Stratolaunch: General Company and Development Updates and Discussions

[envy887]

I am sure someone already asked it, but I wonder: can DreamChaser launch from Stratolaunch?

With what propulsion?

Edit: The Crew Dream Chaser is around 10 tonnes, while the largest rocket Stratolaunch is proposing has a LEO capacity of 6 tonnes. It would need a bigger rocket, or it won't reach orbit.

The Cargo Dream Chaser is even larger, at over 15 tonnes fully loaded.

[Jim]

I am sure someone already asked it, but I wonder: can DreamChaser launch from Stratolaunch?

Dream Chaser is spacecraft and not a launch vehicle

[su27k]

I am sure someone already asked it, but I wonder: can DreamChaser launch from Stratolaunch?

They considered it years ago, you can read the details here: https://www.nasaspaceflight.com/2014/11/snc-stratolaunch-dream-chaser-flights/

But no news recently, so the concept is probably abandoned.

[envy887]

I am sure someone already asked it, but I wonder: can DreamChaser launch from Stratolaunch?

They considered it years ago, you can read the details here: https://www.nasaspaceflight.com/2014/11/snc-stratolaunch-dream-chaser-flights/

But no news recently, so the concept is probably abandoned.

I'm not sure if that is at all practical, but it looks awesome.

[Archibald]

Well as said earlier Dreamchaser is too heavy so the plan was for a subscale, 75% shrunk variant. At least we got an awesome picture out of this: Roc + huge rocket + small lifting body.

[francesco nicoli]

I am sure someone already asked it, but I wonder: can DreamChaser launch from Stratolaunch?

They considered it years ago, you can read the details here: https://www.nasaspaceflight.com/2014/11/snc-stratolaunch-dream-chaser-flights/

But no news recently, so the concept is probably abandoned.

Thanks! I was thinking about that since it has been proposed to put a spaceplane on it..

[ThePhugoid]

<snip>
Just eyeballing the space plane it looks like it would need a booster stage or at least some additional fuel capacity, no?

In theory you can have wing tanks for kerosene during ascent.

It depends on how much of the airframe is tankage for propellants. Maybe X-15 style drop tanks if additional propellants is needed.

Doubt these are kerosene, given the scale of the vehicles plus the supposed goal of SSTO for the winged booster.  They are most likely hydrogen.

There are other options than kerosene and hydrogen, you might have heard of some upcoming rockets featuring methane. Methane does really seem to be the right choice (IMO) for a space plane.

Based on their payload mass targets, Hydrogen is the only option to get there.

[dwheeler]

Whatever the propellant combination, the huge issue with SSTO (and air launch makes too little a difference) is propellant mass fraction. Hydrolox: 92%, storable, methane, or kerosene + LOX = 95% or more.
<snip>

I guess that was my point. That layout doesn't look like it has anything close to those fractions. Again... just eyeballing it. It looks like you take the shuttle orbiter, double the length and use the cargo bay as fuel storage. That doesn't look like enough propellant to me. And that's with no SRBs. And the shuttle wasn't SSTO.

Excuse the crude Paint:

[Lars-J]

<snip>
Just eyeballing the space plane it looks like it would need a booster stage or at least some additional fuel capacity, no?

In theory you can have wing tanks for kerosene during ascent.

It depends on how much of the airframe is tankage for propellants. Maybe X-15 style drop tanks if additional propellants is needed.

Doubt these are kerosene, given the scale of the vehicles plus the supposed goal of SSTO for the winged booster.  They are most likely hydrogen.

There are other options than kerosene and hydrogen, you might have heard of some upcoming rockets featuring methane. Methane does really seem to be the right choice (IMO) for a space plane.

Based on their payload mass targets, Hydrogen is the only option to get there.

Based on what exactly? All the Hydrogen SSTO's out there? Making a hydrogen SSTO is not appreciatively easier than making a kerosene or methane SSTO. All have their pros and cons.

[ncb1397]

Whatever the propellant combination, the huge issue with SSTO (and air launch makes too little a difference) is propellant mass fraction. Hydrolox: 92%, storable, methane, or kerosene + LOX = 95% or more.
<snip>

I guess that was my point. That layout doesn't look like it has anything close to those fractions. Again... just eyeballing it. It looks like you take the shuttle orbiter, double the length and use the cargo bay as fuel storage. That doesn't look like enough propellant to me. And that's with no SRBs. And the shuttle wasn't SSTO.

Excuse the crude Paint:

Well, if you plug the shuttle's external tank and an empty orbiter into the rocket equation with SSME's vacuum isp, you do get about 9.5 km/s. Total weight would be a bit more than 3x SSME thrust so you have to add dry mass with more engines. And of course, that is with no payload. If it wasn't SSTO, it was pretty close.

