HAWC (Hypersonic Air-breathing Weapon Concept) and HACM (Hypersonic Attack Cruise Missile)

[sferrin]

so I don't understand the whole attitude around ARRW given its currently facing issues with the most rushed part of its development (booster dev and integration) which any other program, equally rushed, could also suffer from.

From my perspective, I see these failures and can't help being reminded of HyFly, which was cancelled due to failures unrelated to it's propulsion system, and the X-51 which almost didn't get to fly it's most successful flight because of failures not related to it's propulsion system. I worry risk aversion is going to kick in and bye-bye ARRW.

BTW, where does this fit into the hypersonic mix?

Sea Air Space 2021: Boeing Unveils New Hypersonic Cruise Missile Concept - Naval News

At Sea Air Space 2021, the naval defense exposition held near Washington DC, Boeing unveiled a new hypersonic cruise missile concept artist rendering know as HyFly 2 for carrier-based strike fighter.

www.navalnews.com

 

[bring_it_on]

BTW, where does this fit into the hypersonic mix?

Sea Air Space 2021: Boeing Unveils New Hypersonic Cruise Missile Concept - Naval News

At Sea Air Space 2021, the naval defense exposition held near Washington DC, Boeing unveiled a new hypersonic cruise missile concept artist rendering know as HyFly 2 for carrier-based strike fighter.

www.navalnews.com

Boeing is one of the awardees on SCiFiRE so technically it’s in the running but it looks like it will be between Lockheed and Raytheon.

 

[sferrin]

BTW, where does this fit into the hypersonic mix?

Sea Air Space 2021: Boeing Unveils New Hypersonic Cruise Missile Concept - Naval News

At Sea Air Space 2021, the naval defense exposition held near Washington DC, Boeing unveiled a new hypersonic cruise missile concept artist rendering know as HyFly 2 for carrier-based strike fighter.

www.navalnews.com

Boeing is one of the awardees on SCiFiRE so technically it’s in the running but it looks like it will be between Lockheed and Raytheon.

Does Boeing intend to fly theirs or is it just a concept for the trade show? If both Raytheon and LM have successfully flown theirs, I can't imagine anybody giving Boeing the time of day considering their recent track record.

 

[Josh_TN]

On the other hand an air breather probably is an order of magnitude cheaper to produce and likely allows for much easier terminal seeker integration. Mach 5 isn’t really beyond what upper end AAMs have to go through.

 

[bring_it_on]

BTW, where does this fit into the hypersonic mix?

Sea Air Space 2021: Boeing Unveils New Hypersonic Cruise Missile Concept - Naval News

At Sea Air Space 2021, the naval defense exposition held near Washington DC, Boeing unveiled a new hypersonic cruise missile concept artist rendering know as HyFly 2 for carrier-based strike fighter.

www.navalnews.com

Boeing is one of the awardees on SCiFiRE so technically it’s in the running but it looks like it will be between Lockheed and Raytheon.

Does Boeing intend to fly theirs or is it just a concept for the trade show? If both Raytheon and LM have successfully flown theirs, I can't imagine anybody giving Boeing the time of day considering their recent track record.

Just at air shows. If they make the down-select on SciFire then I guess they'll build it.

 

[Vanessa1402]

do we know the minimum altitude needed to launch HAWC? I think there is a limit because the booster need to reach Mach 5 minimum at burn out

 

[Josh_TN]

We do not. I think X-51 was launched at 50,000+ feet, but I don’t think anyone has given out information for HACW. I suspect it’s pretty high; the goal seems to be for the most cost effective possible weapon. I’m guessing they are going to skimp on the booster in favor of a cheaper, shorter, lighter weapon. If your missile has a 500km plus range, you don’t need to be flying under the radar. And if you can pack twenty into a B-52, you’re probably willing to accept launching at 30-50,000 feet for that capability.

 

[sferrin]

BTW, where does this fit into the hypersonic mix?

Sea Air Space 2021: Boeing Unveils New Hypersonic Cruise Missile Concept - Naval News

At Sea Air Space 2021, the naval defense exposition held near Washington DC, Boeing unveiled a new hypersonic cruise missile concept artist rendering know as HyFly 2 for carrier-based strike fighter.

www.navalnews.com

Boeing is one of the awardees on SCiFiRE so technically it’s in the running but it looks like it will be between Lockheed and Raytheon.

