Vertical Launch Assist Technologies for SSTO

tahanson43206 · 2024-05-22 13:42:39

The Space Shuttle was an example of a Single Stage to Orbit vehicle that accepted a boost from solid rocket motors at launch.

I'm calling the Space Shuttle an SSTO vehicle for the simple reason that it lit it's own propulsion at lift off and it sustained that propulsion all the way to orbit.

This topic is offered for NewMars members who might want to focus upon technologies that can assist an SSTO during launch, much as the solid rocket boosters assisted the Space Shuttle.

Update 2024/06/04 .... clarification ... this topic is intended to support development of vertical launch assistance technology.

A new topic has been opened for horizontal or inclined launch assist technology.

(th)

Last edited by tahanson43206 (2024-06-04 10:38:43)

tahanson43206 · 2024-05-22 13:43:14

This post is reserved for an index to posts that NewMars members may contribute over time.

Update 2024/06/04...

tahanson43206 wrote:

While this topic has lost it's intended first customer, it remains available for development.
Coming out of the earlier discussions, we have some guidelines for future development...
1) Length of 1 kilometer
2) G force no greater than 5
Chemical or electromagnetic technologies are in play.
Physical energy storage such as compressed air is a possibility, but that seems like a long shot.
(th)

(th)

Last edited by tahanson43206 (2024-06-04 10:44:34)

tahanson43206 · 2024-05-22 13:45:19

This post is offered to show some alternative vertical launch systems not including the traditional methods.

I asked ChatGPT4o to think about the problem, while excluding aircraft, balloons and traditional side boosters.

Innovative Approaches to Initial Vertical Boost for Space Vessels
The challenge of providing an initial vertical boost to a space vessel without resorting to traditional chemical rockets, aircraft, or balloon launches is indeed a fascinating problem. Here are several innovative and speculative approaches that have been considered in various studies and discussions within the spaceflight community:
Electromagnetic Launch Systems
a. Railguns:
Railguns use electromagnetic forces to accelerate a projectile along a pair of conductive rails. Applied to space launch, a railgun could potentially launch a spacecraft at high velocities, reducing the need for initial rocket propulsion. However, the technical challenges include managing the extreme forces and heating involved.
b. Coilguns:
Similar to railguns, coilguns (or gauss guns) use a series of electromagnetic coils to accelerate a magnetic projectile. This system could theoretically be scaled up for spacecraft launches, though the power requirements and precision control are significant engineering hurdles.
Space Elevators
A space elevator consists of a tether anchored to the Earth at one end and extending into space, with a counterweight at the other end beyond geostationary orbit. Climbers would ascend the tether, providing a smooth, continuous ascent to space. The materials science required to create a tether strong enough (such as carbon nanotubes or graphene) is still under development.
Maglev Launch Systems
Magnetic levitation (maglev) technology, used in some high-speed trains, could be adapted to launch spacecraft. A maglev track could accelerate a vehicle along the ground to very high speeds before releasing it into a ballistic trajectory. This would reduce the amount of onboard propellant needed.
Tethered Launch Systems
a. Skyhooks:
A skyhook is a rotating tether in orbit that can "hook" a spacecraft from the ground or low altitude and fling it into a higher orbit. The rotational motion can transfer kinetic energy to the spacecraft. This concept requires precise timing and advanced materials for the tether.
b. Momentum Exchange Tethers:
These systems involve long tethers in space that can capture and fling spacecraft using momentum transfer. The tether would need to be anchored to a massive body or another spacecraft to conserve momentum.
Laser Propulsion
Laser propulsion involves ground-based or space-based lasers beaming energy to a spacecraft. The spacecraft would have a light-absorbing material or a propellant that vaporizes under the laser beam, producing thrust. This method could reduce the need for onboard fuel but requires significant advancements in laser technology and energy transmission.
Space Fountains
A space fountain consists of a stream of high-velocity particles (such as ionized gas) launched from the ground to an orbiting structure. The pressure of the particle stream supports the structure, and elevators travel along the stream. This method is still highly theoretical and would require groundbreaking developments in particle control and materials science.
Mass Drivers
Mass drivers are essentially electromagnetic catapults. They work by accelerating a spacecraft along a track using a series of magnets or coils. After reaching a high velocity, the spacecraft would continue on its trajectory, reducing the need for initial onboard propulsion. The system's length and the power requirements are significant challenges.
Ground-Based Beamed Energy Propulsion
This method involves ground-based microwave or laser arrays beaming energy to a spacecraft equipped with a heat exchanger. The received energy heats a working fluid, which is then expelled to produce thrust. This approach can reduce the need for chemical propellants onboard the spacecraft.
Considerations and Challenges
Material Science: Many of these concepts rely on materials that can withstand extreme forces and temperatures, which are still under development.
Power Requirements: Systems like railguns, coilguns, and maglev launches require immense amounts of power and precise control mechanisms.
Environmental Impact: High-energy launches can have significant environmental impacts, including noise and potential damage to the launch site.
Cost and Scalability: While these methods could reduce the cost of propellant, the initial infrastructure investment is substantial.
These innovative approaches show promise but require further research and development. Each method has its own set of technical, economic, and environmental challenges that must be overcome to make them viable alternatives to traditional rocket launches.

