managed to pull myself away from things a bit once or twice to go look at displays, but what with being rather stressed out about our testing, I don’t recall a whole bunch of it. Going all day on just one muffin and a small thing of Orange Juice probably didn’t help either. My family took off early in the evening, and I think I ended up crashing out fairly early (I can’t remember now).

The next day was just as early, and I was even more sleep deprived. We once again got to see the Armadillo guys off from the propellant depot area. They had managed to patch their vehicle together in time for another day worth of flight attempts. We were all pulling for them.

Things on the field went a lot smoother on Saturday. Apparently things had been figured out so that they didn’t have to evacuate us off the field for every single Tripoli flight or static firing. So we got to watch some Tripoli flights from close by, as well as Armadillo’s flight off in the distance. Our firing in the morning went picture perfect. We had topped the LOX tank all the way up (literally), and openned a big ol’ can of hot flamey stuff. 94.3 seconds of some of the most stable hot flamey stuff I’ve ever seen. Ran the LOX tank all the way to depletion. It was a sight to behold. The only fly in the ointment was that when I went out to the camera, it turns out the film had run out only a few seconds before ignition! The longest firing our company has had to date, and one of our best shows yet, and the camera decides to run out of film. What are the odds?

After that firing, we got to spend a bit of time back at the booth, and checking out some of the other displays. I stopped by the Rocketplane/Kistler booth and chatted with some of the guys there a bit, visited our friends at Frontier Astronautics, chatted with Steve Harrington of Flometrics, and had a run-in with Korey Kline of eAc. He didn’t believe our Isp numbers we’re quoting for the engine (240-250s on the high end), and more or less questioned our integrity or competence. He said “we’ll see when you actually try to fly it how much performance you really get”. Indeed.

Still didn’t get any lunch on Friday. Too nervous. We ended up heading out to our test site right after Armadillo flew the first leg of their third prize attempt. We didn’t hear about the broken leg until afterwards. We got our test trailer setup again for firing. This time we were going to take a bit of a risk and try to do two short (3 second) firings to tune in the engine at a lower throttle setting, and then go after a 120-180 second firing if we could find a stable low throttle setting soon enough. Right as we were about to start LOX loading, Armadillo had their accident. From where we were standing we were worried they had popped another engine. We were really bummed out for those guys, and the thought hadn’t sunken in yet, that that meant both prizes were going to be wide open for next year. After the fire at their site was out, and the emergency over, we went to load LOX. It turns out that the dewar didn’t have quite enough left in it for a full tank of LOX this time, but we figured that’d be ok with a long half-throttle run. Who’s really going to pick nits about the difference between a 150 second firing and a 180 second one?

Then we got a call from flight ops that the Masten team and the Orion team were to clear the field–the show people felt there was only enough time for one thing left, and felt the Tripoli launch would be more important. We were really crushed, but followed orders and headed back to the flight line. We were only something like 1 minute away from being able to start our routine, and the Orion guys were also only a few minutes away themselves. Ian walked off in disgust. Just when we were about to abandon hope of getting a last firing in, one of the Orion guys brought up an interesting point. Apparently their truck was loaded with Nitrous, and the detanking system for their truck was slow enough that it’d take 3 hours for them to completely safe the truck if they didn’t fire. Since the truck is considered hazardous until all the oxidizer is out of it, the airfield would’ve been forced to remain closed for another three hours if they didn’t empty the nitrous tanks the “right way”. Needless to say, between that fact, and the fact that both of our teams were within 5 minutes of being able to fire our engines, we were able to persuade them to see things our way.

I ran off and grabbed Ian, and we jumped into Dave’s truck as soon as the Tripoli launch was done. We raced out there, repressurized the stand, and had every ready to go within about two minutes. We decided to just bump the settings back to what we had used for the previous firings (with the LOX setting bumped down one notch since we only had a partial tank, and since the smaller helium bottles they had given us were also already at much lower pressure than we usually liked). We were informed that the Orion guys would fire first, then we would get a 15 second countdown, and then we’d get to fire. The orion truck went off right on time, and then when our time came, we pressed the button and held our breath. At least for the first few seconds–holding your breath for 74 seconds isn’t highly reccomended. The X-Prize Cup guys came through in the end, and Orion and MSS delivered a grand finale.