Edit: with sea level isp, you get ~7800 m/s.

Edit: if you add in the OMS tanks and engines fueled and firing after Shuttle runs out of hydrolox, you get the following stats without staging the ET.

sea level SSME isp: 7970 m/s
vacuum SSME isp: 9650 m/s

So, it appears that that the real limiter for hydrolox SSTO is sea level isp. If you can get rid of the isp penalty, you got a much better shot. Stratolaunch is going up to 10 km in altitude, which means atmospheric pressure should be about 1/4 of sea level. That should help considerably.

[envy887]

<snip>
Just eyeballing the space plane it looks like it would need a booster stage or at least some additional fuel capacity, no?

In theory you can have wing tanks for kerosene during ascent.

It depends on how much of the airframe is tankage for propellants. Maybe X-15 style drop tanks if additional propellants is needed.

Doubt these are kerosene, given the scale of the vehicles plus the supposed goal of SSTO for the winged booster.  They are most likely hydrogen.

There are other options than kerosene and hydrogen, you might have heard of some upcoming rockets featuring methane. Methane does really seem to be the right choice (IMO) for a space plane.

Based on their payload mass targets, Hydrogen is the only option to get there.

Based on what exactly? All the Hydrogen SSTO's out there? Making a hydrogen SSTO is not appreciatively easier than making a kerosene or methane SSTO. All have their pros and cons.

It is easier if your starting mass is constrained. A better argument is that this isn't quite SSTO, so the starting mass constraint doesn't hurt a hydrocarbon vehicle as much.

[envy887]

Whatever the propellant combination, the huge issue with SSTO (and air launch makes too little a difference) is propellant mass fraction. Hydrolox: 92%, storable, methane, or kerosene + LOX = 95% or more.
<snip>

I guess that was my point. That layout doesn't look like it has anything close to those fractions. Again... just eyeballing it. It looks like you take the shuttle orbiter, double the length and use the cargo bay as fuel storage. That doesn't look like enough propellant to me. And that's with no SRBs. And the shuttle wasn't SSTO.

Excuse the crude Paint:

The Shuttle wasn't mostly lightweight propellant tanks, either. It had a heavy aluminum structure. This is probably a single composite skin or sandwich. And a lighter vehicle needs less TPS per pound.

[dwheeler]

Whatever the propellant combination, the huge issue with SSTO (and air launch makes too little a difference) is propellant mass fraction. Hydrolox: 92%, storable, methane, or kerosene + LOX = 95% or more.
<snip>

I guess that was my point. That layout doesn't look like it has anything close to those fractions. Again... just eyeballing it. It looks like you take the shuttle orbiter, double the length and use the cargo bay as fuel storage. That doesn't look like enough propellant to me. And that's with no SRBs. And the shuttle wasn't SSTO.

Excuse the crude Paint:

The Shuttle wasn't mostly lightweight propellant tanks, either. It had a heavy aluminum structure. This is probably a single composite skin or sandwich. And a lighter vehicle needs less TPS per pound.

Wouldn't this new vehicle have to be as strongly built as the shuttle orbiter or nearly so? I'm assuming it also lands horizontally.

[ThePhugoid]

<snip>
Just eyeballing the space plane it looks like it would need a booster stage or at least some additional fuel capacity, no?

In theory you can have wing tanks for kerosene during ascent.

It depends on how much of the airframe is tankage for propellants. Maybe X-15 style drop tanks if additional propellants is needed.

Doubt these are kerosene, given the scale of the vehicles plus the supposed goal of SSTO for the winged booster.  They are most likely hydrogen.

There are other options than kerosene and hydrogen, you might have heard of some upcoming rockets featuring methane. Methane does really seem to be the right choice (IMO) for a space plane.

Based on their payload mass targets, Hydrogen is the only option to get there.

Based on what exactly? All the Hydrogen SSTO's out there? Making a hydrogen SSTO is not appreciatively easier than making a kerosene or methane SSTO. All have their pros and cons.

No, based on physics.  The ability to succeed with SSTO means pulling out all the stops in every performance parameter you can within the design in both mass fraction as well as propulsion.  You have to do the crazy efficient propellant mass fraction no matter the propellant choice, but with hydrogen you can get an extra 30% in specific impulse over methane.  This fact, combined with their aggressive payload targets on both the cargo launchers as well as the SSTO spaceplane, leads me to assume hydrogen.

[GWH]

So anyone think they will try to go SSTO right from the get go? 2 stage really doesn't make much sense as a development path to  the space plane.

The image of the tri-core pretty clearly looks like a multi-stage rocket,  the lines on the single core are hard to make out.

