Stratolaunch: General Company and Development Updates and Discussions

[Bubbinski]

Very good article Chris.  So the carrier plane is half done....wonder when it will be finished.  I'd sure like to see it fly. 

[a_langwich]

The field probably has to be close to the drop point, since it will have a hydro-lox upper stage. I don't think any air-drop rocket has ever had to deal with those kinds of cryogenic boil-off and top-off issues yet, right?

There is room for Stratolaunch to mount an overwing cryo storage pod to top off the upper stage. The tricky part of the whole operation is how quickly can the carrier aircraft (AKA Roc) climb to operational altitude carrying a large LV core with 2 solid motors.

Why bother, there is room in the fuselages.

Not too sure there is much room in those slim fuselages of the Roc for cryo storage and plumbing. More likely carrying jet fuel and some interesting arrangement for the 4 sets of big landing gears.

Overwing pod could gravity feed the the propellants to the Thunderbolt upper stage with external venting for broil-off. Avoid cryo stress on the Roc airframe. Also you would need set of cryo tanks, pumps & plumbing system in each fuselage to balance the Roc. Then there is the routing of the long cryo feed conduits through the wing structure.

Presuming additional cryo propellants aboard the Roc for broil-off replacement during the transit time to the launch location and altitude will be a large fraction of the upper stage propellant tankage total. Think the Roc will drop the Thunderbolt after several hours from take off. Large loaded air transports with big external payload generally don't accelerated or climb quickly.

Plus the pod could be jettison in event of emergencies.

Do they really need an _over_wing pod?  Seems like they could build up a center pod designed as a fairing between the rocket and the wing.  One benefit would be the opportunity for more mounting points for the rocket, less cantilevering.  (Better to move structure and reinforcement from the upper stages to the carrier aircraft, if you can.)  A second benefit would be a very short path from any cryogen tanking to the rocket.  A third would be that it fits roughly in the existing drag profile, so it would have less of a performance penalty.

Another thought is that you can do very aggressive, active cryocooling in the carrier aircraft, to minimize the size of tank needed.  I.e., the upper-stage vent on the rocket is part of a closed cooling loop, with the cooling done on the carrier.  When the rocket separates, the umbilical to the vent drops off, and the rocket vents to the atmosphere as usual.

[a_langwich]

So does the Stratolaunch review process reflect some problems meeting the performance requirements?  Were there showstoppers?  It seems unusual to have the carrier aircraft half built, while the rocket is still undergoing trades as to its basic composition.  Has the carrier aircraft performance been adjusted down due to compromises necessary during construction?

Would liquid engined lower stages (I know these aren't being considered right now, but...) be lighter but bulkier?  Is the concern that they wouldn't be enough lighter because of the horizontal-carry loading profile?

No offence to the Dream Chaser fans, but DC on Stratolauncher seems a far stretch.  Resized means a lot of redesign work, means even less cargo capability due to the structure necessary for wings and landing gear, etc.  Maybe suborbital has possibility, but I don't think Paul Allen really cares to be in that market--he had that opportunity ten years ago and passed on it.  It's great they are exploring every avenue, but in reality every direction that doesn't lead to "immediately available for sale" is probably not financially viable at this point.

Maybe they could interest XCOR in a lifting body fuselage for Lynx...

[Nindalf]

Resizing Dream Chaser makes sense for other launch possibilities than Stratolaunch, such as the fully-reusable version of Falcon 9.

Anyway, Dream Chaser on Stratolaunch gets mad style points.  Gorgeous combination.

[BrightLight]

Here's my article, using some of the good L2 info we had, with the media releases and a bit more L2 info.

http://www.nasaspaceflight.com/2014/10/dream-chaser-eyes-rides-with-under-review-stratolaunch-system/

The presence of an unexpected force......
The Rebel Alliance

[Nibb31]

It's pretty much established that StratoLaunch doesn't have much of an economical edge against other launch providers. It's just a very expensive reusable first stage.

The only real advantage of StratoLaunch is launch flexibility due to its capability to launch anywhere and potential quick response. As such, I suspect that the only potential customer willing to pay for those capabilities is the DoD.

Sticking DreamChaser on it means that they have to consider crew survivability for abort modes. What happens if the rocket doesn't start after being dropped? The drop needs to take place over an open area (desert or sea) while DreamChaser needs a runway nearby. Combining those two factors seriously limits StratoLaunch's "launch anywhere" advantage.

Similarly, if this DreamChaser can abort by popping a parachute and splashing down in the sea, there still needs to be a rescue force prepositioned nearby for every launch, just in case, which seriously limits StratoLaunch's "quick response" advantage and incurs a serious cost that doesn't make it suitable for low-cost tourist stunts or point-to-point travel.

