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    New Hiring, New Engine, and XA-0.1 Replacement Plans

    jongoff on 1/4/2008 at 5:54 pm — General —

    It’s the beginning of a new year, and there are many changes afoot at MSS, so I figured it was about time for a bit of an update. A lot of people were curious about what direction we would end up taking after we damaged our vehicle last month, so I wanted to discuss some of our plans for this year.

    MSS Now Hiring
    One of the biggest changes that we’re undergoing at the moment is an effort to augment the core team here at MSS. We haven’t had any real changes to our core team since early 2005, but situations change over time, and we’ve been recognizing the need to expand and diversify our skillset as a team. Basically, we came to the conclusion early last year that there are a couple of areas that we really need to have someone in-house with solid expertise in, particularly Guidance, Navigation and Control. We’ve updated our careers page with more details, but I’d like to go into some of the reasoning for why we’re looking to fill some of these positions.

    GN&C Engineer(This position has been filled)

    Even though we’ve been working with outside groups to provide us with expertise in this area, we’ve long since come to the conclusion that having someone in-house who has a good understanding of controls engineering is very important. Having someone with real experience in that area is critical to properly specifying and designing actuators and other subsystems. A lot of the control systems related challenges we’ve had to fight through over the past year and a half came from not knowing what to expect, “failure to overcommunicate” when it came to specifications, and just the general learning curve of figuring out what data was important and how to actually verify that things were performing the way you expect them to. Quite frankly, the basic rocket propulsion part of our vehicle has been the easy part. Now, we’ve actually learned a lot of these things by now (the hard way), but we’d like to have someone on board who can work with us when we sit down to do a new vehicle, and make some models to predict the kind of specifications we’ll need for throttle valves, gimbal response etc. We’d also like to be able to have someone on board who knows what they’re doing controls-wise so we can make modifications to our flight code as we do flight testing, to speed up the iteration cycle. GN&C really ends up being the heart and soul of a VTVL rocket system, and not having anyone in-house who even “speaks the language” is a situation we’d like to change. If anyone reading this happens to either have experience in Multiple Input, Multiple Output control systems (particularly in an aerospace or aviation environment), or to know someone who does, they can find more information about the specifics of what we’re looking for here.

    Senior Engineer/Project Manager
    Several months back, we had a good friend (and competitor) of ours drop by for a visit while he was in the area. One of the things he brought up got me thinking a lot about the various approaches there are to building an engineering team. Our friend’s company pretty much only hires people with 10+ years worth of experience in aerospace engineering. His philosophy was that sure you have to pay them a lot more, but you’re getting a solid engineer, a known quantity, someone you can depend on. There’s some truth to his philosophy, and his company has been making good progress. On the other side of the spectrum, we have some other friends whose company doesn’t have a single person who had previously done professional rocketry. I’m not even sure if a single one of them had ever fired a liquid rocket before they started their company. But they’ve also been very successful over the years, and have earned a good reputation in the industry. We’re probably a lot closer to the latter than the former. I’m not sure of this, but as far as the entrepreneurial space launch community goes, we may have the youngest engineering team overall. Dave’s the only one who works here full-time that’s older than 30. I’m the only one who ever worked for an aerospace company before this job (and that was just as a contract proposal writer/patent writer), though Pierce and Dave had both built and flown peroxide monopropellant amateur rockets.

    All told, both ends of the spectrum have drawbacks as well as benefits. The more I’ve thought about this, the more I’ve come to the conclusion that like many things in life, the best option is probably somewhere between the two extremes. I had a chance recently to meet some of the members of the propulsion team for another major alt.space company, and I think they do a really good job of this. While they have some very experienced industry veterans heading up the department, the younger engineers outnumber them about 3 to 1. The younger engineers get a great mentoring environment, while adding a lot of enthusiasm, new ideas and approaches, and excitement to the mix. Having at least some experienced engineers on board also helps make it so the younger engineers don’t have to learn all of their lessons the hard way. Before I had met that propulsion team, I had already been leaning towards the belief that the best way to organize an engineering group is to have a balance of some more experienced engineers along with a larger number of younger engineers, but now I’m pretty much convinced.

    Especially since we’re now starting into some more complicated projects for some of our customers, we’ve decided that as part of the restructuring of our team, we’d like to bring on a Senior Engineer/Project Manager. Someone who’s been in industry a bit longer (though not necessarily the launch vehicle industry–there are several other hardware related industries that would also provide useful experience), who may have a broader depth of knowledge, and who has more experience with managing complex projects than any of us do. You can find more details about the specifics we’re looking for here.

    Office Manager/Accountant
    On the business operations side of things, we’ve decided to bring on an office manager to take some of the weight off of Dave, so he can focus more on the engineering side of things. Trying to be the President, CEO, “Speaker to Regulators”, Accountant, Office Manager, Ground Controls Programmer, Pilot, Network Engineer and Janitor all at the same time is a little bit more than you should leave on any one person’s plate for too long. More details on that position can be found here.

    Technician/Fabricator
    The last position we’re currently looking to fill is for a technician/fabricator. Ian’s been doing a lot of our fabrication work, but we’d like to bring on some additional help whose sole focus is this area. Basically we’re looking for someone with an attention to detail and who has good shop skills and the willingness to learn new skills and techniques. Prior experience in a machine shop, or as a welder/fabricator, an auto or airplane mechanic, or other related technical backgrounds is strongly desired. More details here.

