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John Carmack's Test Liftoff a Success
brainstyle writes "Space.com is reporting that John Carmack of Armadillo Aerospace (and who apparently has some game design hobby) has had a successful launch of the prototype of its entry in the X-Prize. From the article: 'I had tried several algorithms on the simulator before settling on this one, and it behaved exactly the same in reality, which is always a pleasant surprise.'"
If we can't shoot it or drive it, what good is it ?
he'll have a deadline more precise than "when it's done" if he wants to win the X-Prize.
'I had tried several algorithms on the simulator before settling on this one, and it behaved exactly the same in reality, which is always a pleasant surprise.'
I know not this reality which you speak of.
i almost thought you knew what you were talking about, until you got to the Van Halen belt.
With TONS of bugs and frogs, and a nonsensical japanese name
I think you're thinking of John Romero - I hear he's working on a rocket powered by nothing but his own over-inflated ego.
Id versus ego, who will win? Mwuhahaha!
Ahem.
Tedious Bloggy Stuff - hooray?
For those of you that are underwhelmed by the 310 pound vehicle, do note that the big vehicle (1500 lbs) that can actually carry people is also flying. Look back in the Armadillo updates around April 19 for testing video. We have since reworked the propulsion system to follow what has worked so well on the subscale vehicle, and should be testing it this weekend. If it works well, we will be repeating the boosted hop with the big vehicle next week.
The flight time is currently limited by federal law to 15 seconds of rocket burn time. We have a waiver coming to extend that to 120 seconds, but beyond that we will need a full launch license.
The significance of all this is that the vehicles are intended to fly up, come back down and land right where they took off from, all without ablating, expending, or seperating anything. It should be possible to have turn around times under one hour even for quite large vehicles.
BTW, Doom beta testing is going very well.
John Carmack
You're trolling, of course, but it's a good troll because it exploits a gap in knowledge most people arguing this issue aren't even aware of.
Without taking time to go into a long reply with many examples, suffice it to say that the Framers knew very well the difference between "arms" and "artillery." They specified "arms." Typical military rifles (a flintlock back in the day, an assault rifle today) are fine. Military weapons of serious, if not mass, destruction (a cannon back in the day, a nuke today) are not fine.
There can be some reasonable disagreement about where, exactly, to draw the line. In the old days, all artillery required horses to drag it and a crew to serve it. Nowadays, an RPG is a one-person weapon. Thus, the old criteria of "man-portability" may no longer be relied on to draw a bright line between arms and artillery. Where the line is to be drawn is a fine thing for politicians to debate into the wee hours, but it doesn't inform this discussion. FWIW, I think we do a very good job of drawing that line, today. Automatic weapons are very heavily regulated and taxed and the owners are seriously investigated before being given permission to acquire them. Less militarily-capable weapons get less regulation. More capable weapons draw more scrutiny. (Hell, if you want it and can afford it, you can, as a private citizen, own, operate, and shoot out of a fully-operational fighter plane with multiple functional machine guns. But you'd better be rich and have plenty of time and patience to jump through all the bureaucratic hoops.)
In summary, then:
There's a right to bear arms.
There's no right to bear artillery.
Simple, huh?
preface: This is a joke
John Carmack always gets +5 when he posts something. It's not even a question, moderators are drawn to give up those points like a heroin addict looking to shoot up when they see his name.
I think one day JC is going to just put "I farted, it stanks" and hit OK by accident, and then see the following on the comment:
+1 Insightful
+1 Funny
+1 Interesting
+1 Informative
A variety of responses:
We don't expect to win the X-Prize, both because Burt probably has it in the bag, and we are behind schedule. We still plan on continuing our development, because our designs are nearly an order of magnitude cheaper to fabricate and operate than Space Ship One, and orders of magnitude matter. If SS1 crashes on Monday, we will throw more time and resources at an attempt, because there really is no other contender, but it will be a long shot.
We could have flown an unguided rocket to very high altitudes a long time ago, but we have instead concentrated on control systems, which is where the important work needs to be done. A team that was busy flying rockets to hundreds of thousands of feet altitude, then decided to add a guidance and control system to their rockets would be in for many rude surprises at high energy levels.
