FALCon---DLR

[Tywin]

A new method for a reusability system...

I don't know if the name of the program is some kind the homenage to SpaceX 


https://spacenews.com/germany-begins-reusability-study-to-capture-rockets-in-midair-and-land-them-with-a-plane/

It's not look too much simple, this system...

[gosnold]

I did not think you could design something more convoluted than ULA's SMART reuse...

[Steven Pietrobon]

I did not think you could design something more convoluted than ULA's SMART reuse...

ESA's Adeline is pretty close, if not more convoluted! Expendable solid boosters, separable engine section with wings and propellers for boostback and flyback landing on runway and expendable second stage.

[ChrisWilson68]

From the article:

Sippel said the idea of capturing a rocket stage on descent came from evaluations of how to save mass on the rocket. Landings like those SpaceX conducts with the Falcon 9 booster require extra fuel to propulsively slow the vehicle when it returns to Earth. By equipping a booster with wings and gliding it to a recovery aircraft, the rocket stage can use more fuel to deliver a payload into orbit, Sippel said.

“If we tow it back, we save on the mass of the complete propulsion system for fly back,” he said. “That provides a performance advantage.”

It seems foolish to me.  When doing high-levell trades, they are likely underestimating all the mass they'll have to add to make this work.  I think it's likely they'll actually add more mass than just doing it with extra fuel, as SpaceX and Blue Origin are doing.

But, even if they could get a small mass savings, there's no way it's worth all this extra complexity.  The fact that they need to have a special plane to fly out to retrieve it by itself is a deal-breaker.

There's just no way this makes for a lower-cost system than the SpaceX and Blue Origin approach.

[ChrisWilson68]

I don't know if the name of the program is some kind the homenage to SpaceX  ;D

In the article, they claim it's not a homage to SpaceX:

Sippel said the FALCon name, while similar to SpaceX’s Falcon 9 rocket, had a different source of inspiration.

“It’s not anything to do with the Falcon rocket of SpaceX,” he said. “What is behind FALCon is really the Falcon bird. The Falcon bird goes into a dive maneuver to capture other birds or animals, so it is really inspired by the Falcon bird.”

Which is really unfortunate.  They would have been smarter to take inspiration from SpaceX's Falcon.

[ncb1397]

Reminds me of Gremlins:

[Steven Pietrobon]

That are other birds that capture their prey in the air, like Hawk and Eagle.

http://idahoptv.org/sciencetrek/topics/birds_of_prey/facts3.cfm

[ulm_atms]

From the article:

Sippel said the idea of capturing a rocket stage on descent came from evaluations of how to save mass on the rocket. Landings like those SpaceX conducts with the Falcon 9 booster require extra fuel to propulsively slow the vehicle when it returns to Earth. By equipping a booster with wings and gliding it to a recovery aircraft, the rocket stage can use more fuel to deliver a payload into orbit, Sippel said.

“If we tow it back, we save on the mass of the complete propulsion system for fly back,” he said. “That provides a performance advantage.”

It seems foolish to me.  When doing high-levell trades, they are likely underestimating all the mass they'll have to add to make this work.  I think it's likely they'll actually add more mass than just doing it with extra fuel, as SpaceX and Blue Origin are doing.

But, even if they could get a small mass savings, there's no way it's worth all this extra complexity.  The fact that they need to have a special plane to fly out to retrieve it by itself is a deal-breaker.

There's just no way this makes for a lower-cost system than the SpaceX and Blue Origin approach.

The better savings is building the rockets with enough power to be reused in the first place so that the extra fuel for landing isn't a payload weight to orbit issue.  The reusable directioned providers seem to be doing that.  I just don't understand why so many other groups keep going..."but but...that cuts into payload mass!!!"  To which I say..."If you build it big enough...IT DOESN'T MATTER!!"

F9 has shown that it can launch just about anything out there currently and still recover the 1st stage(FH more so on the just about anything part...and that's three 1st stages!!)...so the extra fuel/payload penalty they are complaining about means nothing in the grand scheme of things.  SH/SS will be the entire rocket re-used...and how did they do that???  Bigger rocket to account for reusability requirements!!

