This is exciting, because it opens the door for space elevators that don't rendezvous with a stationary point on the ground, but with hypersonic planes.
This puts the tensile strength necessary into the realm of existing high-strength polymer cables.
If we could build a robust fully-reusable space plane that can go Mach 15, and we could also find a way to rendezvous it with a rotating tether, we could free ourselves from the nastiness of the rocket equation and achieve inexpensive space access.
>If we could build a robust fully-reusable space plane that can go Mach 15, and we could also find a way to rendezvous it with a rotating tether, we could free ourselves from the nastiness of the rocket equation and achieve inexpensive space access.
If we could build a robust fully-reusable space plane that can go Mach 15 free from the nastiness of the rocket equation then we already practically achieved inexpensive space access :). If you look at the rocket equation - it is the first 15 Mach that require to burn almost all this mass of fuel through all these big engines pumped from all these big tanks. Once you're going 15 Mach - to get to the 30 Mach for the payload of N kg, you'd need to burn only ~N kg of LH2+LOX (4.5km/s nozzle speed) - so not much gain would come by replacing rocket propulsion with anything else on the second half of the acceleration. The first half is the problem.
If we could build a robust fully-reusable space plane that can go Mach 15 free from the nastiness of the rocket equation then we already practically achieved inexpensive space access :). If you look at the rocket equation - it is the first 15 Mach that require to burn almost all this mass of fuel through all these big engines pumped from all these big tanks.
By not requiring full orbital velocity, we are freeing ourselves from the particular nastiness of the rocket equation on the surface of our planet. Our gravity well is just deep enough, that SSTO is just beyond the edge of what we can achieve with chemical rockets. I proposed Mach 15 because it's significantly less than the Mach 20 result, but in this case it's clear that I still chose a number too high.
The problem with rockets is the 0 part of H20. 0 = 15.9994, H = 1.00794 so by burning oxygen from the air you drop 15.9994/ (1.00794 * 2 + 15.9994) = 88.8% of the weight of your fuel which makes everything a lot simpler. Less weight takes less fuel to lift which reduces the size of the craft which saves even more fuel or let's you build a stronger craft or one better suited for reentry.
An air breathing craft that can get to Mach 10+ would easily drop the cost of getting to space to 1/10th what it is today and let do things like have some reserve fuel in case you messed up the landing and want to come around for another pass. If you can hit Mach 20 then LEO starts to take less energy than flying around the world.
>The problem with rockets is the 0 part of H20. 0 = 15.9994, H = 1.00794 so by burning oxygen from the air you drop 15.9994/ (1.00794 * 2 + 15.9994) = 88.8% of the weight of your fuel which makes everything a lot simpler.
there are 2 issues with oxygen from the air:
1. the air is moving fast relatively to the aircraft frame of reference. To burn it, the air should be slowed down in the aircraft frame of reference. That means acceleration of that air in the Earth frame of reference. It isn't a noticeable energy loss below Mach 2, yet above the Mach 2-3 it starts to impact the efficiency of the air breathing scheme to the point that rocket engine carrying oxygen with it (ie. accelerating it in the Earth frame of reference and keeping it non-moving in the aircraft frame of reference) doesn't look that less efficient, and the higher the speed the less the efficiency gap. Scramjets (no slowing down of the air) while seemingly fixing that problem face the other side of the same issue - trying to impact even small amount of additional momentum on the already fast moving air (in the aircraft frame of reference) requires an unproportionally increasing (the same v square) amount of power.
2. due to composition of the Earth atmosphere, to burn 1kg of oxygen, the aircraft need to pump through engine - ie. accelerate as described in the point 1. above to the speed close to its own in the Earth's frame of reference - 5 kg of air.
The jet propulsion itself doesn't care that mass m being thrown out of the nozzle with velocity v consists of - H, O2, H2O, steel balls or foam - doesn't make difference as long as it is of mass "m", and the aircraft needs to come up with that mass somehow - carry it with itself or gather from outside (and accelerate the mass or try to impact momentum on the already fast moving mass).