Well, ok there was that F/18 flyby (which passed only about 50 feet directly over our heads–I’ll post some pictures when I have them), but that doesn’t count. It ain’t a rocket.

After we packed up, and headed back to the propellant depot, I bumped into one of our friends from XCOR. Due to the helium tanks starting off so low, we ended up getting some feed-system coupling induced instability toward the end of the run. Apparently the XCOR guys had been worried that our engine was going to come apart if we didn’t shut her down. When our pressurant system does it’s job the engine runs just fine, but I also like knowing that we build our engines robust enough that they can take even a fairly roudy combustion instability and just keep on running. Belt/Suspenders/Duct-Tape as Randall would say.

After hauling our trailer back, offloading the propellants, and taking the trailer off of Dave’s truck hitch, we headed back to speak with the Armadillo guys at their staging area. I asked Russ what had happened, and he told me about the landing gear leg breaking off, and their attempt at a return flight. I was really disappointed that they didn’t manage to walk away with some prize money, but they seemed to be taking it in stride. Their flights had been amazing to watch, and for this being their first four times trying to fly the thing off the tether, and their first times trying to do horizontal translations and ground landings, I think they did fairly well. As John said, if they had had another day or two, they probably could have patched things up and pulled it off, but it looks like it’ll be next year before they try again.

Randall, who had been their safety officer, looked beat. I told him that he looks like he got himself some more grey hairs this last week, and then quickly added that I think I had earned myself a few as well.

After most of the people had had a chance to congratulate John, and take pictures, I commented to John that it looks like we’d have to give him some competition this next year, and he replied “Yeah, we’ll make you guys work hard for second place”, and then jokingly said that he was “throwing down the gauntlet”. We’ve got a long way to go, and only a year to do it in, but I really hope that we can be out there next year flying our vehicles too. I’m looking forward to the flyoff.

Anyhow, the rest of the evening also went pretty cool. Dave and I were with the Armadillo guys, when they let us in to take some Armadillo team pictures in front of the LEM hardware. They let us take some pictures from up close, which was kind of cool. Definitely an interesting design, though I’m sure that with 50 years of technology improvement, we could do a lot better. Alas, NASA seems not to have learned all the right lessons yet, so it may very well fall on the private sector to do the job right.

The end of the evening was a party hosted by the Space Frontier Foundation guys. I don’t drink, but I figured it’d be fun to hang out with the rest of the guys anyway. At the party they announced the newly selected SFF “Advocates”, and was pleasantly surprised to find that my boss Dave had been selected, as was Steve Harrington, and several others. I also found out that Ed Wright’s company suffered a serious blow last week, when their camera chase plane crashed killing all 5 on board. I wanted to say something to Ed, but what can you say in a situation like that? It turns out that had he not made a last minute change in plans, he would’ve been on the plane that went down. That’s a truly awful piece of bad luck, and I hope that Ed can recover.

Anyhow, after that and a brief meeting with the Frontier guys and the rest of our team to go over what our plans were to get this vehicle in the air, we called it a night. Sunday morning we packed out with the help of Armadillo’s crane truck, and we drove the rest of the way back to Mojave that evening, arriving shortly after midnight.

Now that I’m back, we’re in the process of putting together our plans for next year. Things should be rather interesting. John’s team only has to make a few improvements (mostly better landing gear design) in order to have a good chance at Level One, so I hope they focus on that. It’s going to be a real challenge, and the logistics side of things will need a lot of improvement, but it should be a load of fun.

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Jonathan Goff

Jonathan Goff

President/CEO at Altius Space Machines
Jonathan Goff is a space technologist, inventor, and serial space entrepreneur who created the Selenian Boondocks blog. Jon was a co-founder of Masten Space Systems, and is the founder and CEO of Altius Space Machines, a space robotics startup in Broomfield, CO. His family includes his wife, Tiffany, and five boys: Jarom (deceased), Jonathan, James, Peter, and Andrew. Jon has a BS in Manufacturing Engineering (1999) and an MS in Mechanical Engineering (2007) from Brigham Young University, and served an LDS proselytizing mission in Olongapo, Philippines from 2000-2002.
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20 Responses to X-Prize Cup

  1. John Carmack says:

    >He didn’t believe our Isp numbers
    >we’re quoting for the engine
    >(240-250s on the high end)

    FWIW, I don’t believe those numbers either. 🙂 I don’t think 250s is even theoretically possible at your chamber pressure.

