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GW Johnson

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From: McGregor, Texas USA

Registered: 2011-12-04

Posts: 5,593

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Re: Spin Launch SpinLaunch Vacuum Launches Centrifuge Launched Mass

The photo in post 75 shows the spin launch carrier vehicle,  a streamlined dart.  The side of it opens up laterally like a clamshell,  to release the payload and its booster rocket.  The clamshell closes and the dart falls back,  finally slowed by a chute,  for a landing near the launch site.

This kind of trajectory apogees in altitude (zero vertical velocity) with virtually-zero horizontal velocity.  The payload's booster rocket has to take it from essentially zero speed to orbital speed,  horizontally,  in the desired direction.  Since it is above the sensible atmosphere,  and radius from the Earth's center is not changing during the burn,  there are no gravity and drag losses to cover. Circular orbit speed up there is about 7.7-something to 7.8 km/s.  A transfer ellipse from that point instead of just circularizing,  has a higher velocity requirement.

In essence,  the unpowered carrier dart has as its payload the actual payload,  plus a booster rocket capable of delivering 7.8 km/s dV or more,  while carrying that actual payload.  That booster rocket will be quite a bit bigger than the actual payload.  The rocket equation demands that. 

Acceptable payload fractions and the booster stage Isp's determine how many stages are required.  Bear in mind that to withstand 5000-10,000 gees laterally,  the inert fractions for the booster stages are going to be much higher than you are used to seeing!  Strength always costs more mass.  It is inevitable.

While I hope they succeed,  it is my opinion that the considerations I just described render the potential of this launch technique to be quite limited.

GW

Last edited by GW Johnson (2024-06-30 12:11:38)

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GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

SpaceNut

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From: New Hampshire

Registered: 2004-07-22

Posts: 29,257

Re: Spin Launch SpinLaunch Vacuum Launches Centrifuge Launched Mass

https://www.spinlaunch.com/orbital

shows that its tipped

tahanson43206

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Registered: 2018-04-27

Posts: 17,979

Re: Spin Launch SpinLaunch Vacuum Launches Centrifuge Launched Mass

In looking at the video SpaceNut found, at 2:40 minutes... we see that the rockets are liquid, not solid.

(th)

GW Johnson

Member

From: McGregor, Texas USA

Registered: 2011-12-04

Posts: 5,593

Website

Re: Spin Launch SpinLaunch Vacuum Launches Centrifuge Launched Mass

Solid or liquid,  the components must be supported and stressed for centrifugal gee in the 10,000 gee class.  It appears with the angled launch,  they do not intend to recover and re-use the carrier vehicle.  BTW,  its pointed nose will be blunted by air friction heating on the way up.  Sharp points do not stay sharp in hypersonic flow. 

GW

PS -- that last sentence is also why I do not believe you can build an air inlet for high hypersonic flight in the atmosphere,  or for flying into space with airbreathing propulsion.  If the sharpness goes away,  so does the inlet pressure recovery,  and its mass ingestion characteristics.  Its drag also goes up;  a lot! 

Not to mention that thrust is a factor times ambient air pressure,  with any imaginable type of airbreathing jet engine.  10 times nothing is still nothing,  no matter which way you try to "spin" the situation.  No thrust is simply no climb rate and/or pathwise acceleration.  Isp doesn't matter once that obtains.

Last edited by GW Johnson (Yesterday 16:08:16)

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GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

tahanson43206

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Registered: 2018-04-27

Posts: 17,979

Re: Spin Launch SpinLaunch Vacuum Launches Centrifuge Launched Mass

For GW Johnson re #79 and topic in general...

I plead guilty to having led this discussion astray due to the incorrect assumption the SpinLaunch rocket package would use solid fuel rockets.  My incorrect assumption was based in large part on the plans of Dr. John Hunter for his massive gas gun, which would have been able to use solid fuel because the acceleration planned for that system was along the center line of the projectile.