Take the points above, add the simplicity and low weight of the rocket engine in comparison with air breathing engines and you will see why rocket engines are dominating the arena.
1. Scramjet's don't suffer all that much from having extra air move though the engine because they don't slow that air down.
2. Scramjet's have already been demonstrated at over Mach 9.5 and are still more efficient than rockets at those speeds. (aka more thrust per unit fuel.)
3. Scramjet's are actually fairly simple designs compared to a traditional get engines. (Modeling and testing them however is much harder.)
Granted, there are plenty of downsides which is why we have not built anything like that. But, the issues are far more in line with heat dissipation and drag vs. limits on the basic physics. Still the main limitation seems to be the far lower thrust-to-weight ratio.
>...vs. limits on the basic physics. Still the main limitation seems to be the far lower thrust-to-weight ratio.
that exactly the basic physics limit of the scramjet that i was talking about :
"the other side of the same issue - trying to impact even small amount of additional momentum on the already fast moving air"
From my brief read and perhaps faulty understanding. This is a rocket with a more planes aloes reentry vehicle. It only goes Mach 20 cause it's falling from space.
One obvious example is manufacturing in zero g. parts can be thrown from operation to operation, rather than having to trundle along on a conveyor. launch would have to get pretty damn cheap to make assembling cars in space worthwile
A better example might be fancy chemicals. Rather than purchasing a "very expensive machine" to ensure a specific environment for reaction, it might be cheaper to send the materials to zero g for processing. I'm not a chemist, but watching astronauts play with bubbles and flames in space makes me think you could get a lot of precision by modeling everything as perfect spheres. So, the reactions are simper to model, easier to get accurate and precise outcomes.
It's wish fulfillment for sci-fi geeks, a deus ex machine made out of unobtanium which purports to answer the question "Is there any reason to go to space other than fulfilling the fantasies of sic-fi geeks given that getting to space is so fantastically expensive as to swamp all benefit of commercial activity other than artificial communications satellites?"
It's not quite that expensive -- NASA's budget from 1958 to 2011 was about $800 billion. To put it into perspective, the US has a yearly military budget of about $660 billion.
The most significant difference between this prototype and existing ICBM technology is that the reentry vehicle has more lift and less drag.
It's counterintuitive, but re-entry vehicles are typically bluntly shaped because it reduces the heat load on the nose cone by pushing the bow shock further out in front of the craft. The downside of this is higher drag and less lift, so ICBM warheads fall more than they glide.
True, but there are things we could call ballistic that are low drag (they also are likely low lift). A typical pointy artillery shell being a great example.
>The HTV-2 is part of an advanced weapons program called Conventional Prompt Global Strike, which is working to develop systems to reach an enemy target anywhere in the world within one hour.
Wait, but don't ICBMs have like 40 min strike time for any target in the world since, like, sixties? (Ok, in the sixties they couldn't aim this fast).
Yes, but launching an ICBM has the rather unfortunately consequence of telegraphing the message that you are about to nuke someone. Hence the program is a non-ballistic one that seeks an alternative means of delivering a payload as quickly. As a bonus, I gather that the HTV program promises to be more accurate.
It seems like that sinks the entire idea. A weapon that is suitable for a nuclear first strike doesn't seem like a weapon that is suitable for much else, unless we're on unimaginably good terms with all the other nuclear powers. The fact that we must consider the possibility of military conflict with China makes it especially troubling to consider building a weapon like that and developing a defense strategy that depends on it. Can you imagine getting in a war with China and suddenly launching a dozen ICBMs with conventional weapons on them? Of course we would never do that. It would be insane to do anything that looked like a first strike during a conflict with China. Or Russia, for that matter. Hell, it would probably be insane to do it even if we weren't at war with Russia or China. The mere fact that this plane could deliver a nuclear weapon to Moscow or Beijing in under an hour means that it would be unwise to use it for anything else.
The whole point of a weapon system like this is to develop the capability to project sufficient force to anywhere it's needed. In geopolitical terms it's more of a scalpel than a hammer. This is for taking out an emerging threat at short notice based on intelligence developed in the field, not for going up against a prepared opponent with an established ability to respond in kind or worse.
