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DARPA's ALASA Could Pave Way For Cheaper, Faster Satellite Launches
hypnosec writes DARPA is all set to take its Airborne Launch Assist Space Access module (ALASA) program to the next level after the program has shown promising results toward its mission of sending 100-pound satellites into low Earth orbit (LEO) for just $1 million per launch."
ALASA is a new program that seeks to streamline production and encourage re-usability and interchangeability in satellite systems.
From your link:
Failures of the 21-meter wingspan, multi-lobe composite material fuel cells during pressure testing ultimately led to its cancellation as a federal program in 2001. Lockheed Martin has conducted unrelated testing, and has had a single success after a string of failures as recently as 2009 using a 2 meter scale model
A 2-meter scale model of a suborbital craft doesn't sound like we're close to SSTO at all.
I don't understand why the idea is being implemented in such a modest manner. The animation has the rocket stage carried aloft for ignition at high altitude by what looks like an F-18. While I don't doubt the performance of the Hornet's engines, wouldn't it make more sense to extend the payload capacity with a larger carrier craft? Say something on the order of the 747-based shuttle carriers?
Absolute ceiling on a Boeing 747 is ~51,000 feet. That's about the service ceiling for most military jets, and their absolute ceiling is much hgher than that. The SR-71 Blackbird had a service ceiling of ~92,000 feet; its absolute ceiling remains classified.
That's 5,000 feet under the service ceiling of the F-14; A Mig-25 on a ballistic arc (after its air-breathing engines were no longer functioning, it was ballistic until it reentered the atmosphere) is recorded to have hit 123,000 feet in 1977. The ballistic arc on an F-18 should be substantially better than that, but I suspect if you want actual numbers, they are classified.
The point is that the first part of getting up there is the hardest, and military and military-grade airgraft are substantially better at getting up higher because they can reach a higher altitude, and can be going multiple Mach at the time they go ballistic (think "muzzle velocity").
So no, a commercial jet is a bad idea.
The single biggest reason is can you see some rich person buying a used one, like John Travolta bought a used 707, and deciding to take a planeload of ceramic coated rebar to orbit and drop it on peoples heads at 22,000 MPH?
Someone could do a lot more damage just by crashing the 707. For that matter, a 1 meter length of #8 rebar is about 4 kilograms, so, at 22,000 MPH would have about 193 MJ of kinetic energy, if it actually reached the ground with the same amount of energy it had before de-orbiting (which would be ridiculous). That's about 8% more than the equivalent mass of gasoline (and, once again, by the time it reaches the surface, it would be a lot less). Of course, gasoline gets to cheat on the energy density factor by using oxygen. You could argue that it's only fair to compare it to something where the energy is entirely self-contained. That's not really valid since the final destination is inside the atmosphere, but we'll give you that one anyway. We'll consider methane, which requires twice its mass in oxygen to combust. That ends up giving it 38.26% of the theoretical maximum of your de-orbiting rebar pieces by mass.
In other words, someone could do a lot more damage just by dropping various sorts of conventional bombs from a 707. Or from a smaller plane for that matter. Or going on foot. Heck, probably just by running around and beating random people with a piece of rebar considering how unlikely it is for the orbitally delivered rebar to both retain significant energy and actually hit a target.
The "rods from god" concept (usually considered with a much larger projectile of the densest practical materials rather than relatively light projectiles prone to tremendous drag like pieces of rebar) is easily shown to be not worthwhile (if you're launching the projectiles from earth with chemical rockets anyway) compared to just about any method of blowing things up. Any physicist or decent engineer with a napkin and a ball point pen can demonstrate it pretty easily. For some reason, the idea keeps coming up.
This doesn't make a dent in cost effectiveness of Falcon 9 or PSLV.
Let us calculate per pound LEO costs for these vehicles:
ALASA: $1M / 100 lb = $10,000 / lb
Falcon 9: $61.2M / 28,991 lb = $2,111 / lb
PSLV: $20M / 7170 lb = $2,789 / lb
Tiny satellites at 100lb can easily tag along with bigger launches on these vehicles. Costs may be even cheaper for such secondary payloads or may even free in some cases. If SpaceX succeeds in first stage reuse, or ISRO per chance succeeds in RLV-TD plans, costs may come further down.
So ALASA sounds like a costly option for small satellites today and in future. But the technology as such may have potential if handled by a better managed private company that works on it as a commercial venture.