[jeff.findley]

Sticking DreamChaser on it means that they have to consider crew survivability for abort modes. What happens if the rocket doesn't start after being dropped? The drop needs to take place over an open area (desert or sea) while DreamChaser needs a runway nearby. Combining those two factors seriously limits StratoLaunch's "launch anywhere" advantage.

I'd be concerned about possible violent failure modes of the solids.  These have happened infrequently with launch vehicles, but with some regularity.  Case rupture is a particularly nasty failure mode both in terms of the initial forces involved and in terms of large chunks of still burning debris.

[Rocket Science]

Sticking DreamChaser on it means that they have to consider crew survivability for abort modes. What happens if the rocket doesn't start after being dropped? The drop needs to take place over an open area (desert or sea) while DreamChaser needs a runway nearby. Combining those two factors seriously limits StratoLaunch's "launch anywhere" advantage.

I'd be concerned about possible violent failure modes of the solids.  These have happened infrequently with launch vehicles, but with some regularity.  Case rupture is a particularly nasty failure mode both in terms of the initial forces involved and in terms of large chunks of still burning debris.

True... But the beauty is that DC can fly away from debris and not have to descend though it potentially with chutes...

[JasonAW3]

Dumb question,

What would it take to get the full scale DreamChaser into orbit?  We are pretty sure Atlas and Deltas can do the job, but what other launcher, (US) are availible to put that bird into orbit?

[e of pi]

Dumb question,

What would it take to get the full scale DreamChaser into orbit?  We are pretty sure Atlas and Deltas can do the job, but what other launcher, (US) are availible to put that bird into orbit?

As I understand, it masses something in the 10-ton range, so it could also fit onto Falcon 9, but it's a bit out of reach for Antares (~6 tons) or anything smaller. The 75% version they're putting onto Birdzilla would have to be around 6 tons itself to fit that vehicle, so that would be potentially suitable for Antares, though again not for anything smaller.

[M129K]

Dumb question,

What would it take to get the full scale DreamChaser into orbit?  We are pretty sure Atlas and Deltas can do the job, but what other launcher, (US) are availible to put that bird into orbit?

At about 25000 lbs, it's within reach of Falcon 9. Aside from that, it might be doable with a hypothetical "Antares Heavy" but no other US vehicles come close to what's required.

Foreign launchers like Zenit, Ariane 5, H-2B and Proton are all capable enough as well.

[Lobo]

Dumb question,

What would it take to get the full scale DreamChaser into orbit?  We are pretty sure Atlas and Deltas can do the job, but what other launcher, (US) are availible to put that bird into orbit?

An upgraded Antares could do it...and it'd be owned by the same company as Pegasus II.  An upgraded Antares ironically could possibly have the same diameter solid motors launching it, just longer and heavier motors. 
I'm actually suprised they aren't investigating this, but then again, the deal is between SNC and Stratolaunch, not SNC and OrbATK.  OrbATK just happens to me making the LV Stratolaunch carries.

It is too bad that they probably can't up Stratolaunch/Pegasus II's performance along with trimming down DC enough so that it could carry the full size version.  Given they seem to be marketing it toward customer who would do LEO mission not to the ISS, but for other scientific purposes, the increased volume of the full sized DC would be beneficial. 

[butters]

So does the Stratolaunch review process reflect some problems meeting the performance requirements? 

It more likely reflects some problems with the economics of the dual RL-10 hydrolox upper stage. With that stage, it's hard to believe that Stratolaunch could be significantly cheaper than a higher-performing Atlas V! The business model is less implausible on paper without expensive cryogenic engines from Aerojet-Rocketdyne.

Five stage to orbit (including the carrier aircraft) is an... interesting solution.

[Lobo]

Good article.

Interesting that AJR got a stopwork order for the RL-10's for an upper stage.

In all fairness, it would seem an all solid LV would work the best with a carrier aircraft as there doesn't need to be any cryo considerations during the carrier flight.  Obviously LH2 is the most troublesome of that.
With solids, you just stack the stages horizontally at your hanger/launch facility like the KSC SLF, and then mate a Scaled DC to it and raise it up to the attachment coupling on Stratolaunch in the hanger.  DC's RCS system would need fueled propr to launch, but the nice thing there is that is non toxic propellants.  Would make processing pretty easy I think.  No need to be stacking big heavy solid motors on a pad.  It all could be done hoizontally in the hanger. 

For the two upper stages to replace a hydrolox one, I'd think probably a Castor 30XL topped with a Castor 30B perhaps?

Keroxide would work too.  (Hydrogen Peroxide and RP-1), as they wouldn't need any cryo handling by stratolaunch after take off or boiloff...and are non-toxic.  But that would require new booster and upper stage engines, liquid core and upper stage.  So the more readily available OrbATK solid motor options would be the likely better option there.