(th)

SpaceNut · 2024-05-22 17:02:11

It was considered a 1.5 stage since the boost was required to get motion started under hard acceleration that 3 shuttle engines could not perform no matter how much fuel it had. The requirement needed way more engines to perform this task.

Shuttle also dropped its tank as it was dead mass once empty.

tahanson43206 · 2024-05-22 17:32:35

For SpaceNut re #4

Thank you for adding the 1.5 idea to the topic!

It certainly has plenty of history.

I am standing by my analysis. The Shuttle fired it's engines at takeoff, and burned them all the way to orbit.

The fact that additional equipment was attached to help is irrelevant.

In my opinion, Shuttle WAS a model for the SSTO vehicles that will arrive on the scene.

The Two Stage To Orbit is clearly defined by the existence of two separate sets of engines that fire separately, after stage separation.

The vehicles that (I think) kbd512 and RGClark are discussing, and on the verge of designing, will be assisted with auxiliary hardware to achieve orbit.

The ** big ** difference is that whatever additional boost methods are used, they will all be reusable.

The Shuttle did NOT have to discard that big tank, but the decision was made to do so, and we have 100 or so clumps of aluminum in the Atlantic ocean.

List of Space Shuttle missions - Wikipedia
en.wikipedia.org › wiki › List_of_Space_Shuttle_missions
From 1981 to 2011 a total of 135 missions were flown, all launched from Kennedy Space Center (KSC) in Florida. During that time period the fleet logged 1,322 ...

(th)

SpaceNut · 2024-05-25 11:21:06

The shuttles SRB's were considered the 0.5 stage as they did not use the fuel in the external tank. https://en.wikipedia.org/wiki/Space_Shuttle

Stages 1.5[2]: 126, 140

https://www.nasa.gov/gallery/space-shut … -diagrams/

It dropped the ET due to lowering payload to orbit as a result of the dead mass and drag that it would create having it still attached.

Back to the topic in that we would not want to see a runway used for takeoff as it would need to be very long to achieve speed required to make lift plausible for a large craft.

https://en.wikipedia.org/wiki/Single-stage-to-orbit

SpaceNut · 2024-05-28 18:28:37

I am reminded that what goes up must come down and that with rockets it's about shape for both as the rocket takes on different drag and friction equations as a result of speed and pressures that its see's in both directions.

To land and take of vertically takes fuel and with the falcons 2 stages that first is not seeing the actual landing speeds from orbit. The same was also so far for the starship even with tps protection.

At this point I would say that we are stilll not on solid ground.

tahanson43206 · 2024-05-28 18:42:37

For SpaceNut re the SSTO argument ....

It appears you are sticking by the idea that Space Shuttle was not a true SSTO.

You have offered as evidence the fact that Space Shuttle had assistance at lift off by two solid fuel rockets.

I see that as irrelevant. The Shuttle lit it's engines and kept them lit all the way to orbit. That is the definition of a Single Stage to orbit.

There were no other stages.

It is true that the Shuttle lit a second set of engines after it ran out of fuel on the first set of engines.

I don't see that as significant. That was not a ** stage ** ... The Shuttle had carried those engines and the fuel along from the moment of lift off.

During various points in US military history, JATO units were fitted to aircraft to help them take off. The use of JATO units did not cause the military to call the aircraft less than an aircraft.

I have just posted a study by ChatGPT4o showing that RGClark's vision of a single stage to orbit might be possible. I'm looking forward to analysis of the presentation by our members.

(th)

SpaceNut · 2024-05-28 19:00:15

You can even take it up with kbd512 Oh, right. The 1.5 stage to orbit Space Shuttle with its 1,739,093kg of propellant mass and 2,635.925m^3 of propellant volume provided the same total impulse as a notional SSTO with 1,387.065m^3 LESS propellant volume and 210,488kg LESS propellant mass.

