Inspired by Michel Van (not Scott Lowther as mentioned earlier) at Secret Projects, who ran into the Gemini inflatable Rogallo wing test videos that are now available (not embeddable so linked only). There are parafoil systems for airdropping stuff, though they don’t seem to be doing flares or line pulls to soften the impact:
And if somebody says parafoils are not maneuverable, I give you a Russian self built RC parafoil:
Speaking of rocketry, a member from the local hybrid group said they have found out the probable cause of roll control problems: the forward fins that were put on the rocket for roll control cause huge vortices when deflected, so that they effect the main fins far aft and the effect might be the opposite from intended.
Minimize delta vee by moving the planets around (this changes the probe's arrival time at the planet). This shows my best solution so far, with some playing one evening, about 13 km/s
This is a nice javascript webpage where a probe is shot from Earth to Jupiter with gravity assists at Venus (twice), Earth and Mars. You try to achieve the lowest propulsive delta vee. You decide when the spacecraft arrives at each encounter and the program basically calculates the rest. It’s quite a nifty little piece of Javascript, the future of web applications is like this. It works fine with Chrome on Linux at least. Probably IE will have problems but who uses that anyway?
I’m ranked at #39 at 12.74 km/s… Far behind the gurus who get below 10 km/s readings! There are apparently some prizes for the top three, but I think people are in it for the fun of it.
From NASA Langley – they did wind tunnel tests on a model. Lots more pictures of various aerospace projects there too, some of them are quite weird. Thanks to Secret Projects forum for the info!
Naturally since Rockwell built the orbiter, this one looks like the orbiter too. With an SSME and RL-10:s (so Rand.org says) and cylindrical tanks, it would have been far lower risk than the Lockheed version that won.
In a sense, the “almost pure rocket” cone, the “flies a little better than a rock” lifting body and the “almost flies like a dangerous plane” winged vehicle are the three main paradigms to reusable vehicles.
Though, with SHARP (or like McD did with active cooling), your lifting body can be sharp edged and have vastly superior L/D compared to blunt ones.
Huh, it always takes a long time to find anything on web pages that are so cluttered up. Here. No idea what the MPGe or miles per gallon equivalent is.
EDIT:
Here’s ERA’s video (they didn’t win, although they were very close. I think they were penalized for driving too fast):
Holy crap. Their vehicle has 1000 Nm torque and does 0 to 100 km/h in 6 seconds.
Well, scaling seems to be my pet issue. I recently wrote something not entirely well reasoned in a comment at Paul Breed’s. (For some reason Chrome complains about blogrolling.com malware there so continue if you’re sure you’re safe.)
So let’s make it better. (A word of caution though, I’m quite sleep deprived now.)
For those who like to jump into conclusions, it’s going to be like this all over again.
Assume a pressure fed rocket first stage has a certain propellant chemistry, tank and thus chamber pressure and must operate in the atmosphere, hence has a certain exit pressure (0.1 MPa or 1 bar or 15 psi is the optimal). Then it has certain thrust per nozzle area.
Now, the rocket needs thrust to lift off. If we assume a constantly scalable shape, its mass will be base area times length times density.
Since the maximum fittable nozzle exit plane also depends on the base area, we find that for a certain area, the rocket can only have so much mass – or that the rocket has a maximum density times length parameter. If we assume the propellants have been picked early on, density is set and the rocket only has a height constraint. Each pressure and propellant chemistry basically has a “characteristic length” that can’t be exceeded. Otherwise it can’t lift off.
The higher the exhaust velocity, the smaller the nozzle, so raising chamber pressure reduces the needed nozzle size per thrust and the rocket can be lengthened.
For small rockets, I’d hunch that they have little length and thus they don’t really have to worry about this. They can be as thin (and thus long) as practical, to try to avoid drag losses.
For upper stages, the thrust to weight needed is less and the weight even less so it’s even less of a problem – except that the expansion ratios can be huge since there’s no back pressure anymore. Still, with small rockets, pretty huge expansions might be possible without having much problems because the second stage is very small (=also short) anyway and thus there’s little mass per nozzle exit plane area.
