Stratolaunch: General Company and Development Updates and Discussions

[jongoff]

Even if unmanned the SL is still at risk, blow that up and they are out of business for a very long time.

Yeah, this is why you do things like blast protection around the engines so that a bad day on the rocket doesn't destroy the aircraft. While pilots might not feel comfortable on an aircraft being assisted by the mother of all JATO bottles (kids these days), ultimately the aircraft is more expensive than the pilots. You wouldn't want to take stupid risks with the aircraft any more than you would with the pilots on board. So take smart risks. :-)

The nice thing about pump-fed engines is that all the high energy bits are in a compact area that you can put blast shielding around (ala XCOR's approach to things). You don't need to protect in all directions (just in directions where shrapnel could hit the carrier vehicle or rocket), which makes it easier since you're really deflecting shrapnel and channeling it into safe directions. Also, since this is on the first stage the performance hit may not have to be that bad.

~Jon

[RanulfC]

It was/is a good idea. 

When they started they couldn't have seen how SpaceX was going to rewrite the pricing structure of the industry.  Plus SpaceX could gobble up much of the market with 4 launch pads and reusable rockets.

   It won't leave much for other players.

Actually that would be where SL has an advantage if they have a comparable payload to LEO with SpaceX F9R under a constellation scenario. SX has to wait till the pads are in position to launch a replacement satellite where as SL flies to the proper alignment and launches.

Randy

[notsorandom]

Just to put the final nail in the coffin of the X-15 analogy. The comparison to orbital launch is not a good one due to the drastic difference in the required performance. Air launch represents a very small performance improvement for an orbital system but a substantial boost for the X-15. The X-15 flew up to Mach 6 where LEO is equivalent to Mach 25. A drop from a high sub-sonic speed represents almost 1/6 of the total speed of the X-15 while only 1/25 of an orbital vehicle. Altitude is the other factor. A launch from 18km up is once again about a sixth of the X-15 maximum height yet a substantially smaller fraction of an orbital vehicle's height.

The rocket equation shows that it takes more propellant per velocity unit at the start of the burn than the end. The B-52 took off the most demanding sixth of the X-15 flight allowing it to be significantly smaller than if it had been launched from the ground. Air launching an orbital rocket also does this but for a much smaller portion of the delta V. Thus the drawbacks of air launch are much larger in proportion to the benefits.

[matthewkantar]

Pilots live are 'cheaper' than an aircraft? Maybe in strictly legal terms, but who thinks that way? Pilots for a carrier aircraft are an unnecessary anachronism at this point in time. Aside from whatever regulatory hurtles that would need clearing, I think pilots would be more of a liability than an asset to this program.

Matthew

[mr. mark]

Not sure if this article was posted but Stratolaunch will not be launching with Orbital or Dreamchaser.

"As recently as last fall, Beames spoke about a plan to put a human-crewed spacecraft developed by Sierra Nevada on the tip of the Orbital booster rocket.

But now that human spaceflight plan is shelved, along with Orbital’s planned rocket.

Beames said Orbital’s rocket “was not hitting the economic sweet spot to generate revenue,” so Vulcan has reopened the design plan and is “evaluating over 70 different launch vehicle variants.”
http://www.seattletimes.com/business/boeing-aerospace/space-wa2/

[simonbp]

Beames said Orbital’s rocket “was not hitting the economic sweet spot to generate revenue,” so Vulcan has reopened the design plan and is “evaluating over 70 different launch vehicle variants.”
http://www.seattletimes.com/business/boeing-aerospace/space-wa2/

It's almost like air launching a rocket with a very low payload per gross mass was terrifically inefficient. 

One day, Roc might be used to launch spacecraft, but right now it is a reincarnation of the Spruce Goose...

[Kabloona]

One day, Roc might be used to launch spacecraft, but right now it is a reincarnation of the Spruce Goose...

We should call it the Composite Dodo...currently flightless and soon to be extinct.

[edkyle99]

One day, Roc might be used to launch spacecraft, but right now it is a reincarnation of the Spruce Goose...

