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  (Source: DARPA)
DARPA's goal is to cut costs and increase convenience

The Defense Advanced Research Projects Agency (DARPA) is looking to create an unmanned vehicle for satellite launches that is faster, cheaper and more convenient than existing systems.

To do this, DARPA has introduced the Experimental Spaceplane (XS-1) program, which encourages the development of a fully reusable unmanned vehicle that would launch satellites into space. It would look, act, and cost more like a traditional plane. 

Current satellite launch technologies can cost hundreds of millions of dollars per flight, and can only fly a few times per year. To top it off, they typically require years of advanced scheduling. 

“We want to build off of proven technologies to create a reliable, cost-effective space delivery system with one-day turnaround,” said Jess Sponable, DARPA program manager heading XS-1. “How it’s configured, how it gets up and how it gets back are pretty much all on the table—we’re looking for the most creative yet practical solutions possible.”

The idea behind XS-1 is to have a vehicle that can operate from a clean pad, use only a small ground crew, and eliminate the need for costly specialized infrastructure.

Also ideal for XS-1 is a reusable first stage that would achieve hypersonic speeds at a suborbital altitude, and at that point, one or more expendable upper stages would detach and deploy a satellite into Low Earth Orbit. The reusable hypersonic aircraft would then make its way back to earth and be prepared for the next flight. 

The rapid turnaround between flights could be done through modular components, durable thermal protection systems and automatic launch/flight/recovery systems.

DARPA's goal is to develop a vehicle capable of flying 10 times in 10 days; reaching speeds of Mach 10+ at least once; launching a representative payload to orbit, and reducing the costs for small payloads by at least a factor of 10 to less than $5 million per flight.

Think you have what it takes to create what DARPA is looking for? The agency is holding an XS-1 Proposers’ Day on Monday, October 7, 2013. You must register to enter, and registration closes October 1. 

Source: DARPA



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RE: In other words
By Solandri on 9/18/2013 5:04:12 PM , Rating: 2
Sadly, this is the line of research the U.S. was pursuing in the late 1950s.
http://en.wikipedia.org/wiki/North_American_X-15

Then the Soviets launched Sputnik. We needed to put something into space too ASAP, the cost didn't matter. This eventually led to huge amounts of research dollars and time being invested in an ultimately inefficient method of putting things into space.

Only now, after a 50 year detour into a dead-end expensive technology, are we finally getting back on track to figuring out a cost-efficient method of getting into space.


RE: In other words
By Reclaimer77 on 9/18/2013 5:38:59 PM , Rating: 1
There is no cost effective way of getting things into space. The problem is physics. Physics dictates that because of Earth gravity, a large portion of your fuel will have to be allocated in the effort to reach escape velocity. There's just no way around this.

Sure you could build a space elevator. But I would be remiss to call it "cost effective", since constructing it would equal the cost of every space launch ever done in the history of mankind and then some.


RE: In other words
By Jeffk464 on 9/18/2013 5:52:46 PM , Rating: 2
You might have a point, orbit velocity is around 17,000mph so putting a rocket on top of an aircraft subtracts about 500-600mph from that 17,000.


RE: In other words
By Reclaimer77 on 9/18/2013 5:57:34 PM , Rating: 1
We just need some method to achieve the needed thrust, without having to design the craft around needing tons and tons of fuel to generate said thrust.

And I have no idea how you do that besides nuclear, like Project Orion. But that has it's own set of problems, and anything nuclear these days is treated like some kind of pariah.


RE: In other words
By maugrimtr on 9/19/2013 11:21:21 AM , Rating: 2
I'm afraid we're stuck with rocket engines for getting to LEO. That means we're constrained by three basic factors: the efficiency of the non-nuclear fuel, the efficiency of the engine, and the weight of the vehicle+fuel at rest.

Nuclear does have a place to be improved on. It's an excellent source of energy whether for heat or electrical power and it can be a component of a really efficient ion engine for as long as the reactive mass lasts.


RE: In other words
By bug77 on 9/19/2013 3:07:58 AM , Rating: 2
I don't think that this is about shaving off 500 of 600mph, but more about avoiding the thicker part of the atmosphere. Just an assumption, I don't have any insider info.