And as people have said, fuel is the cheap part.  If you just need more fuel to make it reusable...that's a much cheaper route then adding a ton of complexity....which is the ENTIRE point of reusability in the long run....cheaper prices.

What I find sad is that some groups can't or won't accept what is currently going on.  Ostrich in the ground sort of thing.

And as far as the stage to plane landing and transport idea....it's a reverse Pegasus!  Would be fun to watch live though the first time they tried. 

[Asteroza]

Reminds me of Gremlins:

The capture mechanism is very close to the Gremlins capture mechanism, which is probably due to convergent design principles.

While people moan and groan about this being rube goldberg, it does solve a specific problem, which is your ground track having no landing sites (which is pretty common for east bound coastal spaceports). Depending on the nature of the tow back to an airport, they may be able to heavily cheat and have the tow craft disengage on final approach to the runway if things look good (which provides a go-around ability without an atmospheric propulsion system on the booster).

You do take the hit from carrying the glider wing on the booster though. If your spaceport is crowded enough to make a VTOL booster landing pad not viable due to other operators not wanting to be near the blast zone (this sort of occurred with a ULA launch being stuck in vertical integration and somewhat exposed next to SpaceX and saying no to a SpaceX launch), then having the booster come back elsewhere might be an acceptable alternative.

[ChrisWilson68]

it does solve a specific problem, which is your ground track having no landing sites (which is pretty common for east bound coastal spaceports).

I don't know about that.  If your ground track doesn't have a landing site -- build a landing site. :-)  If people are worried about the booster crashing off the landing site, you'd have the same risk with mid-air capture.  If the mid-air capture goes wrong, the booster can still make a big hole in the ground out of someone's house.

[TrevorMonty]

From the article:

Sippel said the idea of capturing a rocket stage on descent came from evaluations of how to save mass on the rocket. Landings like those SpaceX conducts with the Falcon 9 booster require extra fuel to propulsively slow the vehicle when it returns to Earth. By equipping a booster with wings and gliding it to a recovery aircraft, the rocket stage can use more fuel to deliver a payload into orbit, Sippel said.

“If we tow it back, we save on the mass of the complete propulsion system for fly back,” he said. “That provides a performance advantage.”

But, even if they could get a small mass savings, there's no way it's worth all this extra complexity.  The fact that they need to have a special plane to fly out to retrieve it by itself is a deal-breaker.

So a modified civil plane eg 747, is more complex than modified landing barge or ship with associated support vessels.
Don't forget port facilities and ground transport systems to get it back to pad.

I think its clever idea, definitely worth small proof of concept demo. Also recovery isn't affected by sea conditions. Wouldn't scale to likes of NG but fine for small to medium LVs or side boosters of larger LVs.

[TrevorMonty]

The capture process shouldn't be any different airborne refuelling, which is routine in airforce. Only difference is booster will be gliding so its upto tow aircraft to match glide path of booster.

[Asteroza]

it does solve a specific problem, which is your ground track having no landing sites (which is pretty common for east bound coastal spaceports).

I don't know about that.  If your ground track doesn't have a landing site -- build a landing site. :-)  If people are worried about the booster crashing off the landing site, you'd have the same risk with mid-air capture.  If the mid-air capture goes wrong, the booster can still make a big hole in the ground out of someone's house.

Since most coastal launch sites don't have a handy island downrange, your options are limited to a floating runway (such as the megafloat demo, but redesigned for offshore use, much like the old US Navy mobile offshore base concepts), or you are landing vertically on a barge or platform. The bit about crashing at the landing site is when you are doing a RTLS landing, and the landing pad is near existing launchpads. Other customers/operators may find that unacceptable. If you commit to vertical landing nowhere near the launchpad, then you might as well use a barge downrange if still committed to vertical landing. The fact is, most spaceports have a nearby airport that is still far enough away that the launchpad operators don't break out into a cold sweat at the thought of RTLS boosters landing near their pads.

