Stratolaunch: General Company and Development Updates and Discussions

[speedevil]

They have chosen to go with Methalox, rather than Kerolox, for various reasons, including that Mars works better with it,

Weird that. Given Musks endgame has always been Mars, and Mars has no oil to make RP1 out of.

Your initial claim had nothing whatsoever to do with Mars.
You were claiming that complete reusability was impossible with kerolox.
To restate.

If you swap the Raptor engines with Merlin engines, for BFS, and keep the figures otherwise the same, it gets 50 tons to orbit wholly reusably and can recover both stages with no operational changes.

This is off-topic, discussion of stratolaunchs options and possible performance is interesting - but spacex's claims (which arguably do not exist) on reusability of kerolox aren't.

[john smith 19]

{emphasis mine}  Do you have a source for that?? 

To my knowledge no-one has built and tested an air-breathing hydrolox engine yet.

I can give you a figure for thrust specific fuel consumption of 0.937 Kg/N Hr.

You're a bit behind the times.

https://history.nasa.gov/SP-4404/ch8-10.htm

[speedevil]

{emphasis mine}  Do you have a source for that?? 

To my knowledge no-one has built and tested an air-breathing hydrolox engine yet.

I can give you a figure for thrust specific fuel consumption of 0.937 Kg/N Hr.

You're a bit behind the times.

https://history.nasa.gov/SP-4404/ch8-10.htm

For an engine with a subsonic intake, at sea level, static.
Plus, the Germans did it twenty years earlier.

(and both are as utterly irrelevant to a supersonic airbreathing vehicle as the Aeolipile.)

Airbreathing supersonic hydrogen engines are rather scarce unfortunately.

[john smith 19]

For an engine with a subsonic intake, at sea level, static.
Plus, the Germans did it twenty years earlier.

(and both are as utterly irrelevant to a supersonic airbreathing vehicle as the Aeolipile.)

Airbreathing supersonic hydrogen engines are rather scarce unfortunately.

He asked a question and I answered it. 

BTW I presume the engine you're thinking about was the test one Hans van Ohain had built for a test project. AFAIK it was basically a proof of concept, never expected to fly.

The engine I ref'd was the one designed to run the CL400 Suntan reconnaissance aircraft, who's target speed was M2.5.  A project that spent $250m by the time it was cancelled. IOW A pretty serious effort.

NACA/NASA seems to have run a number of test bed projects to investigate H2 for ramjets, turbojets and in the 70's turbofans for passenger jets.  If you can turn it into a gas it burns fast and you can use smaller size combustors. IOW no show stoppers.

[Elmar Moelzer]

Check Musk's appearance at MIT in 2014.

That was a long time ago. He had changed his mind again since then. Then changed his mind again, when they prioritized BFR/BFS.

Are you saying RP1 is exceptional, or could it be any hydrocarbon that can give a good mass fraction?

No, all I meant to say was that we were able to observe good mass fractions with RP1 on partially reusable rockets and the mass fraction of the F9 US is even better than on the first stage.

You don't seem to think anyone is developing a spaceplane. BFS is a spaceplane and SX are developing. So you are wrong. You're right it won't be easy.

I said "that spaceplane". Context matters. I was talking about the one to be developed by Stratolaunch.

I keep hearing that but have you noticed the size of the figure Musk includes in the pictures? It's tiny.
You can call them "control surfaces" but I don't expect they will be getting any smaller. I suspect they will get bigger but we'll see.

That is to be seen.

Stratolaunch is not part of Virgin Galactic. It is a subsidiary of Paul Allan's company "Vulcan."

Yeah, I don't know what got into me there. I meant Stratolaunch, of course.

[john smith 19]

That was a long time ago. He had changed his mind again since then. Then changed his mind again, when they prioritized BFR/BFS.

I'll take your word for that. I don't follow his Twitter feed. That suggests SX is doing a lot more science than engineering than people realize if their views on what's viable keep flip flopping.

