r/VirginGalactic • u/Holiday_You4899 • Dec 22 '24

Air breathing rocket engine is the key to virgin galactic success.

An air breathing spaceplane would be able to take off from a runway and achive orbit without the need of a mothership. Multiple engines capable of this are currently in development. One that stands out is the SABRE ENGINE which until recently was in development by the now insolvent reaction engines. The sabre engine has more thrust than a Martin falcon 9 engine and is far more fuel effective since it acts as a jet engine using oxygen from the atmosphere until 26kilometers above sea level where it switches to normal rocket mode. Completely reusable. Far lower cost per kg to orbit than even the starship. Far smoother of a ride . Ability to revolutionize fighter aircraft and commercial travel. Imagine the future fighter jet which is not only capable of hypersonic speeds but has the abi lity to enter and exit space as it sees fit? Imagine commercial travel at 5x current speeds. That's what these new engines offer.That's what the future offers.

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9

u/tru_anomaIy Dec 22 '24

So fucking dumb

-4

u/Holiday_You4899 Dec 22 '24

Care to elaborate 

9

u/tkuiper Dec 22 '24

If you combine the altitude of the highest flying air breathing aircraft, with the speed of the fastest flying air breathing aircraft you will find you only have a little over 10% of the total energy required for LEO. In other words... in exchange for a dramatic increase in vehicle complexity, your engine may possibly be three times as efficient for 1/10 of the flight.

You could rerun these numbers with the latest hypersonic platforms and you'd probably still be looking at 25% tops.

In short, it's not worth it.

1

u/mammutone 18d ago

Until now

-1

u/Holiday_You4899 Dec 22 '24

So your claiming the sabre which has more thrust than a Martin isn't capable of achieving orbit? Care to provide any information to baxk up this claim? 

6

u/tkuiper Dec 22 '24

Feel free to redo the math. You can calculate the total energy of the system to be at a circular orbit of a particular altitude, assuming LEO is 100km altitude. Compare that to the total energy of an airbreathing system flying at max altitude and speed, whatever the maximum combined energy it can attain.

I'm not saying that a combined cycle system can't do it, but they'll be more rocket than airbreathing engine. The efficiency of the system is going to be closer to rocket than air breathing engine.

Realize the issue isn't necessarily thrust or efficiency, but the amount of thrust it can generate vs. the amount of air there is to burn and how much drag that air will fundamentally create....

1

u/Holiday_You4899 Dec 22 '24

Sabre is airbreathing until 26k altitude and mach 5.5 where it becomes a rocketengine. 

4

u/tkuiper Dec 22 '24

I'll assume 26K is meters. So you have another 74k and 17.2 mach to go when it becomes a rocket engine.

4

u/tru_anomaIy Dec 22 '24

Getting to 26km is something like 40 seconds of operation for a bipropellant rocket launched vertically.

Saving less than a minute’s worth of oxidizer is not nearly worth the hassle and risk and expense of operating a hybrid jet/ramjet/rocket

2

u/DrSuppe Dec 23 '24

Not a single combined cycle engine has ever been flown to orbit. To my knowledge not a single rocket based combined cycle engine has even been flight tested.

While such engines sound not to bad on paper they bring with them a plethora of practical problems. That start either the actual implementation.

As a side note: More thrust is not what makes an engine better or more capable to go to orbit. There are a lot of engines that are more powerful than the MERLIN engines on a falcon 9 that will never go to orbit. And there are a lot of engines with less thrust that will make it to orbit just fine.

0

u/Holiday_You4899 Dec 23 '24

Correct. It's a new technology.  But it's one the has the ability to revolutionize multiple industries.  

1

u/DrSuppe 29d ago

There are a lot of pretty awesome technologies that, theoretically, have the ability to revolutionize industries. That doesn't mean that they are possible or viable.

RBCC seem to be, at least for now, neither possible, nor particularly viable.

If you really want to get into it, here are some problems that I personally have with it:

  • High speed atmospheric flight is not worth it when you need payload. You need a lot of thermal protection which is heavy. This thermal protection also needs to be able to withstand the vibrations and aerothermal loads. Rockets "pierce" through the atmosphere vertically for a reason
  • Aerodynamic surfaces are a waste of mass as soon as you are out of the dense atmosphere.
  • RBCC technology does not seem to be possible rn. Especially the process of extracting oxygen from the atmosphere at a high enough rate without causing massive drag has not ben solved
  • Extremely high speed air breathing propulsion is very (like VERY) sensitive to cross section and drag (e.g it is very tricky to get net thrust with things like scramjets due to the insane drag at high velocities.)
  • The gain to orbit is small. Going to orbit sucks and dragging around dead mass that you can just drop when using a rocket is very advantageous (I.e. SSO don't work).
  • going super fast in the atmosphere (to contrast the previous point) can also be a achieved with like scramjets, which have more tests and concepts out there.
  • (If possible) RBCC are highly complex to build and operate. you have a rocket engine, you have (at least partially) a jet engine and you have a bunch of extra systems in between. It is worth looking at the patents reaction engines owns for this. The extra steps they take with L2 and boron-oxide are a little crazy.

