Big cryo rockets vs heterogenous systems to LEO

[pk67]

I would not like the discussion to focus on one of the stages of a multi-stage heterogeneous system. I am more interested in analyzing the potential gains resulting from the synergy of different systems.
For example, an optional stratospheric balloon stage could reduce air resistance and gravitational losses through a shorter take-off with higher acceleration, which translates into a lower take-off weight and an increase in the ratio of payload to take-off weight.
For example, I am interested in whether anyone published in recent years any advanced estimates and analyzes regarding the comparison of costs of delivering inertial mass to LEO from the Earth or from the Moon.

Modern missile systems, although advanced and proven in terms of reliability in terms of energy, are still very inefficient. Only a negligible percentage of the chemical energy of the fuel is converted into kinetic energy of the payload carried to the LEO.
Since the beginning of our civilization's efforts to conquer space, that is, for over 60 years, little has improved in this respect. Can we expect revolutionary changes in the next 30 or even 50 years or is it unlikely?
I am particularly interested in the predictions of people who consider themselves experts or are experts.

[Robotbeat]

It’s not negligible. A Falcon 9 is about 10% efficient at converting chemical energy to payload orbital energy (potential and kinetic). This is about comparable to a car hauling stuff up a hill and maybe even more efficient than an airplane used to haul stuff up a hill.

We can get more efficient by running stuff heavily oxidizer rich on the first stage, using near stoichiometric hydrolox on the upper stage, using full flow staged combustion, possibly even water injection assistance on the lift off of the first stage. Keep dry mass to an absolute minimum.

Might use a small velocity assist or a high altitude launch platform, but the inefficiencies of flight might negate these benefits.

But the cost of energy has little to do with the cost of space launch, with fuel costs being maybe 1% of overall costs. The real cost driver is building, integrating, and then throwing away aerospace quality hardware every launch. Reuse is how we reduce costs dramatically. Then we can worry about super high efficiency. (Possible to get about 25% efficient.)

The revolutionary changes are reuse, not efficiency. (Although you tend to improve efficiency when trying to get enough performance to enable fast and rapid & economical reuse.)

[Jim]

For example, an optional stratospheric balloon stage could reduce air resistance and gravitational losses through a shorter take-off with higher acceleration, which translates into a lower take-off weight and an increase in the ratio of payload to take-off weight.
For example, I am interested in whether anyone published in recent years any advanced estimates and analyzes regarding the comparison of costs of delivering inertial mass to LEO from the Earth or from the Moon.

Better efficiency does not translate to lower cost.   A balloon stage would only increase costs due to added complexity.

[sanman]

There more different things you have in there, the more things can go wrong.

[Robotbeat]

A Falcon 9 uses about 530 tonnes of propellant with a 2.36 O:F mix ratio, so about 157.8 tonnes of kerosene which has a specific energy of about 43GJ/tonne, so 6785GJ of fuel energy.

It gets about 22 tonnes to orbit expendably. So 308MJ per kilogram to orbit. The actual theoretical minimum, based on calculating the potential and kinetic energy of a stable orbit, is 32MJ/kg. So you can see that expendably it does slightly better than 10% efficient. With first stage reuse, it can only get about 16t to orbit, or about 424MJ/kg, slightly worse than 10% efficient.

Starship would be fully reusable and would have an efficiency of about 500MJ/kg to orbit, but that can be improved over time (earlier, more optimistic variants were to achieve about 300MJ/kg to orbit at least for propellant delivery).

[TrevorMonty]

JP aerospace are trying to fly airship to orbital  by low thrust. Concept has merit.

http://www.jpaerospace.com/

[Robotbeat]

JP aerospace are trying to fly airship to orbital  by low thrust. Concept has merit.

http://www.jpaerospace.com/

Unfortunately, it doesn’t.

[edzieba]

JP aerospace are trying to fly airship to orbital  by low thrust. Concept has merit.

http://www.jpaerospace.com/

Unfortunately, it doesn’t.

Nothing to fundamentally prevent it from working, it's basically the same technique as GOCE (and other thrust-augmented VLEO proposals) use, but expanding the orbital envelope lower and slower, with passage through the hypersonic regime only at extremely low atmospheric pressures - think of it as a waverider using a tensairity structure airframe rather than a rigid airframe, and the 'lighter than air' aspect as mostly a red herring. Its problem (as with gun-to-space concepts) is the economic case.

[pk67]

For example, an optional stratospheric balloon stage could reduce air resistance and gravitational losses through a shorter take-off with higher acceleration, which translates into a lower take-off weight and an increase in the ratio of payload to take-off weight.
For example, I am interested in whether anyone published in recent years any advanced estimates and analyzes regarding the comparison of costs of delivering inertial mass to LEO from the Earth or from the Moon.

Better efficiency does not translate to lower cost.   A balloon stage would only increase costs due to added complexity.

In this thread, I would like to analyze the possible synergies between different technologies. Of course, such a system is more complex than a system based on one key technology. However, many technologies can have dual or multiple uses. For this reason, these technologies will be developed regardless of whether they will be used to launch payloads into orbit. For example, if very large stratospheric balloons will be mass-produced for the tourism industry or also as a technology for military purposes for the economic protection of large cities against terrorist threats, e.g. drones, why not use such existing technology to reduce the energy balance needed to launch the payload into orbit?