Having acknowledged that the SpinLaunch system appears to be intended to use liquid propellants, please assess the potential of hypergolic propellants to achieve LEO, given the lean-to-the-East inclination of the proposed SpinLaunch orbital system.

We can hopefully assume that the pointed nose of the projectile will survive to fly again, but if it becomes rounded as you predict, that component can be replaced at the maintenance facility. 

This discussion is not about air breathing engines of any kind, although I recognize that discussion of air breathing engines is going on in other topics.

Please assess the potential of hypergolic fuels to complete the SpinLaunch orbital mission.

(th)

SpaceNut

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From: New Hampshire

Registered: 2004-07-22

Posts: 29,257

Re: Spin Launch SpinLaunch Vacuum Launches Centrifuge Launched Mass

The flight path at first will be faster along a similar route but where the stage for the payload takes over is about in the same location as the falcon 9 profile. From when the second stage is no more, and we are using the kick stage.

The kinetic energy once launched will exit the system but begin to slow as it climbs with drag decreasing as it rises.

tahanson43206

Moderator

Registered: 2018-04-27

Posts: 17,979

Re: Spin Launch SpinLaunch Vacuum Launches Centrifuge Launched Mass

For SpaceNut re #81 ... thanks for this interesting and helpful flight profile!

Here is a preliminary assessment by ChatGPT regarding the revised understanding of the SpinLaunch orbital concept, as revealed by the video you found:

Hello Again... I'd like to enlist your assistance in thinking through the implications of a clarification our little group received regarding the SpinLaunch orbital configuration. We have learned (a) that the toss will be inclined to the East, which means that the payload package will have some momentum toward the East, and (b) the second and third stage rockets will be liquid instead of solid fueled. We presume the fuel for these stages will be hypergolic. We can see in the company video that the fuel containers are spherical, which would imply that the G forces will be distributed against the outside wall of the spheres during spinup before launch. As you evaluate this scenario, I'm wondering if you can predict if hypergolic fuels can survive 10,000 G's and then perform their thrust mission after the outer casing reaches apogee. We have learned that the outer casing is to open like a clamshell and release the payload and two stages above the sensible atmosphere.

Key Points to Consider

1. Inclined Launch and Eastward Momentum:
- The payload package will have an initial momentum toward the east due to the inclined launch.
- This eastward momentum will aid in achieving an orbital trajectory, leveraging Earth's rotation.

2. Liquid-Fueled Second and Third Stages:
- The second and third stages will use liquid fuel, likely hypergolic, which ignites spontaneously upon contact with an oxidizer.
- These stages will be contained in spherical fuel containers during spinup.

3. 10,000 G Forces on Hypergolic Fuels:
- The spherical fuel containers will experience immense G forces during spinup, which will press the fuel against the outer walls of the spheres.
- After reaching apogee, the outer casing will open like a clamshell, releasing the payload and stages.

Evaluating Hypergolic Fuels under 10,000 G's

Physical Properties of Hypergolic Fuels:
- Density and Viscosity: These fuels are relatively dense liquids with moderate viscosity.
- Phase Stability: Hypergolic fuels remain stable in liquid form over a range of temperatures and pressures.

Effects of High G Forces:
1. Fuel Distribution:
   - The centrifugal forces will cause the fuel to be evenly distributed against the inner walls of the spherical containers.
   - This distribution should not affect the chemical stability of the fuel, provided the containers are designed to withstand such forces.

2. Structural Integrity:
   - The spherical design is advantageous as it uniformly distributes stress, minimizing the risk of structural failure.
   - High G forces may induce minor physical changes, such as increased pressure at the fuel-container interface, but these are typically within the design tolerances of aerospace-grade materials.

3. Ignition and Combustion:
   - Upon release from the clamshell, the reduced G forces will allow the fuel to flow toward the combustion chamber.
   - Hypergolic fuels are known for their reliable ignition characteristics, which should remain unaffected by prior exposure to high G forces, provided no phase change (e.g., vaporization) occurs.