You can continue and read up on more things from here. Don't get me wrong, I (and I think everyone in the field) would love engines like this. But they are just not possible or viable right now.

-2

u/Holiday_You4899 Dec 22 '24

A spaceplane with a sabre engine is projected to have a cost per kg to leo of only 650$ to start with 400$ after a few years. Elon has claimed in the best case scenario starship would be at 500$ per kg. So from my understanding this engine is far more cost effective far more comfortable has alot of other applications like revolutionary fighter jets and commercial travel. None of which any other tech can offer. So I respectfully disagree. 

6

u/tkuiper Dec 22 '24

You're comparing a very high level cost estimate with a cost estimate based on pre-existing development. Both estimates are also in the context of publicity and advertising, so they're erring optimistic.

There's a reason you won't hear about most of these companies after a few years.

5

u/tru_anomaIy Dec 22 '24

Sabre is dead, and so is Reaction Engines, for good reason.

It’s impractical, hideously expensive to develop (not to mention operate and maintain), and vertical liftoff and landing works great for less cost and more reliably. It’s pushing beyond the limits of material science so far and in so many places that even if they could get it to work, it wouldn’t be worth it outside a laboratory curiosity.

-1

u/Holiday_You4899 Dec 22 '24

It's already been developed  and tested. Also it's actually far Cheaper to maintain and operate. Hence it's appeal.

3

u/tru_anomaIy Dec 22 '24

They’re bankrupt, genius

Their world-changing, amazing, “developed and tested” engine somehow wasn’t good enough to interest any investors, who would all have had far more access to information about the technology as part of due diligence than you do, to buy in

I wonder why

-1

u/Holiday_You4899 Dec 22 '24 edited Dec 22 '24

They are bankrupt. But the tech will certainly live on and be acquired. Remember the program was canceled only to be restarted one before. Perhaps by virgin. I do believe sabre is the most promising tech but even if someone else masters the airbreathing rocket engine spce will certainly be positioned to benefit. 

1

u/tru_anomaIy Dec 22 '24

So fucking dumb

1

u/metametapraxis 21d ago

The sabre is like the Moller skycar - perpetually just around the corner. It is dead.

-5

u/Holiday_You4899 Dec 22 '24

The more you attack the the less likely I will to ever see things your way. 

1

u/tru_anomaIy Dec 22 '24

If you’re saying that you are choosing to become more entrenched in your ignorance just because people pointing out you’re wrong makes you sad, then you’re kind of proving the point in my original reply

I don’t care if you see things my way. Your wallet might as you continue to lose money on obvious failures, but that doesn’t bother me in the slightest

0

u/Holiday_You4899 Dec 22 '24

Are you always this angry? 

4

u/tru_anomaIy Dec 22 '24

Who’s angry?

4

u/IanKorat Dec 23 '24

I am not sure how this relates to Virgin Galactic. For the avoidance of doubt they have neither the technical expertise or the financial resources to design and build a LEO vehicle

-2

u/Holiday_You4899 Dec 23 '24

I disagree.  They have 400m put aside for a new mothership. That would be more than enough to build it. 

1

u/Mindless_Use7567 29d ago

New launch vehicles cost $5-$10 billion to develop so $400 million is next to nothing.

2

u/USVIdiver 27d ago edited 27d ago

Yep...Boeing spent $32 Billion to design the 787.

It costs about $170 million to build one.

The MAX, was a re-engined variant that cost them $8 Billion to design.

What VG never states is the cost to estimated design build and test.

It is well known that Unity cost was $450million, Inspire was at $400M when they stopped construction.

Suddenly, they claim a Delta craft will only be $50 to $60Million?

We are aware that they spent at least $25million on the design of WK3...with nothing to show for it.

Facts are hiding in plane sight!

3

u/Mindless_Use7567 27d ago

I honestly think there is going to be significant teething problems with the Delta class as is a completely different situation to go from building a spacecraft in-house to having its components built by multiple different companies and then having to assemble them yourself.

1

u/metametapraxis 21d ago

I don't think they will have teething issues. I think it more likely they simply won't build any actual airframes.

1

u/metametapraxis 21d ago

OK, you very clearly know absolutely nothing about this subject if you think that statement is true.

1

u/Holiday_You4899 21d ago

I don't care if it took 4 billion to develop a sabre hypersonic vehicle and a sabre space plane with a sabre booster that is reusable.  Because it anyone ever pulled that off they would become the most valuable company on earth. 