Does Boeing intend to fly theirs or is it just a concept for the trade show? If both Raytheon and LM have successfully flown theirs, I can't imagine anybody giving Boeing the time of day considering their recent track record.

Just at air shows. If they make the down-select on SciFire then I guess they'll build it.

I don't see how they make the down-select given both the other guys have successfully flown theirs.

 

[bring_it_on]

BTW, where does this fit into the hypersonic mix?

Sea Air Space 2021: Boeing Unveils New Hypersonic Cruise Missile Concept - Naval News

At Sea Air Space 2021, the naval defense exposition held near Washington DC, Boeing unveiled a new hypersonic cruise missile concept artist rendering know as HyFly 2 for carrier-based strike fighter.

www.navalnews.com

Boeing is one of the awardees on SCiFiRE so technically it’s in the running but it looks like it will be between Lockheed and Raytheon.

Does Boeing intend to fly theirs or is it just a concept for the trade show? If both Raytheon and LM have successfully flown theirs, I can't imagine anybody giving Boeing the time of day considering their recent track record.

Just at air shows. If they make the down-select on SciFire then I guess they'll build it.

I don't see how they make the down-select given both the other guys have successfully flown theirs.

That's what i think as well. Boeing has no relevant recent experience that can seal this for them.

 

[mkellytx]

We do not. I think X-51 was launched at 50,000+ feet, but I don’t think anyone has given out information for HACW. I suspect it’s pretty high; the goal seems to be for the most cost effective possible weapon. I’m guessing they are going to skimp on the booster in favor of a cheaper, shorter, lighter weapon. If your missile has a 500km plus range, you don’t need to be flying under the radar. And if you can pack twenty into a B-52, you’re probably willing to accept launching at 30-50,000 feet for that capability.

Balls 50 was just shy of 50,000 ft., 49,000 or so was about as much as she could do and still land at a safe weight, and she took off with barely enough gas to do the mission. I helped plan that mission, have the patch, the program was a bit of a science experiment. Safe bet for HACW is mid 30's, the jet is real happy at that altitude carrying a bunch of stuff on the HSAB's.

 

[bring_it_on]

It has been reported that the F-15 is going to be the initial platform for HACM which is the operational prototype that will be fielded in FY-27. HAWC is not a weapon nor meant to be one.

 

[Josh_TN]

It has been reported that the F-15 is going to be the initial platform for HACM which is the operational prototype that will be fielded in FY-27. HAWC is not a weapon nor meant to be one.

I has assumed B-52 would be the initial carrier; do you have a link for the F-15 being the initial platform? Presumably the Echos?

 

[Josh_TN]

We do not. I think X-51 was launched at 50,000+ feet, but I don’t think anyone has given out information for HACW. I suspect it’s pretty high; the goal seems to be for the most cost effective possible weapon. I’m guessing they are going to skimp on the booster in favor of a cheaper, shorter, lighter weapon. If your missile has a 500km plus range, you don’t need to be flying under the radar. And if you can pack twenty into a B-52, you’re probably willing to accept launching at 30-50,000 feet for that capability.

Balls 50 was just shy of 50,000 ft., 49,000 or so was about as much as she could do and still land at a safe weight, and she took off with barely enough gas to do the mission. I helped plan that mission, have the patch, the program was a bit of a science experiment. Safe bet for HACW is mid 30's, the jet is real happy at that altitude carrying a bunch of stuff on the HSAB's.

Very informative as always; thanks for your expertise.

 

[bring_it_on]

It has been reported that the F-15 is going to be the initial platform for HACM which is the operational prototype that will be fielded in FY-27. HAWC is not a weapon nor meant to be one.

I has assumed B-52 would be the initial carrier; do you have a link for the F-15 being the initial platform? Presumably the Echos?

“This budget completes prototyping of the Air Force Air-launched Rapid Response Weapon, ARRW, and fields the Hypersonic [Attack] Cruise Missile, HACM, on the F-15 in 2027,” Boxall said.

Broken ARRW: Hypersonics Program Faces Uncertain Future after 2023 | Air & Space Forces Magazine

The Air Force is not buying any ARRW missiles in 2023, as the Air-launched Rapid Response Weapon program faces major hurdles.

www.airforcemag.com

 

[Josh_TN]

Weird, I'd just assume they'd want it on the strategic bombers. It would greatly increase the number that could be employed and the ranges they could be deployed at. With China being the peer competitor, I wouldn't have thought the new wiz-bang missile would be (initially) limited to tactical in theater aircraft. Perhaps they are envisioning a more modest initial deployment where the capacity of the B-52 wouldn't be useful.