    If you can hover the 1.32MR XA0.1 for 57 seconds, you have a delivered 200 Isp. I will be rather surprised if that happens after startup / shutdown transients, steering losses, residual propellants, throttling losses, etc. Of course, you can easily slim the weight down and get significantly longer runs.

    John Carmack

  2. dave w says:

    So what’s the theoretical performance of LOX/IPA at standard calculation conditions (1000/14.7 psia; optimum O/F; shifting)?

    (I’m not saying that’s the conditions MSS runs in their engines, but it’s a convenient standard for comparison with published figures which frequently are calculated at that operating point.)

    I’d run a calculation myself, but the software I’ve been using (ISP.exe from dunnspace.com) doesn’t include the alcohols in its propellant table.

    One way or the other, John C’s comment looks like a potential precursor to an interesting discussion…

  3. Jon Goff says:

    John,
    FWIW, I don’t believe those numbers either. 🙂 I don’t think 250s is even theoretically possible at your chamber pressure.

    Actually, it is. At our chamber pressure and expansion ratio, theoretical frozen performance is around 267s, and shifting is about 271. Once you factor in backpressure losses, we’re still only getting in the mid 90s as a percent of theoretical Isp. Now, if we ran at the chamber pressures and expansion ratios you guys tend to use, the frozen and shifting Isp drops to about 212-213s (but now that you’re underexpanded, you get a little Isp back from having higher pressure at the exit plane than ambient). That pressure and expansion ratio makes a big difference. At least from the numbers I got a while back, when you factor in all the losses, you guys are getting in the high 80s to low 90s of the theoretical Isp at your chamber pressure and mixture ratio for your higher end engine, so the fact that we’re doing a little better when we took a more methodical approach shouldn’t be that much of a surprise.

    If you can hover the 1.32MR XA0.1 for 57 seconds, you have a delivered 200 Isp. I will be rather surprised if that happens after startup / shutdown transients, steering losses, residual propellants, throttling losses, etc.

    Yeah. For XA-0.1 one of the bigger losses is the backpressure losses. At our expansion ratio (since we were originally designing the vehicles with a suborbital flight in mind–not long duration low altitude hovers), Isp drops down quite a bit at the lower throttle numbers. Residuals, steering losses, transients etc, all do add up quite a bit for a vehicle with as low of a mass ratio as we’re dealing with. If we get 45 seconds, I’ll feel glad. There’s a reason why we decided to go with larger tanks on XA-0.2. We could seriously go with about 1000-1200lb of propellant before the engines start getting close to maxing out.

    Of course, you can easily slim the weight down and get significantly longer runs.

    Yup, that and increase the propellant capacity. Or make nozzles with smaller expansion ratios for low-altitude ops.

    ~Jon

  4. kert says:

    Re Japanese RVT guy, i believe that would be Prof. Yoshifumi Inatani

  5. Jon Goff says:

    Kert,
    Bingo! That’s the guy. I corrected my blog post with the new info.

    ~Jon

  6. Josh Gigantino says:

    I stopped by the Masten display a couple of times, but you must have been busy being a rocket scientist. My Postcards To Space booth went great, lots of contacts, new friends and some sales. Rode the “VR Skydive” wind tunnel a couple of times and learned a lot.

    You can read a review of my experience here:

    uplink.space.com

    How about a bunch of us get together next year and go find a petroglyph site for an afternoon? There’s at least one near White Sands.

    How many of the teams had RVs in the lot? Is that the best way to do this, so that you have a mobile base?

    Josh

  7. ザイツェヴ says:

    This is very trivial, but has to be said. Be sure to get a digital camera with CF (I have Canon EOS 350, and keep extra cards in case’s pocket just in case I max it) and a pocket digital camera for shots of opportunity. Of course you still can run out of capacity or drain your battery…

  8. Jon Goff says:

    ?????,
    I actually did have a digital camera, I just accidentally forgot to pack it. Some of the others got a bunch of pictures though, and once we have those uploaded, I’ll either post them here, or at least post links.