On really tall rockets like Saturn V, the thrust per base area has to be huge, hence it had to have those base extensions for the corner engines (note how the N-1 had a conical shape with a wider base, the engines had a bit higher pressure but the upper stages were kerosene – these cancel out a bit but the base of the rocket had some empty space) . Similarly with STS, putting so much thurst on the tiny orbiter’s tail required high chamber pressures and some tail shaping
I don’t have any numbers handy, but if we assume a 10 m tall 1000 kg/m^3 density (water) rocket, then it has 10,000 kg per m^2 or the thrust required for a 20 m/s² acceleration is 200,000 N/m^2. This is easily achievable. With an exhaust velocity of 2000 m/s, the mass flow needs to be 100 kg/(s*m²) to produce that thrust. Again with the exhaust velocity that mass flow means a density of 0.05 kg/m^3. Air’s density is 1.2 kg/m^3 at 300 K, so that’s 20 times less dense which means hotter, the density is like hot air at 6000 K. Though the molecules might be mostly lighter OH instead of N2 and O2, making that rocket exhaust at 3000 K for the density. Rocket exhaust isn’t that hot – it’s cooler and denser and thus more thrust per unit area.
For a second stage we can look at the pressure fed AJ-10 from Delta 2: 1.7 meters diameter (certainly constrained), 40 kN of thrust. For a T/W of 1, density of 1000 kg/m^3, we get 4 tonnes and 1.7 meters of depth. Quite a stubby stage with a roughly spherical tank! Isp is 321 s. The real Delta II second stage weighs 7 tons and the payload is some too, but reusable rockets won’t have such high performance first stages (nevermind solids!), so they might need more T/W.
Oh, BTW, I assume three stages to orbit for pressure feds though I haven’t looked it that closely. Mass ratios and ISP:s I’ve only hunched.
Rand Simberg talks about impedance matching. So I’d like to make a post of my comment there (I’ve always wondered why this obvious alternative gets mentioned so little…)
What to do when you arrive at Mars or Earth with your solar electric propelled vessel?
So, the problem with most low fuel demand velocity change schemes is that they only give slow accelerations. Low fuel high velocity change means solar or nuclear electric propulsion and aerocapture mainly.
High delta vee aerobraking is hard to do in one pass – it gets dangerous because of atmospheric variability and potentially other reasons.
Simple: detach a small capsule with the humans that goes directly to the surface (with only days of life support) and leave the untended craft to do multi-pass aerobraking. Hitting van Allen belts a few more times or taking a long time doesn’t matter that much with no humans onboard.
You could also potentially ultimately leave the long distance craft at some Lagrange point instead of LEO. (Cue some clever and complex maneuvers to save fuel – maneuvers that take long.)
Something similar could also be done when a long distance stack is assembled in LEO: send the humans there only after it’s through the belts. They can go with a smallish capsule again. Potentially at some Lagrange point, or in space without any fixed reference, just along the way. It could be dangerous though if the capsule doesn’t have much life support.
Many of these things have potential delta vee penalties as well as timing inflexibilities, but they could have enough other benefits that they should be considered.
All these people had to get paid. Even when there wasn’t a launch. Well, to be exact: until the money was spent and there weren’t gonna be any more launches, which was a few years from this photo.
It doesn’t have the same sound as “The Last V-8” now does it? When you look at what’s happening in the world of automobiles, you get some idea of a change. It is always slow, yet I predict that when it happens, probably starting before the end of this year, people are taken by surprise.
Why Would Anyone Buy A Hybrid Car?
It doesn’t have that much better fuel economy than a modern petrol or diesel engine if you drive out of the city, and it costs some more and is complicated. New turbocharged and variable valve engines can do pretty well because they can be built to opearate in a flexible manner. BMW has even introduced a technique that could be called a “virtual hybrid” – where the aircon compressor and battery charger are disconnected when the gas pedal is pushed to the bottom, resulting in extra power available for traction – allowing a smaller engine to achieve the same acceleration.
In some cases, like buses that need to stop often, hybrids make great sense, but otherwise I see the improvements in ordinary direct internal combustion engine driven cars narrowing the gap quite considerably. On the highway the hybrid has no advantage.
A Seemingly Small Addition
Volvo V70 Plugin Hybrid Prototype
So, add a grid recharge capability and you have a plugin hybrid. By itself that’s not much yet though, you have to enlarge the batteries too. Since most trips for most people are commuting and errands, they’re short and can be done entirely on battery power. You also still haul the gasoline engine along and it is used on longer trips. Most problems solved right here? Sounds easy.