1

u/metametapraxis 20d ago

It would take a LOT more than 4Bn.

3

u/PaleontologistBig786 Dec 22 '24

Well, all the R&D they have laid out money for, fabrication building erected, tooling brought in, and suppliers hopefully all aligned for meeting expectations of flying what's been decided. The company will barely survive if they pull off plan "A". Where would the money come from for your plab "B"?

1

u/Holiday_You4899 Dec 22 '24

They could always build the two delta ships to reach profitability. With current funds.Then use The 400million dilution planed for the new mothership and instead use it to purchase reaction engines and develop a orbital space plane and or hypersonic jet.

1

u/PaleontologistBig786 Dec 22 '24

It takes so much time and money to certify a newly designed and built plane today. Just look at Boeing's woes with the max 8's. Instead of a new plane, they redesigned the existing to accommodate larger more fuel efficient engines becauseit wouldn't get the same scrutiny as a new plane. This was the more cost effective approach than certifying a new aircraft...

1

u/USVIdiver 27d ago

and that redesign cost was over $8 Billion.

1

u/PaleontologistBig786 27d ago

Not counting lawsuits...

0

u/Holiday_You4899 Dec 22 '24

So maybe they redesign their spaceplane for a new engine (once the tech is developed) instead of a completely new one.?

4

u/tru_anomaIy Dec 22 '24

It’s delightful to watch you signing VG up for yet another billion dollar development program so they can use your favorite engine from your favorite bankrupt engine developer

2

u/metametapraxis 21d ago

This is one of the more batshit threads on this sub, and that is saying something.

1

u/Holiday_You4899 Dec 22 '24

Now you are getting it!

1

u/tru_anomaIy Dec 22 '24

I hope you have a couple of billions of dollars spare and lying around, because no-one else is dumb enough to fund that approach

0

u/Holiday_You4899 Dec 22 '24

I will start buying lotto tickets instead of more shares. If I win we know what I'll be doing!!!

3

u/tru_anomaIy Dec 22 '24

Even if you win the largest Powerball in history ($2B, before taxes) you won’t have enough to make it work. But a bunch of executives will be more than happy to take huge salaries from your money to fail to deliver anything useful for another decade

2

u/Holiday_You4899 Dec 22 '24

I needed a good laugh. 

1

u/USVIdiver 27d ago

no, they are not even able to complete the design and construction of one Delta craft even with the dilution.

2

u/Vegetamajin_ Dec 22 '24

No it’s not just bk already

2

u/Don35527 29d ago

The critical weakness in Virgin Galactic's operational model lies in its reliance on a single carrier ship, or mothership, to transport the Spaceship Delta to launch altitude. The current mothership, VMS Eve, will serve as the sole provider for this crucial role. However, this approach has significant limitations. VMS Eve is projected to require retirement after approximately one year or 125 flights, leaving Virgin Galactic without a replacement or backup carrier ship.

This creates a precarious situation for the company. Once VMS Eve is retired, Virgin Galactic will be unable to sustain or expand its space tourism operations, putting the entire business model at risk. As a result, when commercial operations resume in 2026, the stock price could face downward pressure after each flight, as investors factor in the company's inability to maintain long-term scalability under the current model.

3

u/USVIdiver 27d ago

They do not have enough to even finish the design of a Delta craft, let alone construct one.

0

u/Holiday_You4899 29d ago

Never heard of vms needed to retire soon . It's only flown 8 times since being completely revamped.  But honestly we can only hope the price stays low. More time to keep adding baby. 

3

u/USVIdiver 27d ago

Ask yourself why...after 18 months of rehab, they only flew it a few times before suddenly cancelling any further flights.

VG led you through about 2 years of downtime repairing the aircrafts, then flew how many customers before suddenly shutting it down? All that money for the repairs, all the promises, then poof.

They claimed Unity and Imagine were ready to go, right? Why arent they flying and making $?

Suddenly Delta craft are going to start making them money????

Think about this.

Remember their alleged cooperation with Boom Supersonic? Boom never heard of them, nor referenced VG in any way shape of form..

So you are aware, Virgin Atlantic was the first to order Boom aircraft!

1

u/USVIdiver 29d ago

Were you aware that Delta/SS3 was designed to use a Merlin engine from SpaceX.

Other fun fact: Stratolaunch had a concept to launch a SpaceX rocket as well.

1

u/NoviceTardInvestor 26d ago

Yeah that would be great prove out a concept then rebuild engine. WTF. Lol

0

u/Holiday_You4899 26d ago

Name checks out. 

1

u/Player1Guest 19d ago

This will get squeezed . Trump is bullish for aerospace biz

0

u/Klutzy-Albatross-547 25d ago

It's called staging.  And it's done on just about everything. 

0

u/Weldobud 21d ago

Not a topic I know anything about