This point is understood, this discussion is about dangers of using this weapon even against somebody without retaliatory capability since the ones with the retaliatory capability can launch counterstrike by mistake since early warning system is not going to be able to distinguish launch of this weapon from the nuclear missile launch.
That's what submarines are for, and it seems far easier to make a cruise missile that goes Mach 3 from a hundred milse off shore than a missile that goes Mach 20 from across the ocean.
The US already has interests all over the world, and China is barely emerging as a world power. They will consider it fair for their influence to grow, and we will see it growing at the expense of ours. China's interests in Africa, its win/win deals with African nations that need industrial know-how and have raw materials to feed Chinese growth, already made the news here in the U.S., if only for a little while. Chinese culture and American culture are different, and as we come into competition for international influence, clever xenophobes on each side will attempt to frame the competition as a showdown between good and evil. Add to that the machinations of people and corporations whose financial interests are at stake, and you have powerful forces pushing for war. It seems naive to think that we won't go to war with China, to hope that we are the first generation that can avoid war under these circumstances.
Then again, it is each generation's duty to hope to rise above the last. I hope that friendly attitudes and cosmopolitan cynicism can combine to keep conflict from flaring up, and to snuff out any little conflagrations that spring up instead of escalating them out of pride and fear. But inevitably we must plan for the opposite contingency. At the very least we must plan for mistrust and tension, and therefore, at the very least we cannot depend on a weapon that is indistinguishable from a first strike. The only reason to develop it is for research purposes.
P.S. Oh, man, isn't it a tempting idea to snuff out your main creditor? Nobody in the Congress has a more realistic plan for getting rid of the national debt.
You make an interesting point, but it seems that current way of thinking is that mutually assured destruction of the nuclear war will prevent the war between US and China.
The US developed plans to go to war with Canada. It is the perpetual imperative of a department of defense to be consider conflict with everyone, especially those nearest military parity.
I know they're very different beasts and in completely different situations, but it's still interesting to remember that Voyager 1, using 30+ yo technology, is currently going about three times as fast as this plane.
ICBMs have been going roughly this speed for a while now, so anti-ballistic missiles either have been useless for a while, or will continue to work. The shuttle goes a good deal faster (mach 25) on re-entry. And as soon as you strip away the need to land and be re-used (the hallmarks of an "airplane"), your anti-super-fast-airplane missiles become much cheaper and faster than the plane, so even a small success rate serves as an effective deterrent in many cases.
This is a tech experiment. It may lead to advances in airplanes, but I highly doubt it is cost-effective compared to an equivalent missile that just slams home.
ICBMs can go fast, but they follow a predictable ballistic trajectory. They can also be intercepted by anti-missile missiles. You will need another scramjet to catch a scramjet while in the atmosphere.
Not necessarily .. reentry vehicles have been able to maneuver as far back as Gemini by rotating (they have a slight amount of lift) -- this works best in the upper atmosphere where small velocity changes can make large changes to your landing zone. Both the US and Russia designed maneuverable warheads to evade each other's ABM systems.
Your point stands, I'd like to clarify that the HTV-2 vehicle[1] is an unpowered glider, boosted to cruise velocity by a rocket stage, not a scramjet. Unfortunately, most of the popular news reporting has used the term "airplane" which usually refers to an aircraft capable of powered flight. Although the eventual goal of the FALCON project is to develop a scramjet-powered strike aircraft, the current record holder is still NASA's X-43[2] with a maximum attained speed of Mach 9.68.
ICBM's fly outside of the atmosphere and they don't turn... IE. they're ballistic. I could see that something designed to hit the predictable path of a ballistic missile at mach 20 would fail to hit an aircraft which can turn at mach 20. (How well this thing can actually turn is another question.)
This is incorrect. Modern ICMB designs include maneuverable reentry vehicles. Even modest accuracy in an ICBM requires at least a minimal amount of course correction in the terminal phase.
But apparently state of the art re-entry vehicles are capable of much more complex maneuvers including 180 degree turns (heading on ground, not the full 3d vector obviously).
