For those of you visiting my website for the first time, here’s the story so far. I’m Brian Emmett, and in late 2004 I entered a contest setup by Oracle that required me to answer sets of questions on some of their software development tools. The Grand Prize for this contest was a sub-orbital space flight. Yes, a trip into space, complete with astronaut wings. Sometime back in mid-2005, I was contacted by an agent of the sweepstakes and informed that I was the winner of the Grand Prize. Needless to say, I was excited beyond my capacity to adequately describe. The bad news came in early 2006, when I started doing my taxes. Upon realizing that in order to accept the prize I would have to pay over $25,000 to the US government in taxes, I forfeited the prize back to Oracle. The Associated Press contacted me in January of this year about the forfeiture, and an article went out on the wires describing what had happened. The response from across the country and around the Internet was overwhelming. Somewhere amongst all that noise were a man and a company who thought they could help me out – Jim Benson and the Benson Space Company. The idea proffered was simple: bring me on board as a Consumer Test Consultant (read: test passenger). The rest, as they say, is history.
A few weeks ago, I contacted Jim Benson (founder of Benson Space Company and SpaceDev) with an idea. I’ll admit, it started out as a fun, selfish wish, but I thought it was worth a shot. Essentially, I offered to dovetail my love of writing and photography into a series of articles over the next few years, giving interested readers an average guy’s “insider” view of the development progress at BSC. I offered to drop by BSC and SpaceDev every few months and talk to the folks, document the Dream Chaser from computer and wind-tunnel models on through scaled prototypes and eventual flight tests. Much to my surprise and excitement, Jim liked the idea!
So, a few weeks ago I flew down to Poway (a suburb of San Diego) and was able to listen in on the last and final Engineering Trades meeting of the design and analysis phase held between BSC and SpaceDev. The resulting details that follow will, I hope, prove informative and illuminating. Before I dive into the details, I really must admit up front how impressed I was with the whole meeting. The caliber of the engineers involved on both the BSC and SpaceDev teams was evident, and the excitement of all involved was palpable. The consistent focus on customer experience and safety was also very apparent. I’m sure that if any other interested “passengers” had been able to listen in, they would be as convinced as I am of the success of this venture. With that in mind, I hope you enjoy this first (and hopefully not last!) inside look at the design, development and testing of what I hope will be a milestone at the dawning of a new era in private sector space travel.Before we begin, I need to mention a few other disclaimers. These posts will be subject to the approval of Jim and his team, for obvious reasons. I don’t want to be in the position of accidentally divulging sensitive information to potential competitors. Understand that I will only go into as much technical detail as allowed, and I will absolutely not discuss anything deemed confidential and proprietary by BSC, nor will I discuss anything having to do with finances or cost structures.
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On April 26, 2007 I woke up early to head over to San Jose Airport for the first flight down to John Wayne Airport down in Orange County. I was met at the airport by one of BSC’s investors, Greg Autry, who promptly pointed his car south down the I-5 towards San Diego. Somewhere south of Camp Pendleton, realizing we were going to arrive early, we stopped for a coffee and had a chance to talk about what to expect during the day’s meeting, as well as his experiences from the previous Engineering Trades meeting.
First off, what is an Engineering Trades meeting? I tend to think it actually has a couple meanings, both of which I will explain. In the first sense you have the concept of an engineering trade as a set of skills or occupation. Think mechanical engineer, electrical engineer, and so on. In the other sense of the term, and as used in the case of this meeting, “engineering trades” essentially means “trade-offs.”Consider a hypothetical car tire: If you formulate the compounds of the tire to result in a very hard, low friction material you can increase the tread-life of the tire as well as the fuel economy of the car due to a decreased resistance to rolling. However, in formulating a tire recipe in this way, you probably have traded off somewhat in grip and handling performance. Likewise, a tire that you made to have fantastic sticking ability in only warm weather may greatly increase the handling performance of your car, but the tires may only last 15,000 miles and be useless when driving in the snow.
Take this metaphor and now apply it to spacecraft aerodynamics, flight control systems and rocket propulsion systems. This is, I think, a pretty reasonable description of the intent of the meeting; to discuss the variables and trade-offs in designing the Dream Chaser to meet the original specifications and requirements set forth by BSC. (I hope that didn’t come off too pedantic!)In the intervening time between coffee with Greg and the actual Trades meeting, I had a chance to meet Jim, Ken and Hoot. You can read about their professional backgrounds and biographical information at the BensonSpace website. I can honestly say that they were very gracious and welcoming into their (currently) exclusive group of space entrepreneurs and seemed genuinely excited and interested in my participation in their venture. After a brief meet and greet, we all headed over to SpaceDev to join the meeting.
We arrived at SpaceDev some time after noon, and after a brief round of introductions around the table and a quick couple pictures taken of me holding the wind-tunnel model of the HL-20, the meeting kicked off in earnest. Now, I’d be lying if I said I wasn’t just a little intimidated by the level of technical detail that was about to be unleashed, but I must say that in hindsight I was surprised that I was actually able to keep up with most of what was being discussed.
Enough blather. On to the details! I don’t have the actual PowerPoint slide to reference, so it’s entirely possible that the sequencing is out of order, but this is generally what happened.