RE: In other words
By Jeffk464 on 9/19/2013 1:47:50 PM , Rating: 2
Yeah, I also noticed that it looks to be a rocket plane so its going to be more than 500-600mph, probably a few thousand mph.


RE: In other words
By JediJeb on 9/20/2013 4:54:36 PM , Rating: 2
Well it said Hypersonic, which is classified as between 3,840-7,680mph. At the upper end of that range you have already knocked off about 1/3 of escape velocity and almost 1/2 of orbital velocity.


RE: In other words
By JediJeb on 9/20/2013 4:56:02 PM , Rating: 2
Oh, and since it is a plane, you can use a lower thrust engine that takes longer to get to that velocity since you are letting the wings provide some of the lift instead of using the engine to shoot more or less straight up.


RE: In other words
By delphinus100 on 9/18/2013 8:56:43 PM , Rating: 2
quote:
Physics dictates that because of Earth gravity, a large portion of your fuel will have to be allocated in the effort to reach escape velocity. There's just no way around this.


Right...what's your point? The cost of fuel isn't what makes space launch expensive. If that were all that mattered, getting to orbit would cost about as much as getting the same mass across the Pacific. Yes it takes 'lots' of fuel, but fuel resources on Earth are also plentiful and cheap.

quote:
Sure you could build a space elevator. But I would be remiss to call it "cost effective", since constructing it would equal the cost of every space launch ever done in the history of mankind and then some.


Now on that, we agree. Space Elevators are useful only to get to geostationary orbit, getting off any lower means generating your own horizontal velocity to stay in orbit, the lower, the more so. Not everyone wants or needs to get to GEO. Getting there is also a slow ride throught eh VanAllen belts along the way (high-thrust orbital transfers and escape departures cut across them quickly), and they're a stationary target for every orbiting object that's not also in geostationary orbit...


RE: In other words
By m51 on 9/19/2013 12:24:49 AM , Rating: 2
The cost of the fuel only accounts for a few tenths of 1% of the cost of the launch. Launch costs are dominated by the cost of the expendable launch vehicle. If you can develop a reusable vehicle you should be able to cut cost to orbit by something on the order of 100 times.

This is exactly the goal of Elon Musk's SpaceX. Their next generation engines will use Liquified Natural Gas as fuel, which is quite cheap, and Liquid Oxygen, which is practically free.

I would expect a reusable first stage design to be similar to Spacex's F9-R, the upper stage designs would be more open ended as it is a less well understood and more difficult problem to solve.


RE: In other words
By Reclaimer77 on 9/19/2013 1:46:38 AM , Rating: 2
I didn't say the cost of the fuel was what made it expensive. Engineering around having to carry X amount of fuel is. Also the weight of so much fuel means you have to have THAT much extra thrust to compensate for it to get into orbit.


RE: In other words
By troysavary on 9/19/2013 5:41:10 AM , Rating: 2
Physics fail. The only reason a rocket takes so much fuel is that they are using pure thrust to climb. A winged vehicle takes far less fuel to attain altitude. It takes a fighter jet enormous amounts of fuel to climb vertically, which is why that is not their preferred method of gaining altitude.

A space uses far less fuel than rocket booster. It doesn't need to be as large to accomplish the same job.


RE: In other words
By mjv.theory on 9/19/2013 7:07:32 AM , Rating: 2
Just about everything you've said is completely wrong, and the irony of starting by saying "physics fail" just beggars belief.

Of the energy/fuel required to reach orbit only about 7-9% is used to get to "space". That is, less than 10% overcoming gravity and atmospheric drag. Any addition of mass for aerodynamic lift (i.e. wings) completely cancels out any advantage gained from that lift.

The other 90+% of the energy/fuel required is to get the upper stage and payload mass to the required orbital velocity of 25,000kph (17,000mph). That is, 90+% of the energy/fuel is used for acceleration , and not for gaining altitude.