    ~Jon

  9. Jon Goff says:

    Josh,
    Sorry I missed the opportunity to meet up with you. We were out at the test site a lot this year, and will likely be out at the pad almost the full time next year too. I read your uplink post. It was a good read. As for RVs, we didn’t have anything so fancy this year, though we’ll probably have some sort of MSS-specific vehicle next year.

    As for the petroglyphs, that’d be a lot of fun, but if this year was representative, it’d have to be after things were over at the XP Cup. But make sure to ping me next year a couple weeks prior to the event.

    ~Jon

  10. Paul Breed says:

    Based on cpropep
    To get 267 ISP frozen at sealevel needs more than 550 psi of chamber pressure. As this is a pintile engine with no film cooling, the mixture ratio could be very close to ideal.
    Also the XPC in New Mexico is above sealevel for a tiny bit of gain.

    You can see my theroetical ISP tables for a variety of propellants at:
    http://www.rasdoc.com/paul/rockets/ISPTable.pdf

  11. K2unit says:

    Jon,

    I’d hardly call our meeting a “Run-In”… more like a “A Frank & Honest Discussion”!

    I said your current vehicle was too heavy and your propellant fraction was to low. As I recall you said the propellant fraction was 20% and that you wanted it heavy for throttling issues.

    I said I thought it was a mistake to have four engines and also spaced so far apart rather then a single chamber. You explained they all had single axis gimbling and throttling and explained your philosophy of developing a very high reliability lower thrust chambers and clustering them.

    I said you’re never going to have a 10,000 lb rocket fly to space, multiple times in a day, built and flown in 18 months like your web site states. You said talk to the marketing department.

    Regarding my thoughts on your Delivered Isp…Carmack’s comment says it all.

    Towards the end of our discussion I did compliment you on building actual hardware and doing actual testing unlike 80% of the Xcup presenters. I commented how gorgeous your hardware was and that hardware is the only thing that matters and you were way ahead of the curve!

    Having said that, I do have a prediction….
    There will be no serious competition to Armadillo next year.

    With the amount of building and testing your team is doing, over many many others, Masten Space is certainly a team to watch! You just have to make sure that your Marketing & Press Releases don’t group you with all the other space companies making unbelievable claims!

    Good talking with you & Keep up the good work!!!!

    K2

  12. Jon Goff says:

    Paul,
    You’re right that to get 267s frozen with the nozzle outlet at sealevel would require a bit higher pressure. We’re a little bit overexpanded at sealevel, and I didn’t include the backpressure Isp losses in that quick reply. But even with the backpressure losses, we’re still well within the realm of reality.

    500psi P/C with ideal mixture ratio, and our expansion ratio, with back pressure losses yields: ~259s frozen at sea level, and 262s shifting.

    Of course, those test results were not at sea level, so the theoretical shifting and frozen were probably closer to…..somewhere between 260s frozen and 264s shifting, to maybe as high as 261s frozen and 264.5s shifting.

    Anyway you slice it though, we were making somwhere between 92-96% of the theoretical Isp. While pretty good, that’s not ridiculous at all. The numbers I recall getting for Armadillo on their high performance design were in the 88-90% range.

    Oh, and one other thing that might also make a difference, is that some of the nozzles we had had throats that were on the small side of our tolerance, which meant that 500lbf occured at slightly higher than 500psi chamber pressure. If chamber pressure were say…520psi, it would make our numbers even more reasonable…

    I guess I just don’t see what all the disbelief about our numbers are. If you believe Armadillo is really getting 210s with their high performance engine, it’s totally reasonable to believe that an engine with almost twice the chamber pressure and over three times the expansion ratio should get a much better Isp.

    ~Jon

  13. Jon Goff says:

    Korey,
    I’d hardly call our meeting a “Run-In”… more like a “A Frank & Honest Discussion”!

    Fair enough. I was probably being at least a bit melodramatic.

    I said your current vehicle was too heavy and your propellant fraction was to low. As I recall you said the propellant fraction was 20% and that you wanted it heavy for throttling issues.

    Exactly. Propellant fraction on XA-0.1 sucks because it was never built for performance, or intended for competition in the LLAC. It was only meant as a take-off and landing demonstrator.

    I said you’re never going to have a 10,000 lb rocket fly to space, multiple times in a day, built and flown in 18 months like your web site states. You said talk to the marketing department.