This isn't immediately obvious, but an X-Prize class vehicle pretty much requires an active control system (a trained pilot with appropriate controls is also an active control system). A short burn time rocket, like the recent CSXT 100 km shot, can live with just aerodynamic stabilization (note that it also landed 20 miles away), but the G forces are far too high for people. As the burn time lengthens with lower acceleration forces, the vehicle will gravity turn away from vertical, making it almost impossible to keep a 60 second burn time even accelerating upwards.
People that harp on about propellant specific impulse in the context of suborbital rockets are like programmers that obsessively optimize a function that isn't a hot spot. The goal of a rocket ship is not to deliver specific impulse, it is to move a payload reliably and cost effectively. Isp can always be traded away for mass fraction, and quite often you can improve operability or reliability by doing so. With our new vehicle designs using a single engine and jet vanes instead of four differentially throttled engines we are more likely to consider trading some engine and system complexity for performance, but issues like the requirement for deep throttling still make it a complex decision.
I do Armadillo work on Tuesdays, weekends, and late at night. At Id lately I have been working on next-generation rendering technology while the rest of the company manages the Doom beta process.
I don't issue press releases. I just publicly write about what I am working on, and other people find it noteworthy enough to talk about. All of our development work, including the dead ends and mistakes, is fairly well documented on the Armadillo Aerospace website.
John Carmack
> I figure you need about four times as much fuel at liftoff for a vertical rocket-borne landing as you would for a parachute- or wing-borne landing.
No, not even remotely close.
You only need enough propellant to kill the terminal velocity of the vehicle to land it safely. A vehicle that is stable reentering base first has a Cd right around 1.0, and any high performance rocket vehicle is going to be coming in pretty light after it has burned most of the propellant. The V2 impacted the ground still supersonic because it was aerodynamically stable nose first, so it maintained its 0.15 or so Cd on descent. A reasonably stubby base first reentry will have a terminal velocity of only 200 mph or so.
Killing that speed with a comfortable safety margin takes about 400 pounds of propellant in our vehicle, compared to 8000 pounds of propellant burned on ascent. A higher performance rocket engine could do it with propotionately smaller amounts. A parachute / drogue / ejection system for this weight vehicle is indeed lighter, coming in at about 100 pounds, but that brings a number of disadvantages with it, like coming down tens of miles away and still needing final impact attenuation.
We wanted to use parachtues as a quick hack for the X-Prize, but the test range where we were planning to fly was going to require a half million dollars of "engineering support" and wanted us to carry a thrust termination system (bomb) on the vehicle to satisfy themselves that it won't drift out of the range.
Long term, there is no question in our minds that powered landing is the way to go. We just were given a pretty strong incentive to go there earlier than we were planning.
John Carmack
Actually, you underestimated this one.
Since the "payload" of an X-Prize vehicle is three x 200 lb people, needing 400 pounds of landing propellant turns our 850 gallon tank vehicle from a three person vehicle into a one person vehicle.
In the most negative light, you could say that powered landing (with a low performance propellant like we use) takes away two thirds of our payload capacity, but that is a poor metric to base decisions off of, because operational issues have historically been orders of magnitude more important to cost effectiveness than propellant consumption.
We can get the 400 pounds back by either going to a carbon fiber tank instead of a fiberglass tank (cost: $40k up front design fee, then $25k per tank, compared to $9k for the fiberglass tank), or by upsizing everything to a 1600 gallon fiberglass tank (cost: $17k for the tank plus more for bigger engine plumbing, catalysts, and nozzles).
Upsizing the tank is lower risk, because it only uses suppliers that we already buy from, while the carbon fiber tank job would be custom from ATK, and I have already had two other vendors back out on me for big tank work. We already have a 1600 gallon fiberglass tank on hand.
Our mixed monoprop has a measured sea level Isp of 145, with normal increases with altitude. Our big vehicles have a mass ratio of about five, takes off with somewhat under one positive G of acceleration, and has a somewhat regressive thrust profile from partial blowdown pressurization. That combination is sufficient for suborbital flights. A 200+ Isp biprop can do it with a mass ratio of three, but the vehicle gets a lot more complicated to build and operate.
John Carmack