The US has had this capability since a research project in the 1980s. Some form of it is deployed on Trident as well as the comparable UK and CH systems.
There is very little published on the topic, but if you start researching the AMaRV project you'll find some details and claims. Of course there's really no way for someone outside the defense community to confirm these claims, but I know of no physical reason why they couldn't be true.
see my comment below: radius of an 8g turn at mach 20 (330 m/s * 20) is 555 km. I choose 8 g because that's roughly what we think a sunburn (ss-n-22) can do, and that thing is built like brick shit-house.
now, to add to that: the radius of a 1 g turn at mach 20 is 4444 km. The radius of the earth is 6378 km. They've got to at least consider orbital mechanics just to hold altitude constant. Able to maneuver and highly maneuverable are two different things. The Titantic was able to maneuver. Just couldn't move fast enough.
Now, let's think about some other fun stuff, everybody join in.
Here's one: at mach 20, you need something along the lines of the shuttle's thermal protection system. We're talking plasma hot. Wrap this thing up in 3 inches of glass and I'll bet you've lost significant payload volume.
In terms of payload, and as someone asked below, "ordinance and yield" Would it actually need any? Smashing mach 20 into a target would yield tremendous kinetic force without explosives.
Same principle as a http://en.wikipedia.org/wiki/Railgun where projectiles travel at 5,400 mph, and the gun can be situated on an aircraft carrier.
On that note, the article above mentions railguns as way to launch spacecraft into orbit: applicable for this Mach 20 plane.
Granted, the 'ballistic' part does decide it. But what says ICBM tech can't be adapted to simply turn slightly while re-entering? It's not like this plane will be making hair-pin turns, I find it extremely hard to believe something with no need to fly back can't match it for maneuverability.
But what says ICBM tech can't be adapted to simply turn slightly while re-entering?
Mostly the letter "B" for "ballistic".
You can turn while flying. You can't turn while falling. You can stick out a little control vane to try to change course a little bit, but at that sort of speed, in that sort of atmospheric density, and bearing in mind that during re-entry anything that is at all pointy will get burned off, I doubt you could do much at all.
Hence adapted, and referring to the tech, not the object. Making a ballistic missile not-ballistic makes it into something else.
That this was a "plane" is inconsequential, and not even interesting, in terms of missiles - that they had at least minimal control at that speed is either a breakthrough, or duplication of existing techniques that can be applied to big-ass missiles (there, swap the B with "Big") more easily and more cheaply than to something designed to be re-used. Which, given the difficulty in adding controllable movement at such speeds to something way more complex than a one-use missile, implies to me that the techniques have existed for a while in cheaper forms, and this is just the first time they've been able to do it and (nearly) recover the device.
That's significant, but it's not a game-changer for missiles or making things go boom.
I think it's mostly there so the Air Force can pretend it will still be relevant in 20 years time. Pilots in planes will be replaced by UAV, or cruise missiles. But they want to cling to the romance of real humans in the sky.
Solely addressing number 2, I think the factor here is time. The strike window for this weapon as I understand it is 1 hour anywhere in the world. Navy SEAL operations on the order of killing Bin Laden have lead times measured in months. Even Tomahawk missiles take time to position (warships) and fire. When it absolutely, positively has to be destroyed or killed within a hour, Mach 20 is the only way to go.
Plus its non-ballistic flight path and high degree of maneuverability probably allows it to evade most anti-aircraft and anti-ballistic missile defenses.
"highly maneuverable" is an odd term here. What's the radius of an 8 g turn at mach 20? 555 km. The diameter is slightly smaller than the N-S length of California.
Sure, but by the same reasoning, you don't need to change your heading by more than a fraction of a degree before the interceptor has to massively change it's intercept trajectory. A scramjet powered missile randomly making slight adjustments around the desired trajectory would make it extremely difficult to intercept.
I wasn't aware that it was a law. I thought it was merely a prohibition put into place by an Executive Order signed by President Ford.