No, all I meant to say was that we were able to observe good mass fractions with RP1 on partially reusable rockets and the mass fraction of the F9 US is even better than on the first stage.

Unfortunately it turns out that even with those mass fractions SX were still unable to achieve US recovery with an economically viable payload on board. It's no good being able to do it if you cut the usable payload from >22 tonnes down to 10 say.

I said "that spaceplane". Context matters. I was talking about the one to be developed by Stratolaunch.

Noted.  If Pegasus is the planned vehicle it would be good to get a few launches using it out the way first.

That is to be seen.

True. I await this years IAC meeting with interest. But OT for this thread

Yeah, I don't know what got into me there. I meant Stratolaunch, of course.

TBH this is the other startup with a big plan as "Stage 0" (although AFAIK Orbital's Pegasus is still open for business, which makes three). There just seem to be so many  startups at the moment that it's hard to keep track of them.
One thing I noticed. VG's launch aircraft seems to have have had a regular business being hired out to others for various drop tests. I don't know if they've made much doing it but at least it's kept the flight crew in practice. I wonder if Stratolaunch will do likewise?

[Elmar Moelzer]

Unfortunately it turns out that even with those mass fractions SX were still unable to achieve US recovery with an economically viable payload on board. It's no good being able to do it if you cut the usable payload from >22 tonnes down to 10 say.

Reusable upper stages are hard, no matter what propellant combination you use. The thing with Musk is that he is always willing to change his mind on anything. He initially wanted to reuse the upper stage. Then it looked like they would not be able to do it. Or rather, it would have reduced payloads to GTO, their bread and butter, too much and for just LEO, they were not sure it would be worth it. Then they were able to update F9 performance quite significantly and it looked like iUS reuse would make sense for F9 and most definitely for FH. But then they decided to go straight to BFS/BFR instead, which changes everything anyway.
And quite frankly, it is a good thing that they are willing to change their minds that quickly and that often.
The "we thought about it 40 years ago and decided it can't be done" mentality was one reason why there was little progress in space launch until SpaceX came along.

[speedevil]

Unfortunately it turns out that even with those mass fractions SX were still unable to achieve US recovery with an economically viable payload on board. It's no good being able to do it if you cut the usable payload from >22 tonnes down to 10 say.

Nobody cares.
747-400 penalty is in the range of 15%. (remove gear, reversing hardware, lighten structure so it doesn't need to take more than one flight, land on foamed runway)
Stratolaunch probably similar if they throw away the carrier.

BFS payload if you remove all of the reusable features in the range of two thirds.
Falcon heavy penalty (partially reusable admittedly) is in the range of two thirds.

Shuttle penalty of being reusable is in the range of three quarters. (skeleton payload fairing and OMS/engine attached in place of shuttle.

Nobody cares about the payload your vehicle could have achieved if it was not reusable, they care about how much it costs to get their payload to orbit when they need it.

Whatever stratolaunch ends up doing, that's the important bit, not the specific manner that they achieve its technical merits.

[Comga]

Every thread does not have to be about SpaceX

This one is about Stratolaunch

A reason for this enormous aircraft still has not been made pubic.
Perhaps it will
Until then it is possible to post a guess not yet posted.
(I like some attributed to Jon Goff.)
But it isn’t worthwhile.

[WmThomas]

Every thread does not have to be about SpaceX

--Start grammar snark--

Your sentence means "No thread has to be about SpaceX."

That is true. No thread has to to exist at all or be about anything.

But I like it that some threads are about SpaceX.

I guess you meant to say "Not every thread has to be about SpaceX."  Which means that some threads should be about non-SpaceX topics.

I like it that some threads are not about SpaceX.

--End grammar snark--

[Lar]

When snarking grammar please remember that not all of us speak English as a first language. Which is too bad because I like snarking grammar too. but it's not fair in all cases.

Edit:
That may have been a little too subtle. Don't nitpick grammar unless you are
1) already friends with the person you're picking AND
2) in the party thread

thank you.