[Robotbeat]

It helps to actually quantify the energy needs of achieving orbit so you don’t operate under false assumptions about where the costs lie.

[pk67]

A Falcon 9 uses about 530 tonnes of propellant with a 2.36 O:F mix ratio, so about 157.8 tonnes of kerosene which has a specific energy of about 43GJ/tonne, so 6785GJ of fuel energy.

It gets about 22 tonnes to orbit expendably. So 308MJ per kilogram to orbit. The actual theoretical minimum, based on calculating the potential and kinetic energy of a stable orbit, is 32MJ/kg. So you can see that expendably it does slightly better than 10% efficient. With first stage reuse, it can only get about 16t to orbit, or about 424MJ/kg, slightly worse than 10% efficient.

Starship would be fully reusable and would have an efficiency of about 500MJ/kg to orbit, but that can be improved over time (earlier, more optimistic variants were to achieve about 300MJ/kg to orbit at least for propellant delivery).

I apologize for not responding to every post and every argument raised.
I would just like to add for clarity that I assume full multiple use of all stages of the launching system. Perhaps it will be easier to conduct considerations if we divide our analyzes into three variants depending on the size of the market measured in tons of equivalent cargo, amounted to LEO?
a) 10k tonnes per year
b) 1M tons per year
c) 100M+ tonnes per year

This is my first suggestion, but maybe someone else has better suggestions?

[pk67]

It helps to actually quantify the energy needs of achieving orbit so you don’t operate under false assumptions about where the costs lie.

What false assumptions? Can you write a little clearer?
I assume that oil and natural gas will eventually run out and the extraction of what remains will be unprofitable. How to propel rocket stages in such circumstances?

I think that's a pretty reasonable assumption and the resulting question.

[Jim]

A Falcon 9 uses about 530 tonnes of propellant with a 2.36 O:F mix ratio, so about 157.8 tonnes of kerosene which has a specific energy of about 43GJ/tonne, so 6785GJ of fuel energy.

It gets about 22 tonnes to orbit expendably. So 308MJ per kilogram to orbit. The actual theoretical minimum, based on calculating the potential and kinetic energy of a stable orbit, is 32MJ/kg. So you can see that expendably it does slightly better than 10% efficient. With first stage reuse, it can only get about 16t to orbit, or about 424MJ/kg, slightly worse than 10% efficient.

Starship would be fully reusable and would have an efficiency of about 500MJ/kg to orbit, but that can be improved over time (earlier, more optimistic variants were to achieve about 300MJ/kg to orbit at least for propellant delivery).

I apologize for not responding to every post and every argument raised.
I would just like to add for clarity that I assume full multiple use of all stages of the launching system. Perhaps it will be easier to conduct considerations if we divide our analyzes into three variants depending on the size of the market measured in tons of equivalent cargo, amounted to LEO?
a) 10k tonnes per year
b) 1M tons per year
c) 100M+ tonnes per year

This is my first suggestion, but maybe someone else has better suggestions?

doesn't change anything

[Jim]

I assume that oil and natural gas will eventually run out and the extraction of what remains will be unprofitable. How to propel rocket stages in such circumstances?

Doesn't matter, there won't be any thing to launch or launch with when that happens.

[Jim]

For example, if very large stratospheric balloons will be mass-produced for the tourism industry or also as a technology for military purposes for the economic protection of large cities against terrorist threats, e.g. drones, why not use such existing technology to reduce the energy balance needed to launch the payload into orbit?

A.  That is not going to happen
b.  It still doesn't help.
c.  Reducing "energy balance" does mean reducing costs.
d.  What gas is going to be used for the balloons?  Helium is getting more expensive than propellants.

[Robotbeat]

It helps to actually quantify the energy needs of achieving orbit so you don’t operate under false assumptions about where the costs lie.

What false assumptions? Can you write a little clearer?
I assume that oil and natural gas will eventually run out and the extraction of what remains will be unprofitable. How to propel rocket stages in such circumstances?

I think that's a pretty reasonable assumption and the resulting question.

Even if you had to synthesize the hydrogen and methane using nuclear or solar electricity, it still wouldn’t significantly increase the cost of space launch, especially compared to where it is today.

Fuel costs are just so tiny you could multiply them by a factor of 10 with little effect.

[Robotbeat]

If we’re talking hypotheticals about really high launch rates, it’s possible to reduce costs with some sort of launch assist like a catapult or something. But it’s really tough to be launching often enough that it actually trades favorably vs the cost of propellant (even if we synthesize that propellant with electricity).

Balloons are almost certainly not the way to do it as they’re operationally complex, at best suited for a stunt. Typically the balloon itself would be expendable along with the helium used, and this would trade poorly over synthesized hydrolox or methalox.

Some sort of high altitude launch assist platform also probably wouldn’t be worth it.

Better to optimize the stage itself. A launch assist for the first 200m/s might be a little helpful if you’re launching multiple times per hour, but it’s not obvious even then.

[Vahe231991]

The proposed Long March 10, unlike the Long March 9, will use the non-cryogenic kerosene fuel for the first and second stages as well as its boosters, and only its third stage is to be fueled by liquid hydrogen, which is a cryogenic fuel.