    Technical Plans: XVT-750LIT-1 and XA-0.2

    On the technical side, we thought long and hard after XA-0.1 was damaged last month. Our first inclination was to just patch her back up and get her back in action. It would’ve only taken 1-2 weeks to get back into shape, but the more we thought of it, the more we agreed that it was time to move on. One of the issues that has been plaguing us with XA-0.1 for over a year was that due to a “failure to overcommunicate” we selected a throttle valve concept and hinge actuation system that didn’t have adequate response characteristics for controlling a multi-engine vehicle like ours. The response characteristics would’ve been adequate for a single engine vehicle like some of the ones Armadillo has made, but that would’ve required redesigning both the engine and the vehicle as a whole (and would led away from our long-term path), so we tried to just see if we could make the system work in spite of the actuators. However, after this last flight, we realized we had finally reached a point where it no longer made sense to keep trying to force XA-0.1 to work, and that instead it would be better to take all of the lessons learned and move on to a new vehicle.

    XA-0.2
    For the new vehicle we narrowed down the options to three main alternative approaches:

    1. Build a subscale vehicle using smaller engines with much faster actuators and a more symmetrical vehicle arrangement with an inline tank configuration.
    2. Build another XA-0.1 scale vehicle, but with some improvements such as an inline tank configuration, engines closer to the centerline, wider baseline landing gear, and much faster throttle and gimbal response.
    3. Finish XA-0.2 but with upgraded engines, throttle valves, and hinge actuators.

    We decided to go with the third option for several reasons. First off, bigger vehicles that are more symmetrical are easier to control than smaller vehicles. The much higher inertial matrices make the vehicle less sensitive to perturbations, which greatly relaxes the requirements for response time on the valves and gimbals. The fact that XA-0.2 has the engines closer to the inside, and the landing gear further out doesn’t hurt either. Second, we had already built a lot of the hardware for XA-0.2 by the time we stopped work due to the tanks problem, and we had already put the design through an external design review, so we had at least some validation from an experienced team, that our concept and approach was on the right track. Third, we have a customer that wants to use XA-0.2 this year, and if we built another vehicle first, we might not be able to deliver in time. Fourth, XA-0.2 was the only option that actually moves us forward towards our eventual goal of fielding XA-1.0.

    There are a couple of changes in the works already for XA-0.2 compared to the original design we were building for the X-Prize Cup. First off, we’re going with a centralized engine computer for this vehicle. We realized that with the vehicle we had, we had lots of computers, but no real redundancy. If any of the engine computers (or the vehicle computers) had died, we would’ve lost the vehicle anyway. We’ll still probably have valve and hinge control boards as well as a sensor muxer board down on the individual engine modules, but all the main smarts will be run off of the same PC-104 stack that runs the vehicle Onboard Flight Management System (that controls the shutoff valves, vent valves, ground ops, and range safety). The other big change is that we’re going to rework the entire engine design.

    XVT-750LIT

    One of the quirks of the original XA-0.2 design was that since we were using the original 500lbf engines, the vehicle would only have enough thrust to take off with a half-load of propellant. That would’ve still given us about 120-150s worth of flight time, but in order to get enough thrust to take off with a full propellant load we were going to need either a fifth engine, or to upthrust all of the engines (what we were then calling XA-0.2B). Since we were going to need to redesign the valves and actuators anyway, and since there were still one or two remaining squawks with the engine design that we wanted to fix, we decided that now would be a good time to upthrust the engine, and roll in all the lessons learned from our previous engines.

    We’re in the process of releasing the prototype for production. Our performance goals are to achieve a 50% increase in thrust compared to our previous engines (ie 750lbf) at a much lower chamber pressure (250psi vs. 550psi), all without increasing the weight by more than 50%. We’ll take a slight Isp hit due to the lower pressure, but it will also make our tanks a lot easier. In fact, it brings our tanks down to a similar pressure range to what have been done by Armadillo and Paragon. And this time around we’re optimizing the expansion ratio for lower altitude flights, since our near-term projects are mostly low-altitude missions. What this means is that in spite of having a lower peak Isp, if we hit our targets we should still have almost as good of a mission-averaged Isp for long hovering missions (such as the Lunar Lander Challenge). The engine design also features a more compact igniter style, a new chamber/igniter interface, and at least as of this moment is only predicted to weigh less than a pound more than our existing engines. The design is a scaled version of our previous engine, so we have pretty high expectations of it working well for us. Here’s what the engine looks like (minus external plumbing):

    XVT-750LIT-1 CAD Model

    We need to get the trailer rehabilitated before we can start testing, but we’ll probably be doing that while this new design is out for machining. We’ll post more details as we have them.

    Contracts and Other News

    We recently finished sending off the final report for our first commercial contract, which involved doing a design review on a 6-axis Solid Rocket Test Stand designed and built by the Florida Institute of Technology (in conjunction with Space Florida). This stand is to allow students and other groups to test solid motors up to 10klbf, with a really good DAQ system. We’re talking forces and torques at high enough resolution to measure any sort of combustion instability issue you could think of. We look forward to working with these guys again in the future.

    FIT 6-Axis Test Stand

    We also have another major project and some licensing agreements in the works that we can hopefully say more about in the near future.