[john smith 19]

But then they decided to go straight to BFS/BFR instead, which changes everything anyway.

True.

And quite frankly, it is a good thing that they are willing to change their minds that quickly and that often.

Also true.

The "we thought about it 40 years ago and decided it can't be done" mentality was one reason why there was little progress in space launch until SpaceX came along.

Also true. This industry has a lot of "folklore." 
My personal favorites are "Expendable rocket engines can't be reused," despite the fact that only solids are not test fired.
The other one is the ongoing refusal to do LOX cooling, despite it being SOP for both NTO and HTP oxidizer engines. Both are also aggressive oxidizers but LOX is y'know special. 
So any time you want to change fuels you have to reconsider the amount you need for cooling, which has nothing to do with how much you need to inject into the chamber.

[john smith 19]

Nobody cares.
747-400 penalty is in the range of 15%. (remove gear, reversing hardware, lighten structure so it doesn't need to take more than one flight, land on foamed runway)
Stratolaunch probably similar if they throw away the carrier.

BFS payload if you remove all of the reusable features in the range of two thirds.
Falcon heavy penalty (partially reusable admittedly) is in the range of two thirds.
....
Nobody cares about the payload your vehicle could have achieved if it was not reusable, they care about how much it costs to get their payload to orbit when they need it.

They do when you start from an expendable LV, try and turn it into an RLV with available materials to hand and find it's payload has shrunk so much it's no longer economically viable. 

"Fully reusable" == fully economically reusable, otherwise it's a technical tour de force but practically unusable.

Whatever stratolaunch ends up doing, that's the important bit, not the specific manner that they achieve its technical merits.

Then we are in violent agreement.  , although technically the "important bit" is they offer the service at a price affordable to their potential customers.

[Rocket Science]

As I posted in the "DC Update" thread of what might have been or will be... Who knows? Enjoy!

[Archibald]

Oh my GOSH !! This video is insanely awesome. It has some kind of Moonraker vibe. Plus the Valkyries as background. Wunderbar !

Who did that ?

No kidding: first time I saw it, I briefly thought both Dreamchaser and Stratolaunch had been painted in Air Force One colors (white and blue) and it was a kind of joke "President Trump new space presidential plane"

[Comga]

Oh my GOSH !! This video is insanely awesome. It has some kind of Moonraker vibe. Plus the Valkyries as background. Wunderbar !

Who did that ?

No kidding: first time I saw it, I briefly thought both Dreamchaser and Stratolaunch had been painted in Air Force One colors (white and blue) and it was a kind of joke "President Trump new space presidential plane"

First time through your post looked serious.  We need bigger eye-winking emoticons.
It's not easy to make a combination of super-plane, rocket, winged spacecraft, and the ISS appear boring.
But they did it.

[Robotbeat]

I think it's cool. But it's missing wind turbines on the hills.

[Lars-J]

Stratolaunch on Mars? (My first reaction)

[Archibald]

Oh my GOSH !! This video is insanely awesome. It has some kind of Moonraker vibe. Plus the Valkyries as background. Wunderbar !

Who did that ?

No kidding: first time I saw it, I briefly thought both Dreamchaser and Stratolaunch had been painted in Air Force One colors (white and blue) and it was a kind of joke "President Trump new space presidential plane"

First time through your post looked serious.  We need bigger eye-winking emoticons.
It's not easy to make a combination of super-plane, rocket, winged spacecraft, and the ISS appear boring.
But they did it.

I don't understand a single word about your answer. What are you trying to say ?

[Rocket Surgeon]

I don't know if this has been posted yet, but here is something interesting I found on LinkedIn while looking for jobs in 'Aerospace Structures". It's a posting for a 'Staff Structural Engineer'. No link to the Stratolaunch website, so I'm suspicious, but the description definitely matches the company.
https://goo.gl/wE1KLb

But this is the interesting part. "As a Staff Structural Engineer, you will be responsible for leading the structural development of a launch vehicle and its pylon"

I wonder what it means by 'Pylon' and if more need to be constructed.