In either case, it seems moot in today's day and age. What's the difference between firing a missile at enemy headquarters with the intention of killing the general and senior staff, and an assassination?
It seems today that 'assassination' is simply pursuing the usual methods of war against a specific target.
In Robert Baer's book "See No Evil" he describes being questioned by the FBI while working for the CIA for allegedly trying to organize an assassination of Saddam Hussein.
There were no basis for the accusations but he understandably pretty unhappy as the penalties for being found guilty could be pretty severe.
Not at all. An unpunished illegal actions is still illegal; you are not _punished_ if you are not caught violating the law. Your phrasing is more pithy, of course.
cruise missiles are often better for assassinations anyway. They are stealthy, cheap, and extremely accurate - a mach-20 super-hot re-entering slug of metal that had to be launched into space isn't really any of those.
I'll put my money on tiny UAV's as the future of assassinations. They're small now and I'd guess in 10 years they'll have really small ones, I mean fly in like a mosquito and blow up John Connor's head before he even sees it small. Short range but all that means if you need another vehicle to get them close, yeah prolly a cruise missile.
Some months ago I observed an object crossing the sky at night from Coventry UK. It crossed the entire extent of the sky in about 2 seconds. It was very high up and had a red glow like that of a jet afterburner. It didn't fade out or change brightness as you might expect of a meteor and wasn't white as you'd expect of a satellite. I wondered at the time if someone was testing a very fast military vehicle. It would be interesting to know what various nations are working on.
does anyone know if they had telemetry to the thing (which is difficult because of the plasma, but used to be possible at least at shuttle speeds from the tail)? or are they hoping some kind of black box survived? and if they had no telemetry is this report inferred from observations of the flight (only)?
[related - does the telemetry problem mean that if something like this ever went into production, it would be largely autonomous?]
The reports I've seensay they had a live datalink (I guess one-way only) which lasted nine minutes. They said they're happy with the data anyway, even though they don't know where it crashed (technically they don't even know it crashed, only that it stopped sending data), so they're clearly not relying on a black-box.
Surveillance camera, faster and less predictable than a satellite (and faster than the SR-71). Nothing can fly as fast inside the atmosphere, no way to lob a missile or artillery at it.
I'd think directed energy weapons (e.g.: lasers) would probably be effective here.
Any Mach-20 vehicle is going to have an extremely limited thermal tolerance, and thermal shielding is likely to be applied specifically to those elements of the vehicle which require it for aerodynamic reasons.
Lasers could acquire and track with the target despite evasive maneuvers better than any kinetic weapon. Though a large-dispersion scatter weapon (ball bearings) would probably be sufficient. Each bb impact would be about the equivalent of a gram or two of TNT.
The US Air Force understands the concept of high speed spy planes with the SR-71 and knows how to deal with intercept attempts. A slight turn takes the plane well away from harm.
[edit] now if the enemy builds its own with the same speed / range then all bets are off
When you're flying in a straight line, which at these speeds this plane, unlike the SR-71, will be doing, it is only a matter of time until another Zoltan Dani comes along and pops it out of the sky.
You and all the down voters are crazy if you don't believe this thing can change directions. Looking at the whole D-21 / SR-71 program for what this do.
It's a turn wide enough to be effectively a straight line over a good deal of countries. We don't have to calculate out trajectories on the backs of notebooks anymore, we have systems that can do that in milliseconds.
This is just one more in a long line of "unshootable"/"unsinkable" projects which will prove the opposite.
Keep in mind that this vehicle was just for collecting data, a conventional rocket did the work to accelerate it to mach 20. There's nothing the HTV-2 can do other than decelerate and maneuver.
http://en.wikipedia.org/wiki/Non-rocket_spacelaunch#Hyperson...
http://www.enotes.com/topic/Tether_propulsion#HASTOL_.E2.80....
This puts the tensile strength necessary into the realm of existing high-strength polymer cables.
If we could build a robust fully-reusable space plane that can go Mach 15, and we could also find a way to rendezvous it with a rotating tether, we could free ourselves from the nastiness of the rocket equation and achieve inexpensive space access.