 

[bring_it_on]

Weird, I'd just assume they'd want it on the strategic bombers. It would greatly increase the number that could be employed and the ranges they could be deployed at. With China being the peer competitor, I wouldn't have thought the new wiz-bang missile would be (initially) limited to tactical in theater aircraft. Perhaps they are envisioning a more modest initial deployment where the capacity of the B-52 wouldn't be useful.

JASSM ER is roughly 1K km, and ARRW is expected to be in a similar ballpark as far as range is concerned. Those are the two options for strategic bombers. Something that is possibly half the range (closer to the range of the original JASSM) is probably better suited for strike fighters especially since it looks like they'd be able to carry multiple such weapons.

 

[sferrin]

Weird, I'd just assume they'd want it on the strategic bombers. It would greatly increase the number that could be employed and the ranges they could be deployed at. With China being the peer competitor, I wouldn't have thought the new wiz-bang missile would be (initially) limited to tactical in theater aircraft. Perhaps they are envisioning a more modest initial deployment where the capacity of the B-52 wouldn't be useful.

JASSM ER is roughly 1K km, and ARRW is expected to be in a similar ballpark as far as range is concerned. Those are the two options for strategic bombers. Something that is possibly half the range (closer to the range of the original JASSM) is probably better suited for strike fighters especially since it looks like they'd be able to carry multiple such weapons.

I just hope they don't give up on ARRW without even having flown the glider. (It would be par for the course though.)

 

[bring_it_on]

Unless there are catastrophic failures in upcoming booster tests, the AF has fully funded all ARRW flight testing through End of the fiscal year. They’ve even requested R&D money in FY-23 testing to make up for the delay so if all that holds, they should test the AUR sometime in Nov- Dec timeframe.

 

[Josh_TN]

Weird, I'd just assume they'd want it on the strategic bombers. It would greatly increase the number that could be employed and the ranges they could be deployed at. With China being the peer competitor, I wouldn't have thought the new wiz-bang missile would be (initially) limited to tactical in theater aircraft. Perhaps they are envisioning a more modest initial deployment where the capacity of the B-52 wouldn't be useful.

JASSM ER is roughly 1K km, and ARRW is expected to be in a similar ballpark as far as range is concerned. Those are the two options for strategic bombers. Something that is possibly half the range (closer to the range of the original JASSM) is probably better suited for strike fighters especially since it looks like they'd be able to carry multiple such weapons.

I just hope they don't give up on ARRW without even having flown the glider. (It would be par for the course though.)

On that note, something I always wondered...has DARPA never had a publicized test of TBG? To the best of my knowledge, that is the case, though that wouldn't exclude testing that simply wasn't disclosed.

 

[bring_it_on]

They have either done some testing and haven’t announced it or rolled the TBG flight testing into the ARRW program in which case the glider will fly in December.

 

[Josh_TN]

They have either done some testing and haven’t announced it or rolled the TBG flight testing into the ARRW program in which case the glider will fly in December.

There's an ARRW test announced for December?

 

[bring_it_on]

They have either done some testing and haven’t announced it or rolled the TBG flight testing into the ARRW program in which case the glider will fly in December.

There's an ARRW test announced for December?

The ARRW all up round test is expected by December under the assumption that booster test firings successfully conclude by then.

Now, “due to recent flight test anomalies,” the first test of the entire missile has shifted to the period between Oct. 1 and Dec. 30 with additional tests planned later in the next fiscal year, according to the Air Force statement. It said the service intends to declare an early operational capability “after successful demonstration of operational utility” through tests of the complete missile after the booster demonstrations. https://t.co/xLW9lbqVMS

 

[Ronny]

US tested hypersonic missile in mid-March but kept it quiet to avoid escalating tensions with Russia

The US successfully tested a hypersonic missile in mid-March but kept it quiet for two weeks to avoid escalating tensions with Russia as President Joe Biden was about to travel to Europe, according to a defense official familiar with the matter.

edition.cnn.com

"The official offered scant details of the missile test, only noting the missile flew above 65,000 feet and for more than 300 miles. But even at the lower end of hypersonic range -- about 3,800 miles per hour -- a flight of 300 miles is less than 5 minutes."