[MP99]

So does the Stratolaunch review process reflect some problems meeting the performance requirements? 

It more likely reflects some problems with the economics of the dual RL-10 hydrolox upper stage. With that stage, it's hard to believe that Stratolaunch could be significantly cheaper than a higher-performing Atlas V! The business model is less implausible on paper without expensive cryogenic engines from Aerojet-Rocketdyne.

Five stage to orbit (including the carrier aircraft) is an... interesting solution.

OK, don't shoot me!!!

If RL-10 is expensive, fit a pair of them where the current hybrid nozzles are. Put O2 tanks in place of both the solids and their oxidiser.

Fit an external tank (ET!) just for the H2, and discard it once in orbit.

Now, that's a proper "mini shuttle", and it brings the RL-10s back for refurb & reuse.

Just to make it clear - this is not serious. You'd have to use the RL-10s for LAS, among *many* other issues.

cheers, Martin

[M129K]

I wish you luck fitting enough LOX inside Dream Chaser for flying to LEO, as well as on orbit manoeuvring without engines.

[Zed_Noir]

...
If RL-10 is expensive, fit a pair of them where the current hybrid nozzles are. Put O2 tanks in place of both the solids and their oxidiser.

Fit an external tank (ET!) just for the H2, and discard it once in orbit.

Now, that's a proper "mini shuttle", and it brings the RL-10s back for refurb & reuse.

Just to make it clear - this is not serious. You'd have to use the RL-10s for LAS, among *many* other issues.

cheers, Martin

Think the RL-10s will be in an expandable upper stage between the DC and the lower two SRM stages. The LAS motors will be something else, most likely hypergolic. Of course there is the boil-off issue with cryogenic propellants.

[MP99]

I wish you luck fitting enough LOX inside Dream Chaser for flying to LEO, as well as on orbit manoeuvring without engines.

The LOX in a hydrolox upper stage is a relatively small proportion of the total volume.

On orbit manoeuvring would normally be via thrusters, I believe. At least, that's how I understood Dragon and Cygnus do it.

But, like I said, way too many problems to be practical.

Cheers, Martin

[Robotbeat]

X-37b originally needed to have 3.1km/s delta-v capability. Not TOO unreasonable to imagine a Modification of DC to take enough propellant for 3km/s. A good, but not heroic, glide forward liquid first stage (plus a little help from Stratolaunch) could be enough for DC to get to orbit (reentry from ~4km/s is much easier than 7km) if you already have 3km/s taken care of, especially since you can pick your launch site and get to launch at near-vacuum (the vac Isp for the MUCH denser methane/LOx is higher than the sea level Isp of Delta IV's hydrolox engines).

But can Stratolaunch and, say, Orbital Sciences afford it?

EDIT:As a side note, X-37b looks almost exactly the same as one of Shuttle's early flyback booster designs.

[RanulfC]

If RL-10 is expensive, fit a pair of them where the current hybrid nozzles are. Put O2 tanks in place of both the solids and their oxidiser.

Fit an external tank (ET!) just for the H2, and discard it once in orbit.

Now, that's a proper "mini shuttle", and it brings the RL-10s back for refurb & reuse.

Just to make it clear - this is not serious. You'd have to use the RL-10s for LAS, among *many* other issues.

1) I don't think the RL-10s would have enough T/W for this to work. IIRC the Air Launched Sortie Vehicle concept which was simlar but smaller and launched from the back of a 747 needed six RL-10s for the same job.

2) We're talking something like the MAKS here with the DC attached to a huge LH2 tank? http://en.wikipedia.org/wiki/MAKS_space_plane Also recall this is a "75%-Scale" DC as well...

3) Air Launch normally is supposed to have less requirement for a LAS at all, but I'd definatly want one for anything using solid boosters.

4) FOUR! (4!) Solid stages??!!?? Did no one learn anything from "Pegasus-1"? Obviously not...

5) Any hope of "economics" just goes out the window...

6) Kero-oxide idea sounds loads better than the solid idea. The only issue is finding a proper engine.. On the other hand of course there's one out there if you are willing to do the work (http://www.astronautix.com/engines/ba810.htm) I don't see that much difference in GLOW (485,000lbs versus 417,000 + the scale DC) and probably better performance all around. Tested and everything

7) There would be SOME room to move towards reusablity if they dropped the solids but I suspect that this is a basic issue with the winged lifting trajectory for the scheme. Solids are probably the only way to handle the stress' of the pull-up manuever with an "acceptable" mass ratio. I won't go over the various ways around that particular issue since there appears no interest in following up on any attempt to make this a "workable" concept...

Randy