The problem is, gasoline is very very energy intensive. If a car uses 8 L for 100 km and a 10 kWh worth of energy, then tankage of 40 liters gives about 50 kWh of energy. Done in 50 seconds this stream of gasoline through the hose is worth 1 kWh per second or 3.6 megawatts. High enough temperature superconductors have not yet been invented that would make a hand-attachable 3.6 megawatt car charger possible. If we generously assume 240 Volts and 40 Amperes, the charging power is only 10 kilowatts. The largest home appliances like sauna stoves and water heaters are in the single kilowatts range. They often use 380 V three phase power here, but that gets slightly impractical for a car charger. This thousandfold disparity in energy replenishment speed is striking. An optimistic 10 kW charger would charge a 100 km drive’s worth of energy in an hour. Certainly useful for commuters. Charging as range extension seems doubtful. Our summer cottage is 300 km from Helsinki. If a full battery only lasts the first 200 km, one would have to stop at a loading station for one hour before one could drive the rest of the way. Not realistic. The penalty of lugging around the heavy and complicated IC engine has to be bitten at this point of battery development.
Battery Improvements?
There exist some pretty high energy per mass battery technologies right now, but they are expensive and use rare materials like cobalt that they can never really be mainstream solutions on something that stores energy in the megawatt hour class. Hopefully with enough money now available, some cheaper and less material intensive ways to store electrical energy can be developed.
Your Local Correspondent
Naturally, Finland would be a pretty ideal place to have electric and plugin hybrid vehicles. A significant portion of the populace keeps their cars parked in a spot with an electric socket nearby – those house timers that turn on the cylinder block heater on an hour or so before leaving for work in the wintertime, meaning less fuel use and wear for the engine. It is trivial to use those 240 V outlets for electric car charging. Also, electric cars are actually manufactured in the city of Uusikaupunki, Finland by Valmet. The Th!nk City is one. Too bad because of insane tax policies, it is not actually sold here – at the moment you can only get them in Norway, Austria and Holland. The Fisker Karma electric sports car will also be manufactured in “Uki”. I think they have a long nose on the car for Freudian reasons – since it doesn’t need to hold a long block internal combustion engine – or maybe it’s just that buyers are conservative. And then there’s the e-cars now project aiming to refit old Toyota Corollas with electric motors and batteries. But there’s more.
Automotive X-Prize
There’s that going on, which is actually interesting! My favorite vehicle is the Peraves E-Tracer.
Here are the results from August 2 but I still don’t know what will change / what is coming because the pages are unclear: [EDIT: fresh info at the blog indicates some testing is still going on]
1st Place Team Lithium Ion Motors of North Carolina (125 MPGe average fuel economy for the event) 2nd Place RaceAbout Association of Finland (0.179 seconds behind the leader and 100 MPGe average fuel economy for the event) 3rd Place TW4XP of Germany (11 minutes, 36.9 seconds behind the leader and 139 MPGe average fuel economy for the event) 4th Place ZAP of California (DNF – 48 laps completed) 5th Place Aptera of California (DNF – 18 laps completed)
The Raceabout team is from Helsinki’s Metropolia university of applied sciences. They have a long background of building electric vehicles, and it’s nice to see something in the competition that looks like an actual car, yet still manages to do so well.
RaceAbout's E-RA vehicle in the Automotive X-Prize 2010 competition
Hopefully the politicians here can get something sensible done, and the super-high taxes on electric vehicles (basically, anything that isn’t gasoline or diesel is considered fishy and is taxed hugely) can be dropped so we can start seeing more of them here! The current situation is a travesty!
The Batillus class supertankers built in the seventies that had a larger mass (gross tonnage) than anything now were scrapped pretty soon after since they had to sit around for lack of work. The oil crisis hit at a bad time, and it probably costs quite a lot to keep such a large ship in sailing shape. They probably were not very practical either. Out of the ten longest ship classes on list at Wikipedia, most have been scrapped already. The environment is hard. The Jahre Viking / Knock Nevis tanker that was the longest ship in the world was scrapped only recently, having been built about the same time as The Batillus class.
Gravity Loss (now moved to gravityloss.com) 