Lift planes are also considered a half stage for those as well.

Pegasus and a few others come to mind.

I think Nasa knows what a space shuttle was as it could not even leave the launch pad without the high thrust of the srb's so it's not an SSTO.

Also, anything that drops off is not part of the ssto designs as its not getting to orbit.

A falcon 9 is 2 stages and it weight is twice as much loaded at lift off.

Calliban · 2024-05-31 04:44:42

Taking Kbd512's mass estimates of a 2000te SSTO with a 40te payload. Could a launch assist system provide value for money?

I am going to assume that a steam cannon is used to accelerate the SSTO to an initial velocity of Mach 0.9 (300m/s). I also assume the steam cannon is 30% efficient and the steam is generated by forcing water through electrically heated rocks. The electricity has a unit cost of $0.1/kWh. How much would the electricity cost to run the launch assist?

Q = (mv^2/2) ÷ n = (0.5 x 2,000,000 x 300^2)/0.3 = 30GJ (80,000kWh)

Cost = $80,000 x 0.1 = $8000/launch.

Cost per kg payload = 8000/40,000 = $0.2/kg

Clearly, if the launch assist can boost meaningful payload by even 1% it is likely to pay for itself.
https://en.m.wikipedia.org/wiki/Rocket_sled_launch

'Due to factors including the exponential nature of the rocket equation and higher propulsive efficiency than if a rocket takes off stationary, a NASA Maglifter study estimated that a 270 m/s (600 mph) launch of an ELV rocket from a 3000-meter altitude mountain peak could increase payload to low Earth orbit by 80% compared to the same rocket from a conventional launch pad.[5] Mountains of such height are available within the mainland U.S. for the easiest logistics, or nearer to the Equator for a little more gain from Earth's rotation. Among other possibilities, a larger single-stage-to-orbit (SSTO) could be reduced in liftoff mass by 35% with such launch assist, dropping to 4 instead of 6 engines in one case considered.[5]'

This suggests that launch assist to 270m/s (Mach 0.8) would increase payload capacity by 80%. Or it could allow use of easier but lower performing propellants like LOX/CH4.

Last edited by Calliban (2024-05-31 04:52:01)

tahanson43206 · 2024-05-31 06:46:02

For Calliban re #10

Please develop your ideas for this system.

If kbd512 is willing to use such a system, if would allow him to reduce the size of his passenger transport, or to improve it's ability to carry out it's mission.

Either way, everyone would benefit from the addition of momentum at launch.

I would be interested in details, such as whether your proposed system could use sea water instead of desalinated water, which would require time and energy to prepare. In addition, the mechanical details of your design would be interesting.

Your design could be helpful to all large rocket vehicles, and not at some point in the future.

All large vehicles would benefit right now, when technology is not as advanced as it will be years from now.

One of your hand drawn sketches on engineering paper would be a good fit for this topic!

(th)

Calliban · 2024-05-31 08:52:26

One important design related question: What acceleration can we expect passengers and structure to withstand? At 5g, it takes 6 seconds to accelerate to 300m/s. At 10g, only 3 seconds. The higher the acceleration, the shorter the barrel length and the lower the capital cost. A 10g acceleration would be uncomfortable. But it would only last 3 seconds.

At 10g acceleration, barrel length will be 450m. At 5g, it is 900m.

Any thoughts?

Last edited by Calliban (2024-05-31 08:59:53)

tahanson43206 · 2024-05-31 13:51:25

For Calliban re #12

First, thanks for working this interesting problem!

Second... In case you missed it, which is certainly possible, kbd512 is thinking about shipping his passengers using net webbing to hold them like a Navy bunk, instead of the kind of upholstered couch SpaceX is using, and I assume Blue Origin is using. That sure does save weight, but I'm wondering about how high acceleration would affect the comfort/support of such devices.

A one kilometer initial acceleration at 5 G should be acceptable to most prospective passengers. The details of how acceleration levels are tolerated by humans should be available for study, since so much work has been done in this area for military equipment. It seems to me there is a ** lot ** of information posted in this forum, along with links to outside resources.

***
I have another question .... if the acceleration tube is a cylinder (as seems reasonable) would the vessel ignite engines after clearing the tube, as submarine launched ballistic missiles do?

Failure mode with 500 passengers on board would be spectacular, I would think.