[Lars-J]

Based on their payload mass targets, Hydrogen is the only option to get there.

Based on what exactly? All the Hydrogen SSTO's out there? Making a hydrogen SSTO is not appreciatively easier than making a kerosene or methane SSTO. All have their pros and cons.

No, based on physics.  The ability to succeed with SSTO means pulling out all the stops in every performance parameter you can within the design in both mass fraction as well as propulsion.  You have to do the crazy efficient propellant mass fraction no matter the propellant choice, but with hydrogen you can get an extra 30% in specific impulse over methane.  This fact, combined with their aggressive payload targets on both the cargo launchers as well as the SSTO spaceplane, leads me to assume hydrogen.

Don't stare yourself blind on specific impulse, an entire industry did that for decades without making any progress towards reusable vehicles, never mind SSTOs. And you are only going to LEO, where Isp matters the least. Keep in mind that a Atlas V (without SRBs) has a slightly worse payload fraction than an all-kerolox F9 (expendable) to LEO, despite having a hydrogen upper stage with an engine with much better Isp. There are more factors at play.

[QuantumG]

Air launch has a primary design limitation that favours dense propellants.

[ncb1397]

Based on their payload mass targets, Hydrogen is the only option to get there.

Based on what exactly? All the Hydrogen SSTO's out there? Making a hydrogen SSTO is not appreciatively easier than making a kerosene or methane SSTO. All have their pros and cons.

No, based on physics.  The ability to succeed with SSTO means pulling out all the stops in every performance parameter you can within the design in both mass fraction as well as propulsion.  You have to do the crazy efficient propellant mass fraction no matter the propellant choice, but with hydrogen you can get an extra 30% in specific impulse over methane.  This fact, combined with their aggressive payload targets on both the cargo launchers as well as the SSTO spaceplane, leads me to assume hydrogen.

Don't stare yourself blind on specific impulse, an entire industry did that for decades without making any progress towards reusable vehicles, never mind SSTOs. And you are only going to LEO, where Isp matters the least. Keep in mind that a Atlas V (without SRBs) has a slightly worse payload fraction than an all-kerolox F9 (expendable) to LEO, despite having a hydrogen upper stage with an engine with much better Isp. There are more factors at play.

If comparing multistage to SSTO, it would be better to pick some other orbit than LEO because SSTO is going to have to provide ~9 km/s which is more akin to escape injections on multistage rockets. A TSTO stage to LEO only has to provide half that per stage. It would be better to use some high energy orbit like C3=10 km2/s2. In which case, the mass fractions are the following

Delta IV Heavy
mass:733,000 kg
payload: 8,460 kg
fraction: 1.15%

Falcon Heavy
mass: 1,420,000 kg
payload: 12,345 kg
fraction: .869%

[Lars-J]

Based on their payload mass targets, Hydrogen is the only option to get there.

Based on what exactly? All the Hydrogen SSTO's out there? Making a hydrogen SSTO is not appreciatively easier than making a kerosene or methane SSTO. All have their pros and cons.

No, based on physics.  The ability to succeed with SSTO means pulling out all the stops in every performance parameter you can within the design in both mass fraction as well as propulsion.  You have to do the crazy efficient propellant mass fraction no matter the propellant choice, but with hydrogen you can get an extra 30% in specific impulse over methane.  This fact, combined with their aggressive payload targets on both the cargo launchers as well as the SSTO spaceplane, leads me to assume hydrogen.

Don't stare yourself blind on specific impulse, an entire industry did that for decades without making any progress towards reusable vehicles, never mind SSTOs. And you are only going to LEO, where Isp matters the least. Keep in mind that a Atlas V (without SRBs) has a slightly worse payload fraction than an all-kerolox F9 (expendable) to LEO, despite having a hydrogen upper stage with an engine with much better Isp. There are more factors at play.

If comparing multistage to SSTO, it would be better to pick some other orbit than LEO because SSTO is going to have to provide ~9 km/s which is more akin to escape injections on multistage rockets. A TSTO stage to LEO only has to provide half that per stage. It would be better to use some high energy orbit like C3=10 km2/s2. In which case, the mass fractions are the following

Delta IV Heavy
mass:733,000 kg
payload: 9,285 kg
fraction: 1.26%

Falcon Heavy
mass: 1,420,000 kg
payload: 13,615 kg
fraction: .958%

Sigh. This is about is best for LEO delivery, since that is what “Black Ice” would go to. Or do you really think Stratolaunch is targeting C3=10 km2/s2 with this planned space plane? LEO is a relatively low energy target compared to that, so Hydrogen suffers.

[QuantumG]

I gotta tell ya, it'll be a big upset if Stratolaunch get full reusability first.

It'll be Rutan's revenge.