    And I told you that our first commercial rocket is likely to be a lot less than 10klb, but that yeah it’s a stretch goal that depends just as much on the financing and market demand as it does on the engineering.

    Regarding my thoughts on your Delivered Isp…Carmack’s comment says it all.

    When you look at our claimed Isp vs the theoretical numbers for our given mixture ratio, chamber pressure, and expansion ratio, our numbers are just as believable as John’s are. If you don’t believe our engine is operating in the low 90%’s, why do you believe that John’s is?

    Towards the end of our discussion I did compliment you on building actual hardware and doing actual testing unlike 80% of the Xcup presenters. I commented how gorgeous your hardware was and that hardware is the only thing that matters and you were way ahead of the curve!

    Thanks. I would add the caveat that flying hardware is all that really matters, and we hope to be there soon.

    Having said that, I do have a prediction….
    There will be no serious competition to Armadillo next year.

    We’ll see. The upgrades we need to make to XA-0.1 to make it capable of competing in the Lunar Lander challenge with a fair deal of margin are not too challenging. It’s the financing that’s more of an issue at this point. If we get any kind of sponsorship at all, we should have a vehicle to field.

    With the amount of building and testing your team is doing, over many many others, Masten Space is certainly a team to watch! You just have to make sure that your Marketing & Press Releases don’t group you with all the other space companies making unbelievable claims!

    True enough. We try to not claim anything that we aren’t pretty darn sure we either have, or can deliver.

    Good talking with you & Keep up the good work!!!!

    Thanks, and sorry if I came off a little offensive.

    ~Jon

  14. Robin says:

    Korey, I’ll bet you a dollar (my limit) that there will be more than two contestants flying in Lunar Lander Challenge next year.

    Jon, Agent K and Agent K-10 aren’t Ansari relatives but they’re still working for the cause. Thanks for showing us around your spaceship — and it was great fun to feel the tarmac vibrating when you fired the rocket engine!

  15. John Carmack says:

    Regarding Isp, I can’t make any specific claims about our engines, because our flowmeters died before we got the high performance injectors working. My estimates are just based on scaling hover times from previous data. I think our 250 psi chamber Isp is somewhat over 200s, but I don’t know for sure. We will probably get back to some test stand work in the coming months.

    Some of my skepticism for a 250s Isp comes from some knowledge about XCOR’s engines, which has bever been officially stated, and I don’t plan on repeating. It would also be better than any of the pump fed alcohol engines listed on astronautix.

    The relation between Isp and mass ratio is worth considering. For our quads, tanks are about 60% of the dry mass when you include the payload, so you would need a 35% improvement in Isp to double the tank mass and feed pressure. For XA0.1, it absolutely makes sense, but it will make less sense as your mass ratio improves. Of course, this is encouraging you to look at pumps, which I think are a bad idea here. As always, I’m looking forward to seeing the results you get with your path.

    Regarding vehicles, our next vehicle will have four engines (5000 lb GLOW), but fixed mounted and relying only on differential throttling. Balancing on a single gimabl has its disadvantages. In this regard, I think Masten has the right idea (I would lose the hinges), but I think they would have been better served building something simpler to get in the air sooner.

    I am going to learn more from the Masten experience as you diverge from the Armadillo path, so I don’t want to argue too strongly…

    John Carmack

  16. David Masten says:

    John and k2unit,

    I think you may be misunderstanding our 250s claim. When we announced it we mentioned this was on our test stand and at least implied that it was our best runs out of a lot of runs. This was a very well controlled test run after lots of tweaking and tuning to determine what our best Isp could be. (and IIRC, the weather was favorable to rocket nozzle performance at the time!)

    On an operational vehicle we expect that we’ll be lucky to get 230 seconds.

    Additionally, we’re taking the overall performance hit on the dry mass side by using a pressurized propellant tank rather than pumps. If we were using the IPA to pressurize itself via a turbopump we’d see lower Isp.

  17. Jon Goff says:

    John,
    Regarding Isp, I can’t make any specific claims about our engines, because our flowmeters died before we got the high performance injectors working.

    Yeah, we accidentally killed a LOX flowmeter early on in development, before we knew better. The big thing is to not let high speed gas flow through them. We haven’t killed one since then (unless we did one in during the long firings at Las Cruces–we’ll see tomorrow or Saturday).