HAWC and CPS carrying the entire weight of the US hypersonic test programs.

a bit strange but how long did HAWC flew?
Was it over 300 miles (482 km) or was it over 300 nautical miles (556 km)?
There seem to be some conflicting information, the first time i heard about the second test, they said it flew over 300 miles, but now there are many source indicate the missiles in fact flew over 300 nautical miles

After release from a carrier aircraft, the Lockheed Martin-produced hypersonic vehicle was boosted to the launch envelope of its Aerojet Rocketdyne air-breathing scramjet engine
At this point, the scramjet took over and “quickly accelerated” the vehicle to a cruise speed over Mach 5, which it maintained for an “extended period of time”. It reached altitudes higher than 65,000ft and travelled over 300nm (556km).

US conducts second successful HAWC hypersonic test

The US Defense Advanced Research Projects Agency (DARPA) has conducted a second successful test flight of its Hypersonic Air-Breathing Weapon Concept (HAWC) vehicle.

www.flightglobal.com

The vehicle quickly accelerated to and maintained cruise faster than Mach 5 for an extended period of time. The craft reached altitudes exceeding 65,000 feet while flying over 300 nautical miles.

DARPA details HAWC flight test progression - Homeland Preparedness News

The Defense Advanced Research Projects Agency (DARPA) recently detailed the second successful flight test of the Lockheed Martin Hypersonic Air-breathing Weapon Concept (HAWC). “This Lockheed Martin HAWC flight test successfully demonstrated a second design that will allow our warfighters to …...

homelandprepnews.com

https://www.darpa.mil/news-events/2022-04-05

 

[bring_it_on]

If the official darpa press release states 300 nautical miles, then that should settle it. It doesn’t really get more official than that unless the PM holds a press conference and claims something different.

 

[TomcatViP]

I made the computation with the map that was released at the time, using geo coordinates, b/w release and splash down locations.

It should be somewhere in this thread or one related but the 500/600km is accurate.

 

[Ronny]

Two recent developments in hypersonics portend the arrival of affordable, long-range hypersonic systems to strengthen national security.

In September, Raytheon Missiles & Defense, in partnership with Northrop Grumman, successfully completed the first flight test of a scramjet-powered Hypersonic Air-breathing Weapon Concept, or HAWC (pronounced “hawk”), for the Defense Advanced Research Projects Agency and the US Air Force. The HAWC flight test data will help validate affordable system designs and manufacturing approaches that will field air-breathing hypersonic missiles to our warfighters in the near future, according to DARPA.

And in February, Defense Secretary Lloyd Austin met with more than a dozen defense-company CEOs to discuss the need to accelerate development of hypersonics to counter Chinese and Russian advances in this area.

In this Q&A with Wes Kremer, president of Raytheon Missiles & Defense, we discuss the HAWC program, the difference between air-breathing and boost-glide hypersonics, and how the organization is using digital engineering for design and test validation.

Breaking Defense: Many times, but not always, these sort of DARPA demonstration programs lead to a procurement program. Is there a program on the horizon that HAWC was specifically developed for?

Kremer: You’re right, taking a success out of a DARPA program and converting that into a program of record for one of the services is always the goal. For HAWC, that program of record will be the Air Force’s Hypersonic Attack Cruise Missile, or HACM. It is part of the FY22 budget.

Last year, we received a contract from the Air Force for the Southern Cross Integrated Flight Research Experiment, or SCIFiRE. This program is the bridge between HAWC and HACM, resulting in the design and technology demonstration for a hypersonic cruise missile. It’s a bilateral effort between the U.S DoD and the Australian Department of Defense to advance air-breathing hypersonic technologies.

Air-breathing hypersonics: A new tactical capability to counter evolving threats - Breaking Defense

Because DARPA’s Hypersonic Air-breathing Weapon Concept doesn’t exit and re-enter the atmosphere like boost-glide hypersonics, it is less reliant on costly exotic materials for thermal management.

breakingdefense.com

 

[TomcatViP]

Notice also the good definition of Digital engineering.

 

[mkellytx]

Notice also the good definition of Digital engineering.

It's a very good high level view, not surprising as NG and Raytheon are both pretty good in the DE and model based SE space. We even poached one of the Raytheon VP's to bring that expertise into my current industry. It really is amazing to see all of that verification and validation stuff we dreamed about in 2006-2010 come true a decade and a half later.