Predicted Performance After Release

1. Clamshell Release:
- The outer casing opening like a clamshell at apogee will subject the payload to a momentary period of microgravity.
- This should allow the fuel to settle naturally within the feed systems of the second and third stages.

2. Thrust Performance:
- The spontaneous ignition property of hypergolic fuels ensures reliable engine start once the fuels come into contact with each other.
- The pre-launch high G forces should not impair the performance, as the fuels are designed to operate under varying conditions in space.

3. Structural Considerations:
- Ensure that fuel lines and tanks are designed to withstand both the spinup G forces and the subsequent microgravity environment.
- Pay particular attention to the material compatibility and structural integrity under both extreme acceleration and space conditions.

Conclusion

Hypergolic fuels should be capable of surviving the 10,000 G forces during the spinup phase, given that their physical and chemical stability is maintained, and the containers are designed to handle such stresses. Upon release at apogee, the transition to a microgravity environment should allow for normal fuel flow and combustion, ensuring the stages can perform their thrust mission as intended.

If you have any specific concerns or further details you'd like to discuss, feel free to let me know!

(th)

tahanson43206

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Registered: 2018-04-27

Posts: 17,979

Re: Spin Launch SpinLaunch Vacuum Launches Centrifuge Launched Mass

As an update ... In a Google lookup I ran today, it appears that the orbital vehicle is intended to put up to 200 kg in orbit as the payload.  This means the mass of the vehicle itself will be considerably greater.

For GW Johnson ... is the spreadsheet capable of dealing with a three stage rocket such as this, with the unusual circumstance of the first stage consuming no fuel?  I would think the rocket equation would have a hard time with this.

Would it make more sense to model a two stage rocket that is already in motion?

If you ignite the second stage while the vehicle still has momentum heading up and East, then the transition would be similar to a traditional rocket after the first stage separates.

(th)

GW Johnson

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From: McGregor, Texas USA

Registered: 2011-12-04

Posts: 5,593

Website

Re: Spin Launch SpinLaunch Vacuum Launches Centrifuge Launched Mass

Rocket equation analysis makes ABSOLUTELY NO sense for the "first stage",  that being where the carrier ends up launching whatever it contains.  There would be speed,  altitude,  and path angle data for that point,  and I have NEVER seen any credible data,  not yet.

From that point,  you could do rocket equation analyses of however many stages the rocket has,  that pushes the actual payload into orbit from there.  But you have to make some educated guesses for what the gravity and drag losses might be.  And they would be only guesses.

GW

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GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

tahanson43206

Moderator

Registered: 2018-04-27

Posts: 17,979

Re: Spin Launch SpinLaunch Vacuum Launches Centrifuge Launched Mass

For GW Johnson re #84

Thanks for engaging with me on this important topic...

It ** sounds ** as though you think the spreadsheets can deal with the "missing" first stage.

Let's assume the package departs the launcher at 5000 mph and follows a 45 degrees angle toward the East, and let us suppose the apogee of the parabola is at 100,000 feet. 

Let's also accept the reported satellite payload as 200 kg.

Can the spreadsheet compute the components in the package, by working backward from the result (200 kg in orbit) to the end of the first stage boost?

You don't need to be reminded, but for our readers who do not follow topics as closely as members, we are pursuing this option to see if it might provide a competitive cost for the McGregor Space Systems Orbiting Fuel Depot. (MSSOFD).

Working backward:
5) 200 kg satellite in orbit
4) Third stage hypergolic rocket boost
3) Second stage hypergolic rocket boost
2) First stage fling by SpinLaunch arm
1) Entire package is secured to SpinLaunch arm at rest.

The goal of the exercise is to confirm that substituting electric current for the first stage for the traditional solid or liquid fuel rocket stage will result in cost savings for the customer.

The company goal of launching every hour means that there will be 24 different planes in work. That would presumably be advantageous to customers, who can launch to meet the refueling depot in one of those 24 planes.

(th)