    My estimates are just based on scaling hover times from previous data. I think our 250 psi chamber Isp is somewhat over 200s, but I don’t know for sure. We will probably get back to some test stand work in the coming months.

    Teststand work may not be as glamorous as flying stuff, but it sure helps debug things. I’d be interested to hear how well your higher performance injector does, once you have more solid numbers. Particularly if you decide to do that graphite regen design you guys were talking about. Me, I’m kinda biased toward copper, what with how well it’s been working for us, but would be curious to hear how a graphite one does–I wouldn’t be surprised if you could make something like that work a lot better than the film cooled ones you’ve been using.

    Some of my skepticism for a 250s Isp comes from some knowledge about XCOR’s engines, which has bever been officially stated, and I don’t plan on repeating. It would also be better than any of the pump fed alcohol engines listed on astronautix.

    Yeah, XCOR’s been kinda tight lipped about their engines. I do know they run at a lower chamber pressure (and thus likely lower expansion ratio) than we do–and that probably makes all the difference. As for the astronautix engines, I looked over them and noticed a couple of things:

    1-Most of them used partially watered down alcohol, not technical grade like we do.
    2-Of all the ones that listed chamber pressure, only one had anywhere near as high of chamber pressure as us (and it’s Isp was not surprisingly several seconds higher than our peak number).
    3-All of those were gas-generator turbopumps, which means that the turbopump propellants were probably counting against the engine Isp.

    Most of the ones that did a lot worse than us were running at less than half our chamber pressure.

    It’s important to look at all the potential confounding factors. While our c* efficiency and our Isp as a percentage of theoretical is probably worse than most of those motors on there (we only ended up testing 3 or maybe 4 pintle sets before we hit the one we’ve stuck with), we have more pressure and more expansion ratio, thus it’s not surprising that our actual Isp is higher.

    The relation between Isp and mass ratio is worth considering.

    Yeah, it’s an interesting trade. For the missions that we’d like to do, the slightly higher chamber pressure, higher Isp looks like the right direction for us. If we had started out trying to design a vehicle for the Lunar Lander Challenge, we might have gone for a lower chamber pressure, but since the LLC is at best a step along the way to our real goal markets, the trades came out looking differently.

    But this is the kind of stuff that reasonable people *can* and probably *should* disagree on.

    Of course, this is encouraging you to look at pumps, which I think are a bad idea here. As always, I’m looking forward to seeing the results you get with your path.

    Same here. It’ll be interesting to fly a pump-fed vehicle. I can see benefits for both pressure feds and pump feds, but I think that for our specific interests, we’d either have to go pump fed, or figure out how to make tanks out of maraging steels, and even then the pressures involved are more than a little scary.

    Regarding vehicles, our next vehicle will have four engines (5000 lb GLOW), but fixed mounted and relying only on differential throttling. Balancing on a single gimbal has its disadvantages.

    Once again, it’s a tradeoff. The central engine makes throttle speed a lot less critical. You’re lucky that your first differentially throttled biprop is going to be as big as what you’re looking at. Small vehicles with engines out on long lever arms require higher reaction speed to fly stably. You may end up having to fight with the same issues we’ve been facing.

    Good luck on that though, I could very well be overestimating the difficulty.

    In this regard, I think Masten has the right idea (I would lose the hinges), but I think they would have been better served building something simpler to get in the air sooner.

    Honestly, the gimbals have worked from the start, and faster than expected. Almost all of our trouble has been with dynamic throttling. If I were to change anything, I would actually have gone the opposite direction–slower acting off-the-shelf throttle valves (like those KZCO ones you have) and fast acting hinge actuators.

    I am going to learn more from the Masten experience as you diverge from the Armadillo path, so I don’t want to argue too strongly…

    I understand. Trust me, we also try to learn a lot from you guys. There’s a reason I spent a month last November designing beefier landing gear for instance…

    I think it’s good to have more than one team making a shot at things, because I think you can feel out a lot more of the design space that way.

    Keep up the good work. 🙂

    ~Jon

  18. K2unit says:

    K2unit said…
    Having said that, I do have a prediction….
    There will be no serious competition to Armadillo next year.

    Robin said…
    Korey, I’ll bet you a dollar (my limit) that there will be more than two contestants flying in Lunar Lander Challenge next year.