 

[Forest Green]

Navy's next-gen, ship-killing missile will be a hypersonic weapon dubbed HALO - Breaking Defense

The fiscal 2023 budget request is the first to outline crucial details about the next increment of OASuW, including its hypersonic capability.

breakingdefense.com

 

[Josh_TN]

It seems to me the USNs primary problem is shrinking down a HAWC like capability into a 15’ package. I think they are going to have to use some exotic materials for the booster and make integral to the thrust chamber to reduce length.

 

[sferrin]

It seems to me the USNs primary problem is shrinking down a HAWC like capability into a 15’ package. I think they are going to have to use some exotic materials for the booster and make integral to the thrust chamber to reduce length.

Why exotic? They did it in 1980. ASALM went Mach 5.4 and fit inside the envelope.

 

[Josh_TN]

It seems to me the USNs primary problem is shrinking down a HAWC like capability into a 15’ package. I think they are going to have to use some exotic materials for the booster and make integral to the thrust chamber to reduce length.

Why exotic? They did it in 1980. ASALM went Mach 5.4 and fit inside the envelope.

I think they will need something more energetic/efficient than that by a wide margin. I think ASALM only had to accelerate to Mach 2; HACM/HALO will need to make at least Mach4 and probably achieve more altitude than ASALM. Perhaps a PDE type booster could provide the necessary moxie.

 

[MihoshiK]

It seems to me the USNs primary problem is shrinking down a HAWC like capability into a 15’ package. I think they are going to have to use some exotic materials for the booster and make integral to the thrust chamber to reduce length.

Why exotic? They did it in 1980. ASALM went Mach 5.4 and fit inside the envelope.

I think they will need something more energetic/efficient than that by a wide margin. I think ASALM only had to accelerate to Mach 2; HACM/HALO will need to make at least Mach4 and probably achieve more altitude than ASALM. Perhaps a PDE type booster could provide the necessary moxie.

His point is literally that the USN had a hypersonic weapon that did all of this, and didn't need special materials. Granted, barely hypersonic, but it got there without the latest whiz-bang superduper energetics.

And that was 40 years ago. The USN should be able to do just as well or better today, and without special materials.

 

[bring_it_on]

It seems to me the USNs primary problem is shrinking down a HAWC like capability into a 15’ package. I think they are going to have to use some exotic materials for the booster and make integral to the thrust chamber to reduce length.

USN had a projected that looked to do just that i.e. develop a new booster that would allow them to operate the HAWC aboard CVN's. The service has terminated that effort in FY-2023, and is instead pursuing HALO which is going to be a navy specific design from the ground up. Given digital engineering advances, and the fact that the Navy has an interest in SciFire, picking up from that and entering HALO (very similar to what USAF is doing with HACM) seems like a good strategy.

 

[sferrin]

It seems to me the USNs primary problem is shrinking down a HAWC like capability into a 15’ package. I think they are going to have to use some exotic materials for the booster and make integral to the thrust chamber to reduce length.

Why exotic? They did it in 1980. ASALM went Mach 5.4 and fit inside the envelope.

I think they will need something more energetic/efficient than that by a wide margin. I think ASALM only had to accelerate to Mach 2; HACM/HALO will need to make at least Mach4 and probably achieve more altitude than ASALM. Perhaps a PDE type booster could provide the necessary moxie.

Do we know if they're using a pure scramjet or a dual-combustion ramjet? The latter only requires ramjet speeds to begin operation.

 

[Josh_TN]

It seems to me the USNs primary problem is shrinking down a HAWC like capability into a 15’ package. I think they are going to have to use some exotic materials for the booster and make integral to the thrust chamber to reduce length.

Why exotic? They did it in 1980. ASALM went Mach 5.4 and fit inside the envelope.

I think they will need something more energetic/efficient than that by a wide margin. I think ASALM only had to accelerate to Mach 2; HACM/HALO will need to make at least Mach4 and probably achieve more altitude than ASALM. Perhaps a PDE type booster could provide the necessary moxie.

His point is literally that the USN had a hypersonic weapon that did all of this, and didn't need special materials. Granted, barely hypersonic, but it got there without the latest whiz-bang superduper energetics.

And that was 40 years ago. The USN should be able to do just as well or better today, and without special materials.