***
Perhaps the passenger section can be accelerated away from the main body (somehow) if ignition fails.

(th)

SpaceNut · 2024-05-31 15:05:26

We did talk about the aircraft carrier launch system that was steam powered but also of the electrical version and of a sled as well.

Along with the launch cannon barrels and others in the past.

electromagnetic launch with microwave propulsion

kbd512 · 2024-05-31 18:46:24

Calliban,

Let's see if some back-of-napkin math arrives at an approximate answer, based upon NASA's testing criteria and safety factors. You're going to see some strange American units, because we do things the American way here, but work with me.

Load; Factory of Safety
A = All Margins
D = Discontinuities
M = Minimum
O = Uniform
U = Ultimate
Y = Yield

Proof: 46.2lbs/in^2; 1.0M
Max Compression: 20lbs/in^2; 1.5O, 2.0D, 1.1Y, 1.4U
Max Tension: 46.2lbs/in^2; 1.5O, 2.0D, 1.1Y, 1.4U
Internal Pressurization Failure: 1.0A

NASA Composite Tank Design Requirements
Diameter: 394in, Total Height: 413in, Tank Wall Height: 176in
Volume: 22,400ft^3
Max Design Pressure: 46.2psi
NASA-defined external loads (axial, shear, and moment)
Factors of Safety: Tank acreage 1.5; Composite joint 2.0
Material: IM7/977-2 Gr/Ep (government furnished, no choice)
Openings: 30in diameter, forward dome and aft dome / sump
Max Lamina Strain: 5000 μin/in (NASA specified to avoid microcracking)
Max Compression Strain: 3300 μin/in (see above; Poisson's effect from bi-directional loading)
Max Stabilization Pressure: 20psi

Notes:
IM7/977-2 is not the strongest stuff available by a longshot, but it's common here for the aerospace industry. As near as I can tell, 0.0026in thick tape face sheet lamina and 0.0052in thick tape / fiber tow lamina were used exclusively. The 0.0026in lamina was used to inhibit LH2 permeation of the composite, and overall, produces a stronger composite because there's less volume and variation in the resin fill between lamina. How much stronger is hard to say because there's so much other stuff that goes into layup strength. Details matter, but those weren't provided by NASA.

Rather than LH2 and LN2, which is what NASA used for their tests, let's instead use densified LOX (1,262kg/m^3) as our worst case load on the aft tank dome for 5g and 10g accelerations. We'll presume the resin matrix is LOX compatible and results in composites of identical strength. If this works for LOX, then it works for RP1 and LH2 (obviously, since NASA tested that).

Tank Volume: 22,400ft^3 / 634.29736m^3
Boeing Hexcel IM7 fiber / 977-2 resin Composite Tank Weight: 6,696lbs
Propellant Weight: 1,764,761lbs / 800,483kg
Total Weight: 1,771,457lbs / 803,521kg
Tank Diameter: 10.0076m / 394 inches (12.833ft)
Tank Radius: 5.0038m / 197 inches (16.416ft)
Surface Area of Tank Dome (not its actual surface area since it's not a perfect half-sphere) = 1,693.36ft^2

1g / Static Load on a completely full densified LOX Aft Tank Dome: 1,046lbs/ft^2 or 7.2647lbs/in^2
5g Load on Aft Tank Dome: 36.324lbs/in^2 <- Still within 46.2lbs/in^2
10g Load on Aft Tank Dome: 72.647lbs/in^2 <- This is well beyond design strength limits, even if the tank somehow survives

If this was T1100G or T1200 fiber tow with a CNT or Graphene toughened resin, then it would remain quite comfortably within limits for a 5g acceleration if the tank was the same weight, especially if it was fabicated exclusively from thin lamina, which is what I want to do. However, it will still fail at 10g, so that's out of the question unless we make the tank significantly stronger and lighter. I don't think that's possible without pure CNT composites. I'm actually after much higher strength and stiffness at the exact same weight as these test articles.

I'm well aware that the tank dome is not a perfect half sphere, and that due to the orientation of this vehicle, the load will not be perfectly transferred through the aft dome so some tangential loading will be transferred through part of the aft dome and part of the tank walls, and that the walls are absorbing the load and limiting the allowable strain / deformation from the launch acceleration loading, and that we will probably go over whatever strain values NASA deems "safe" for LH2 tanks, but this is not for a LH2 tank. There's probably a strain rate loading component in play here as well, because I know that high vs low strain rate loading of composites produces different results. If said propellant tank was accelerated at an acceptable rate, peaking at 5g or 10g straight up, relative to the surface of the Earth, then these estimates are reasonably close. Initial tank pressurization would need to be dynamically controlled to avoid over-pressurization at launch. I don't know how simple or complex that would be, and I don't think we do stuff like that very often, but I could be wrong.