Aerodynamics
The outer surface of the spacecraft is known as the Outer Mold Line (OML). The OML for Dream Chaser is based on a Russian project started in 1973 named BOR. The intent of BOR was to perform research on the aerodynamic and thermodynamic characteristics of a lifting body space glider. BOR-4 was an unmanned orbiter that was flown several times and made successful orbits, re-entries and recoveries. In 1983, the Vehicle Analysis Branch of NASA began investigating BOR-4 and resulted in the HL-20 project. Small wind-tunnel models were created and demonstrated that the craft had good aerodynamic characteristics throughout the entire flight profile. You can read more details about BOR-4 and HL-20 at the Encyclopedia Astronautica.Lo and behold, SpaceDev had one of the larger HL-20 wind-tunnel models on the desk during the meeting, and boy was it a heavy sucker. My understanding is that a basic model was made, then cast in metal and shaped by hand. This hand shaping apparently explains one tangent of the conversation that discussed the miniscule and negligible variances between the wind-tunnel model and the computer model; I guess the nose was more properly modeled mathematically by a conic and the wind-tunnel model was a little “puffy” in the cheeks.
Some other interesting bits that I took away from this conversation were some of the counter-intuitive control surface inputs that needed to occur in order to steer the vehicle. In the sub to low supersonic range, normal aileron inputs will steer the craft as you would expect; if you want to bank left - push up your left aileron and down your right. In the higher supersonic range, this isn’t the case. Instead, if you want to turn left, you lower your left aileron, which causes the vehicle to side-slip. At this point adverse yaw kicks in and the dihedral effect will bring you around to the left. I can visualize it better than I can explain it. Hoot mentioned that the Shuttle also behaved in this way. The other thing I took away from this portion of the presentation was essentially how stable the vehicle was generally.
Flight Track
One of the main things that Benson Space passengers will get over other potential competitors is a vertical launch from the ground. As this next section of the presentation explained, this created some interesting challenges with respect to G-loading during descent and final turn-in back to the runway. Several different flight profiles and internal seating configurations were discussed, but what I found to be the most important point to take away was how focused and concerned BSC and SpaceDev were on passenger comfort and safety. BSC wants to keep the G-loading as low as possible for optimal comfort.
Flight Control Systems and Control Surface Actuation
So, you’ve got proven hybrid rocket motor propulsion technology providing the thrust. You’ve got the design for a vehicle derived from one that has actually flown into space 4 times, and was tested for nearly 10 years at NASA. You have a general idea of what your flight track will look like from take-off to landing. You know what flight surface inputs are required in order to steer the whole package. How do you actually let the pilot fly the sucker? First, you need a flight control computer, and then you need actuators to actually move the flight surfaces. There are quite a few options for both. For flight control, you can go with no computerized controls, a FPGA (basically a logic chip you can program) or a digital flight computer. Due to the fact that NASA has already created a comprehensive flight simulator for flying the HL-20, using a digital flight computer was an obvious choice given the fact that most of the functions already created could be reused. For the flight surface actuation you basically have mechanical (cable) actuation, hydraulic and electromechanical actuators to choose from. In this case, while the electromechanical are the bleeding edge of the bunch, the hydraulic systems are better understood.
Flight Simulator
As I just mentioned, NASA already has flight simulator software that models the HL-20 flight characteristics. BSC has decided to build a flight simulator to test and train pilots of the Dream Chaser. Hoot mentioned that he has already flown the NASA simulator and has a pretty good understanding of the handling characteristics.
Prototype and Testing
At some point, they actually have to build and test this thing, don’t they? Indeed they do. One of the first things that will happen is the fabrication of a prototype vehicle. Once this whole system is in production and fully functional, a paying customer is going to be strapped into the seat of the Dream Chaser while the vehicle is getting fueled with laughing gas (nitrous oxide, N2O). After the ground crews have topped off the tanks, Dream Chaser, perched atop a first-stage booster, will be pointed upward into the vertical. After that, you’ve got a countdown and then, well you know what happens next!Let’s be clear — we’re not NASA and this isn’t 1960’s. BSC and SpaceDev aren’t doing an “all-up” test like Von Braun and NASA did with Apollo. No, there are several, very important incremental steps that need to be taken before this whole thing goes up. Which brings me back to the prototype. For the first several test flights, the current idea is that Dream Chaser will be launched horizontally from a runway using 4 internal motors with a lower thrust than the final production motors. This accomplishes several things. First, it allows you to test the first booster stage separately. Second, it allows you to test the Dream Chaser in a more controlled environment. As stability and controllability are confirmed, each subsequent flight will push the envelope a little further. First into high subsonic flight. Then supersonic. Then vertical launch without a booster stage. Then a series of “all-up” tests with the booster. As I remember, the current proposed plan is to perform at least 16 flight tests before final production and commercial operations begin.
First Booster Stage
It’s probably worth noting in detail, since I’ve already mentioned it, a little more about the first booster stage. You ARE reading that right. Detailed aerodynamic analyses indicated that the HL-20 Dream Chaser will require a droppable booster stage in order to get you into space, because of the drag created by the rather blunt shape of the HL-20 lifting body. This also means that the motors inside the Dream Chaser itself are air-starts. Once the first booster stage burns out, it gets dropped and recovered by steerable parachute. As that booster stage is falling away, the internal motors ignite and push you to over 3,000 mph so that after motor burnout, you coast those final few miles into space.
I could go on and on and on, but I won’t. There are more details and more exciting steps to take over the next couple of years, so I’ll go ahead and close out this post with a few final thoughts. This was, bar-none, the longest PowerPoint presentation I had ever sat through. Literally almost 5 hours long. If I can draw a comparison, it was sort of like watching Lord of the Rings in the movie theater. You have a sense that a lot of time has passed, but you’re so engrossed and fascinated by what you’re seeing and hearing that you don’t even notice that you’re starving, need to go to the bathroom and have a headache from lack of food. In the end, you’re glad you did it because it was one of those experiences that you don’t pass up.As I said earlier, I am now more than ever convinced that this thing is going to work. The team assembled is top notch, and they really do have the customer focused at the center of it all. Most of all I feel privileged, even as an observer, to be even a small part of this whole endeavor. Man, this is going to be one helluva ride!