Not necessarily.  It should be the heaviest-lifting U.S. aircraft when completed.  There may be some utility in that capability.

 - Ed Kyle

[docmordrid]

True, but how many runways can handle it?

[Zed_Noir]

True, but how many runways can handle it?

Any runway that can handle a B-52. 

[adrianwyard]

With 6 engines and no payload we can guess at impressive takeoff performance! But with a payload/cargo pod of unknown mass and drag, who knows...

[Blackstar]

Air launch has always seemed like a terrible idea.

Tell that to Antonio Elias, a pretty brilliant guy who thought up Pegasus. It didn't "always seem like a terrible idea" to him, nor to Orbital or the many people who have done 40+ successful and profitable Pegasus launches.

Sure wings can help with that but at some point you get diminishing returns and if you throw that weight of wings and extra structure towards fuel instead, you might as well just go from the ground and have one less "stage". In my mind, the other obvious cons like no hold down testing and safety of carrying what equates to a giant pressure vessel quickly outweigh any pros.

After having defended Pegasus as a not-so-terrible idea, I do believe Antonio himself has conceded, IIRC, that the weight of the Pegasus wing more or less cancels out the performance gained by air launching, so it turns out to be a wash performance-wise. And you can't do hold-down tests anyway on solids, so that point is irrelevant for Pegasus.

Obviously scaling up the concept for Stratolaunch is different ball of wax, but it's inaccurate to make a blanket statement about all air launched systems being "terrible" ideas. If Pegasus was such a terrible idea it wouldn't still be flying.

I think I have posted either in this thread or elsewhere my notes from a talk that he gave early this year. He discussed their early assumptions for Pegasus, almost all of which proved wrong, and concluded that air launch makes little sense. I don't remember the specifics but you could simply do a search with my handle and his name and see if that pops up.

[Blackstar]

Allen is an extremely smart guy, but it just seems like he didn't do his due diligence here. Such a waste of potential 

I wrote an article a few years ago where I referred to this as "Egolauncher" and I still stick by that. I think Allen wanted the coolest rocket that any billionaire could get, better than the other billionaires' rockets, and the world's largest airplane to go along with it. That way when he hangs out with the other billionaires, he could brag about it. It's the same reason why billionaires buy big yachts and really expensive cars, so they can show them off.

And I think that only after he came up with the idea did he put the engineers to work to make it happen, and only after they started plugging away did the money people come in and start working out the numbers and discovered that the market won't support it.

To some extent this is how lots of business ideas happen: somebody comes up with a big idea, then tells people to go and make it work. Not everything starts with a market survey and focus groups. And of course they all could have initially said that this could make money and only after they started designing things did the numbers become clear and they realized that it's not going to be economical.

[Blackstar]

Air launch has always seemed like a terrible idea. The first issue is that while you get a bit of starting height, you are working with a negative vertical velocity that you have to overcome right from the get go after being dropped.

I was told by a person who was involved on the Air Force side that this was the problem with AirLaunch several years ago--that was supposed to be dropped out of the back of a C-17 cargo plane. One problem was that the downward velocity of the vehicle pretty much erased the benefits of the air launch. If I remember correctly, I think he said that it was the equivalent of launching it from a hole in the ground. (There were other drawbacks as well, such as the fact that no pilot in the Air Force would agree to fly with a huge tank of heated propane in his cargo hold.)

[PerW]

Sorry if it is a dumb question, but why is it negativ vertical speed? Why can't they start in the right direction?

[Patchouli]

Not sure if this article was posted but Stratolaunch will not be launching with Orbital or Dreamchaser.

"As recently as last fall, Beames spoke about a plan to put a human-crewed spacecraft developed by Sierra Nevada on the tip of the Orbital booster rocket.

But now that human spaceflight plan is shelved, along with Orbital’s planned rocket.