As to human factors...

Even if the vehicle could survive 10g without issue, I would have serious reservations about subjecting most pilots to 10g, let alone people who are not physically trained to withstand that. Whenever you see stuff like this tested, they're using trained test pilots or acrobatic pilots. They'd probably need neck braces, which adds more weight and complexity, plus the still-present possibility of injury, which doesn't seem worth it. Steel and concrete are cheap. 900m isn't as long as the runways that the little planes land on around here. Injuries sustained while people are in the process of being launched into orbit doesn't seem particularly cost-effective to me, no matter how cheap the launch track happens to be. They need to be in good health when they arrive, because we just spent boat loads of money to train, equip, launch, and deliver them to Mars.

Since this vehicle has to have a 1.5:1 thrust-to-weight ratio, you don't need to supply quite as much power to the EMALS, so we have that going for us.

What's the moral of this story?

It's a big heavy rocket, not a F-16.

tahanson43206 · 2024-05-31 20:59:09

This is for Calliban

Note taken of kdb512's post #15

I conclude that 5 G would be acceptable for the initial boost.

We have not yet seen (or at least ** I ** have not seen) a projection of G forces on the passengers for the passengers and crew of the 500 passenger ship.

Hopefully that will show up in the near future.

In the meantime, for Calliban ...

Your initial suggestion in the current round was to make steam by passing water through hot rocks.

I'd like ask if gunpowder might provide an example of a stored energy system (not gunpowder, but something that released energy slowly as is the case with gunpowder)

I think this is more of a physics question than a chemical one, although chemistry is what I'm asking about....

Suppose you had ping pong balls filled with hydrogen and oxygen that are packed into a cylinder like a military gun, with a shell on top that is to be accelerated out the tube. I'm presuming no leakage is occurring prior to ignition. If the ping pong balls at the bottom of the stack were punctured and the mixture of gases ignited, am I correct in thinking that the wave front would proceed more slowly than would be the case if the gases were mixed together. Is something like this a possibility for your huge launcher of kbd512's 2.8 megaton vehicle?

If it would work for a vessel that size, then I would expect it to work for a smaller vessel.

(th)

Last edited by tahanson43206 (2024-05-31 21:00:04)

kbd512 · 2024-06-01 18:54:27

What I've noticed about air launches, catapult assist launches, as well as high thrust-to-weight ratio vehicles that use forward flight with a little bit of lift, is a significant reduction in gravity losses. Any gravity loss reduction translates into more propellant available to achieve higher orbits or more payload if thrust is the same.

I wrote a very simple pl/sql program (about 40 lines of code) to determine what propellant mass reduction would be feasible for the same final velocity produced by 2,000t of propellant. It doesn't take into account gravity or drag losses, but a 300m/s initial acceleration reduces the required propellant mass by 150,000kg, or about 7.5%. That's pretty significant.

The program I wrote limits vehicle acceleration rate to 5g or 49.03325m/s, so the engines are gradually throttled down as the flight progresses, to avoid over-stressing the airframe. Some engines would have to be shut off while others are run at full power to maximize Isp.

Fi: 30,891kN; Ff: 4,987kN
Mi: 1,950,000kg; Mp: 1,850,000kg; Mf: 100,000kg
Total Flight Duration: 265s (4 minutes, 25 seconds)
Max-g: 143s (5g maintained to burnout, just over 2 minutes)
Vi: 300m/s
Vf: 10,077.407m/s

Alternatively, for the same 2,000t propellant load as the original vehicle design, payload increases by 14,000kg. Since we don't really need additional payload for the passengers, that extra mass can go into structurally strengthening the vehicle to survive launch and landing.

I'd be interested in pursuing this further, because it makes the vehicle design easier.

Calliban · 2024-06-02 06:58:32

Kbd512, please could you provide a summary of the takeoff mass and dimensions of your proposed SSTO? I will then look at options for the cannon.

There are a great many propulsion options for accelerating a vehicle to 300m/s. What we are really aiming for is a minimum cost design. Energy and propellant costs are small for such a device, really regardless of the efficiency of propulsion. But capital cost is going to be the driver of total cost in the case of a launch assist.