Air launch advocates should note that launching from 50,000ft at 600mph will get you less that an extra 5% payload to orbit . So if DARPA want to put a 2000kg payload (3000-5000lbs, not said above, but that is the DAPRA requirement) to LEO, then air launching the required 200 tonne cryogenically fuelled rocket will increase the payload to orbit by less than 100kg. The difficulties of air launch are so often underestimated, usually by the ignorant, who coincidentally also over-estimate the payload to orbit advantages.


RE: In other words
By M'n'M on 9/19/2013 3:13:22 PM , Rating: 2
QFT !!

The goal of this is to decrease the costs by reusing the expensive parts instead of throwing them away each launch. That was also the goal of the STS. The question then is ... have we learned enough to make a truly reusable re-entry vehicle ?


RE: In other words
By Reclaimer77 on 9/20/2013 10:52:01 AM , Rating: 2
quote:
Just about everything you've said is completely wrong, and the irony of starting by saying "physics fail" just beggars belief.


LOL his post was entertaining to read, I'll give him that..


RE: In other words
By JediJeb on 9/20/2013 5:21:01 PM , Rating: 2
But, if you are using a Ramjet engine to get to the launch altitude of 50,000ft you no longer need to carry as much oxidizer which will save some of the weight needed. Not that it will be a huge weight savings, but any reduction in needed weight is a plus.


RE: In other words
By 91TTZ on 9/18/2013 11:48:31 PM , Rating: 2
quote:
Then the Soviets launched Sputnik. We needed to put something into space too ASAP, the cost didn't matter. This eventually led to huge amounts of research dollars and time being invested in an ultimately inefficient method of putting things into space.


Actually a staged disposable rocket is the most efficient system that we have.

While the idea of a reusable spaceplane sounds great on paper it doesn't work well in reality. While you do get to reuse the spaceplane, you end up burning more aluminum and plastic in the form of solid rocket propellant than you get to bring back in the form of the spaceplane. It was also more expensive per launch than disposable rockets.

Long story short, you end up using more material and money trying to make your rocket system reusable.


RE: In other words
By Paj on 9/19/2013 8:15:54 AM , Rating: 2
Not necessarily. The main issue with multi-stage rockets is the weight of all the propellant you have to carry around. Multi stage rockets get around this by jettisoning weight as they rise higher.

The use of a combined air breathing jet/rocket engine is one avenue that is being explored. Take a look at the Skylon - its pretty amazing tech:

http://www.bbc.co.uk/news/science-environment-2333...

The key thing here is that it extracts the oxygen directly from the atmosphere, and cools the incoming air (which gets extremely hot travelling at hypersonic speeds)so it can be used to the engine. It then switches to a rocket-like mode to achieve escape velocity.


RE: In other words
By 91TTZ on 9/19/2013 2:13:03 PM , Rating: 2
While that definitely looks cool, I remember reading an article a while back that explains why air-breathing rockets or spaceplanes don't make sense. They said that the Space Shuttle was almost completely out of the atmosphere within 2 minutes, at which time it discards its solid rocket boosters. The rest of the time is spent accelerating so that it can gain enough velocity to achieve orbit.

A spaceplane would have to gain much of that speed within the atmosphere which presents other challenges. For one, it needs enough atmosphere to give the engine enough oxygen to work, but that atmosphere creates drag which reduces efficiency. Also, that drag creates heat so it limits the speed the aircraft can go without burning up. The Space Shuttle has to come in at a pretty shallow angle when it reenters the atmosphere so it can bleed off speed before it hits the denser air. Otherwise it would burn up.

If the team you linked to can find a way around these obstacles that would be awesome, since the spacecraft would be cheaper and more efficient.


RE: In other words
By JediJeb on 9/20/2013 6:07:57 PM , Rating: 2
quote:
The Space Shuttle has to come in at a pretty shallow angle when it reenters the atmosphere so it can bleed off speed before it hits the denser air. Otherwise it would burn up.


If the Shuttle had been designed to carry enough propellant to decelerate longer it could have gotten around the need for such a massive heat shield. If you can fire a rocket to decelerate to less than 5000mph before hitting atmosphere there would be far less heat generated upon reentry. The Shuttle used the cheap more efficient method of letting the atmospheric drag slow it down, but also needed to be protected from the heat that method generated. It only had to decelerate below orbital velocity and let gravity and friction do the rest.


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