Beames said Orbital’s rocket “was not hitting the economic sweet spot to generate revenue,” so Vulcan has reopened the design plan and is “evaluating over 70 different launch vehicle variants.”
http://www.seattletimes.com/business/boeing-aerospace/space-wa2/

One reason for them reevaluating their LV might be the introduction of the BE-3 on the market.
A low cost fairly high thrust liquid hydrogen engine could drastically improve their payload maybe even bringing into the EELV class.

Of course there would be hydrogen handling issues but this probably is not a show stopper.

An interesting side effect of having on board hydrogen tanks the aircraft or maybe a later variant could be used as a test bed for testing hydrogen as a fuel for jet engines.

[Kabloona]

Sorry if it is a dumb question, but why is it negativ vertical speed? Why can't they start in the right direction?

It means when the rocket is released from the carrier aircraft, it starts falling, and usually there is a several second delay before ignition so the rocket can fall far enough away from the carrier aircraft not to damage the carrier aircraft in case of an explosion. So when the rocket ignites, it has been falling towards earth for several seconds and gaining "negative" vertical speed.

[meekGee]

Air launch has always seemed like a terrible idea.

Tell that to Antonio Elias, a pretty brilliant guy who thought up Pegasus. It didn't "always seem like a terrible idea" to him, nor to Orbital or the many people who have done 40+ successful and profitable Pegasus launches.

Sure wings can help with that but at some point you get diminishing returns and if you throw that weight of wings and extra structure towards fuel instead, you might as well just go from the ground and have one less "stage". In my mind, the other obvious cons like no hold down testing and safety of carrying what equates to a giant pressure vessel quickly outweigh any pros.

After having defended Pegasus as a not-so-terrible idea, I do believe Antonio himself has conceded, IIRC, that the weight of the Pegasus wing more or less cancels out the performance gained by air launching, so it turns out to be a wash performance-wise. And you can't do hold-down tests anyway on solids, so that point is irrelevant for Pegasus.

Obviously scaling up the concept for Stratolaunch is different ball of wax, but it's inaccurate to make a blanket statement about all air launched systems being "terrible" ideas. If Pegasus was such a terrible idea it wouldn't still be flying.

I think I have posted either in this thread or elsewhere my notes from a talk that he gave early this year. He discussed their early assumptions for Pegasus, almost all of which proved wrong, and concluded that air launch makes little sense. I don't remember the specifics but you could simply do a search with my handle and his name and see if that pops up.

Smart people are those that learn from experience and are able to change direction.  That's an honest and fair assessment, from someone who's been there, and so more power to him.

[Patchouli]

Sorry if it is a dumb question, but why is it negativ vertical speed? Why can't they start in the right direction?

It means when the rocket is released from the carrier aircraft, it starts falling, and usually there is a several second delay before ignition so the rocket can fall far enough away from the carrier aircraft not to damage the carrier aircraft in case of an explosion. So when the rocket ignites, it has been falling towards earth for several seconds and gaining "negative" vertical speed.

Still the benefits of starting higher up and the reduced atmospheric density greatly outweigh the loss of delta V from that.
Plus you still have the forward velocity from the aircraft which is still going to be much greater then the negative vertical element.
If the rocket is winged the sink rate is not going to be too great anyway.

[TrevorMonty]

Sorry if it is a dumb question, but why is it negativ vertical speed? Why can't they start in the right direction?

It means when the rocket is released from the carrier aircraft, it starts falling, and usually there is a several second delay before ignition so the rocket can fall far enough away from the carrier aircraft not to damage the carrier aircraft in case of an explosion. So when the rocket ignites, it has been falling towards earth for several seconds and gaining "negative" vertical speed.

Still the benefits of starting higher up and the reduced atmospheric density greatly outweigh the loss of delta V from that.
Plus you still have the forward velocity from the aircraft which is still going to be much greater then the negative vertical element.
If the rocket is winged the sink rate is not going to be too great anyway.

The slight benefits of extra height and speed at deployment are probably not worth developing a new vehicle/plane for.

The biggest benefit from air launch is having a choice of launch locations, not being locked to a latitude or longitude.