[envy887]

From the article:

Sippel said the idea of capturing a rocket stage on descent came from evaluations of how to save mass on the rocket. Landings like those SpaceX conducts with the Falcon 9 booster require extra fuel to propulsively slow the vehicle when it returns to Earth. By equipping a booster with wings and gliding it to a recovery aircraft, the rocket stage can use more fuel to deliver a payload into orbit, Sippel said.

“If we tow it back, we save on the mass of the complete propulsion system for fly back,” he said. “That provides a performance advantage.”

But, even if they could get a small mass savings, there's no way it's worth all this extra complexity.  The fact that they need to have a special plane to fly out to retrieve it by itself is a deal-breaker.

So a modified civil plane eg 747, is more complex than modified landing barge or ship with associated support vessels.
Don't forget port facilities and ground transport systems to get it back to pad.

I think its clever idea, definitely worth small proof of concept demo. Also recovery isn't affected by sea conditions. Wouldn't scale to likes of NG but fine for small to medium LVs or side boosters of larger LVs.

Landing is still affected by downrange weather. Snagging a glider in a thunderstorm isn't going to be any easier than landing on a barge in high seas.

Barges are also pretty cheap compared to 747s, although I would not say that is a deal breaker.

Why can't this use glideback like Phantom Express? (Edit: the later papers show downrange distances of 500 to 900 km, which is probably beyond the range glideback can do. Phantom Express will probably stage slower, and the Boeing graphics show it with a larger wing that probably has a larger dry mass but also better glideslope.)

[Prettz]

You do take the hit from carrying the glider wing on the booster though.

Don't forget all the landing gear.

[envy887]

“If we tow it back, we save on the mass of the complete propulsion system for fly back,” he said. “That provides a performance advantage.”

This shows that DLR still doesn't get the advantages of dial-a-landing. Falcon 9 is actually 3 different sized rockets in one:

- a ~10 t rocket with RTLS
- a ~15 t rocket with ASDS
- a ~20 t rocket with expended booster.

That cost and payload flexibility comes from being able to bolt on some hardware for booster recovery.

If you go with horizontal glideback, you have to stress the booster for horizontal landings, and also the recovery components are integral structural components instead of bolt-on. So you can't get maximum expendable performance without designing and building a whole separate expendable booster... or throw away all the recovery hardware cost and mass for little extra benefit.

So you end up building a giant rocket to cover your biggest payloads with recovery, and operating it with constant costs for the entire payload mix.

[envy887]

The full text of the paper is available here:

https://elib.dlr.de/114960/1/IAC17-D2.4.4.pdf

The inert mass ratios graph is attached. The IAC air capture method has a lower mass ratio at MECO, however a larger proportion of the mass is hardware rather than fuel.

That means that the same size vehicle cannot be expended for more performance, and also will be more expensive since hardware has a higher cost than fuel.

[Notaris]

The latest paper on their in-air-capturing work seems to be from end november 2018:

https://elib.dlr.de/125921/

At the same conference, they also presented their view on the various RLV options (winged and non-winged):

https://elib.dlr.de/125063/

[Notaris]

A new method for a reusability system...

[..]

According to the HISST paper of late 2018, the method is not all that new. Is seems to date back to 2001, so a rather "old" idea which is currently being analysed in more detail.

[envy887]

The latest paper on their in-air-capturing work seems to be from end november 2018:

https://elib.dlr.de/125921/

At the same conference, they also presented their view on the various RLV options (winged and non-winged):

https://elib.dlr.de/125063/

Thank you, this does seem to be the most recent paper.

From the second paper you linked, the same conclusion that I posted before is also clear: for the same engine technology and propellant, VTVL with downrange landing produces smaller vehicles than VTHL with either flyback or towback. The lowest dry mass vehicle is the staged combustion LH2 VTVL.

The VTVL design with gas generator engines is smaller than even the staged combustion VTHL design.

VTVL produces larger GLOMs, but lower dry masses. Since fuel is cheap and hardware (even reusable hardware) is expensive, the cost optima is to be to burn more fuel rather than build heavier hardware.