    Robin,

    Some people call me a pessimist, I prefer practical realist!

    There were about 20 teams that entered the $250,000 FINDS CAT Prize. Many of which said the competition would be won in 6 months. Not a single serious launch attempt! Many years later Ky Michaelson and the Go Fast team did accomplish the goal to space (with a little help from eAc).

    There were about 30 teams that entered the $10,000,000 Xprize. Some of which claimed they were within a few weeks of launching their attempt, to give Rutan a run for the money. Several even said they would continue and fly even if the prize was won. Not a single serious launch attempt since Rutan accomplished the goal to space (with a little help from eAc).

    Now we see about 20 teams that entered the $2,500,000 Lander Prize. Only one of which made a VERY serious attempt this year. Who by the way has a several year running head start and a significant funding resource not to mention a serious team with several experienced members! I’ve heard the same type of response as before from the other teams in this competition…”We’ll be flying next year & We’ll fly even if the prize is won……..If only we could find a sponsor!” Based on my observations and experience, IMHO most teams underestimate; 1) The Challenge 2) The Costs 3) The Build Time 4) The Testing Required!

    To my knowledge there are only two teams signed up for the Rocket Racing League, we’ll see what fly’s next year as well. Painted mock-ups with internal combustion engine exhaust pipes sticking out the side and a fake nozzle don’t count.

    I predicted that there would be no serious competition with Armadillo next year. The key word being “serious” meaning, actually, potentially capable of meeting the 90sec-hover goal. At the current time the XA.01 by their own admission is not capable. It might be made capable, as they are hard working, hands on, hardware guys. MSS is certainly the number two team to watch. As I read, your bet was for more than two …I guess that means three!! Is that three including Armadillo or three others to challenge Armadillo? I’d be really surprised if three teams can jump through the same hoops that Armadillo had to, just to qualify to even make their attempts. So who do you think the third team will be?

    Robin, I’ll take your one-dollar bet! I’ll even up the ante, If MSS makes one successful pass to match what Armadillo did this year, I’ll give one additional dollar to Jon for setting up this bet on his blog! 🙂

    Black Skies!
    K2

  19. Nathan Koren says:

    Of all the people to have their blog turn into a gambling venue, it strikes me that Jon is really one of the less likely… nonetheless, count me in for a dollar, too. I am extremely optimistic that Masten will fly at next year’s challenge, and reasonably hopeful that at least one more competitor besides MSS & Armadillo will be flying as well.

    Although this is indeed a tough hill to climb, one thing to remember is that it’s getting shorter all the time. Armadillo has had perhaps the hardest time of it, because they have really been pioneering much of this from scratch. The LEM and DC-X have done similar kinds of flying before, but not with such off-the-shelf and/or low-cost techniques. So even if they’d had the ability to regularly network with and pick the brains of the LEM and DC-X engineers, much of those projects’ ways of doing things wouldn’t be applicable to Armadillo’s (or MSS’s) way of doing things.

    By so generously sharing the knowledge that they’ve accumulated, I would argue that Armadillo has made this somewhat easier for other teams. Armadillo has learned its share of lessons the hard way; other teams that are paying attention therefore shouldn’t have to. Masten is also being fairly generous in sharing its experiences, so I imagine that Armadillo has & will learn a few things from them as well. It’s one of those “rising tide floats all boats” kind of situations.

    Even if the task is getting easier, I’m not arguing that what they’re doing is *easy*. I would be pleasantly shocked if there are more than 4 competitors at next year’s races. But I would be even more shocked if only Armadillo is flying. The only thing that I can imagine would prevent MSS from competing next year would financial problems — and while those can’t be dismissed, I’m optimistic enough to put my dollar on them flying.

    Not going to be putting odds on the winner, however. Both Armadillo and MSS are great teams, and I expect that it’ll be an *excellent* contest.

  20. Jon Goff says:

    Robin, Nathan,
    Thanks for the vote of confidence. I really would like to see three teams competing this year, because that introduces an element of surprise. So long as all three qualify, it comes down to the tie-breaker flights, and when there’s the possibility of still not walking away with any money at that point, I’m sure it’ll be a fierce competition.

    That said, Nathan’s right. I don’t do or condone the gambling thing. But I don’t censor my comments either.

    ~Jon

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