I am aware of the performance of the ASALM and it is a shame it wasn't further developed. However I suspect its borderline (and accidental) hypersonic performance came at a major range reduction. It's performance envelop was also much wider than any pure scramjet could accomplish - HAWC is rumored to have no moving parts in its engine, which means it has a relatively narrow speed/altitude range it's inlet and combustion chamber can operate in that will require a much more energetic booster to reach. For HACM, I suspect the USAF is unconcerned with the length of the weapon (HAWC was rumored to be ~20 feet) so they can use a wider, external booster. The USN is limited to 15 feet by weapons elevators, or else it would need the weapon to be assembled on deck which I doubt is an acceptable solution for them. Alternatively the USN might be able to shrink down the actual air vehicle's length. But my understanding is that completely burning JP-7 at supersonic air stream speeds requires a longer combuster than say the hydrogen fueled X-43, so shorting the engine maybe very difficult.

 

[Josh_TN]

It seems to me the USNs primary problem is shrinking down a HAWC like capability into a 15’ package. I think they are going to have to use some exotic materials for the booster and make integral to the thrust chamber to reduce length.

Why exotic? They did it in 1980. ASALM went Mach 5.4 and fit inside the envelope.

I think they will need something more energetic/efficient than that by a wide margin. I think ASALM only had to accelerate to Mach 2; HACM/HALO will need to make at least Mach4 and probably achieve more altitude than ASALM. Perhaps a PDE type booster could provide the necessary moxie.

Do we know if they're using a pure scramjet or a dual-combustion ramjet? The latter only requires ramjet speeds to begin operation.

I think the budget document gave no specifics. The previous "Screaming Arrow" requirement was for hypersonic speed but left the exact solution up to the vender, so hypothetically a ramjet or combined cycle ram/scramjet solution would be acceptable. Practically I think they will want to opt for scramjet only, building on the HACW demonstrator and its 3D printed engine arrangement that has no moving parts. That would be a big enabler for cost, reliability, and east of manufacture. But that is just my personal opinion; no details have been given.

 

[sferrin]

But my understanding is that completely burning JP-7 at supersonic air stream speeds requires a longer combuster than say the hydrogen fueled X-43, so shorting the engine maybe very difficult.

I seem to recall reading that the X-51's engine circulated the fuel through a heat exchanger (engine walls?) to "crack" the fuel into lighter elements to allow the use of a shorter burn path.

 

[Josh_TN]

But my understanding is that completely burning JP-7 at supersonic air stream speeds requires a longer combuster than say the hydrogen fueled X-43, so shorting the engine maybe very difficult.

I seem to recall reading that the X-51's engine circulated the fuel through a heat exchanger (engine walls?) to "crack" the fuel into lighter elements to allow the use of a shorter burn path.

Did the article mention that it used some kind of catalyst for that? I would think you'd need a platinum surface or something. Clever solution if they managed it.

 

[sferrin]

But my understanding is that completely burning JP-7 at supersonic air stream speeds requires a longer combuster than say the hydrogen fueled X-43, so shorting the engine maybe very difficult.

I seem to recall reading that the X-51's engine circulated the fuel through a heat exchanger (engine walls?) to "crack" the fuel into lighter elements to allow the use of a shorter burn path.

Did the article mention that it used some kind of catalyst for that? I would think you'd need a platinum surface or something. Clever solution if they managed it.

Yep. "Thermal cracking" is the phrase to look for.

"How Pratt & Whitney achieves this vaporized fuel condition is why the X-51 engine is a revolutionary flight weight design, nearly ready for scale-up in an operational design for a Prompt Global Strike missile.

The JP-7 fuel is first pumped into tiny passages behind engine walls at the front of the engine. It flows behind the walls of hot engine structure cooling the engine until it reaches the rear of the scramjet. There is more going on than cooling, however.

The passages behind the engine walls are coated with a catalyst material. As the JP-7 absorbs heat from the structure, the fuel's temperature and pressure rises until the catalyst reacts with the JP-7 and "cracks" it, literally breaking it down into smaller hydrocarbon components like hydrogen, ethylene and methane.

At the rear of the engine, the cracked fuel is collected and reverses course, now being pumped forward where ,as a vapor, it is sprayed into the combustor and ignited. The combustion products then expand tremendously in the rear nozzle, where they fire out of the scramjet creating about 1,000 lb. of thrust. That does not sound like much, but in a test engine at 60,000-100,000 ft. with the vehicle already moving at Mach 4 at ignition, it is enough thrust to continuously accelerate the vehicle past Mach 6, if all goes well."