Which explains why nobody has built anything like this to date. It only makes sense if the number of launches exceeds a threshold, where the value of increased payload capacity exceeds the marginal capital cost of the launch assist. It is rather like building a road. It becomes more and more desirable as the number of tonne-miles travelled along a route increases. Which is why we see ice road truckers traversing rough terrain when delivering freight to one horse towns in the Canadian wilderness. A road would make the journey quicker and more fuel efficient. But the marginal capital cost of a road would in those cases increase the cost of haulage, because the volume of freight travelling those routes is too low. In the case of rocket launch to orbit, as the number of rocket launches increases it becomes increasingly desirable to pursue infrastructure options that can reduce cost and increase payload
*****************************

Additional: As we are launching at speeds <Mach 1, we could use compressed air to power the cannon. Staged axial compressors could be used to fill a PCRV prior to launch. Launching the sabot and rocket would then require just opening a valve between the storage vessel and the bottom of the tube. Really simple. Steam has the problem that saturated water droplets will form as it expands, which would corrode the inside of the barrel. But air can be dried between compression stages. So the air that is used to propel the rocket will be extremely dry. A speed of 300m/s is about 1000ft/s. There are air rifles that can do this.
https://www.outdoorlife.com/gear/most-p … air-rifle/

Last edited by Calliban (2024-06-02 14:57:04)

tahanson43206 · 2024-06-02 16:24:10

For all NewMars members and readers ...

This topic is about Vertical Launch Assist Technologies for SSTO

This topic is NOT about any other direction for launch assistance.

If we need a topic for Horizontal Launch Assist Technologies for SSTO, that is an option.

(th)

kbd512 · 2024-06-02 16:27:27

Calliban,

The vertical launch and horizontal landing vehicle was to have these mass values:

Total Vehicle Gross Liftoff Mass (Mi): 2,100,000kg
Total Propellant Mass (Mp): 2,000,000kg
Final Mass (Mf): 100,000kg (60,000kg vehicle; 40,000kg for 500 passengers; no cargo- humans in pressure suits only)
Sea Level Thrust: 3,150,000kgf / 30,891kN

Calliban · 2024-06-02 18:26:17

kbd512 wrote:

Calliban,
The vertical launch and horizontal landing vehicle was to have these mass values:
Total Vehicle Gross Liftoff Mass (Mi): 2,100,000kg
Total Propellant Mass (Mp): 2,000,000kg
Final Mass (Mf): 100,000kg (60,000kg vehicle; 40,000kg for 500 passengers; no cargo- humans in pressure suits only)
Sea Level Thrust: 3,150,000kgf / 30,891kN

Thanks. I also need an approximate diameter. With that I can calculate the required barrel pressure needed to produce the required acceleration.

For a muzzle velocity of 300m/s (1000ft/s) and an acceleration of 5g (6g inc gravity), the barrel must be 918m (2985') long. That is a long barrel. If we can manage a 10g acceleration overall, that can be cut down to 1658'.

I think the barrel needs to be breach loaded, rather than top loaded. We load the SSTO onto a sabot and then drive it through a side door in the barrel. The side door is closed a sealed before firing. Muzzle loading is only really practical if we drill the barrel as a 2985' deep shaft into the Earth. The cost of that is going to be a lot higher than a 2985' tall steel pipe. For stability, the barrel will be braced to the ground with bracing cables continuously along its length. I initially thought steam would be the best propellant. But compressed air seems better, as it can be liw moisture.

Last edited by Calliban (2024-06-02 18:41:51)

tahanson43206 · 2024-06-02 19:46:42

For Calliban re diameter ...

kbd512 is going to give you a diameter soon. I can tell you now it will be less than 33 feet.

It seems to me you will have lots of customers for this service, so if you make the platform large enough you can accommodate a variety of vehicles.

You'd be the only game in town for a long time, so it seems to me it would make sense to plan for the larger vehicles and be able to serve the smaller ones.

(th)

kbd512 · 2024-06-02 20:13:35

Calliban,

Are you trying to put the entire vehicle inside a gun barrel of some kind?

If so, I don't think that's going to work. This vehicle is not an artillery projectile, even if it roughly resembles one.

Approximate length, excluding tail fins will be around 57m at most, about the same height as the Atlas V with its 11m payload fairing. It could end up being significantly longer, though. I'm still working through the design implications. As of right now, fuselage diameter will be approximately 7m, but it won't be exactly 7m anywhere along the fuselage. It needs to be a long / slender lifting body design with wings, but the fuselage has an oval fuselage cross-section.

The approximate vehicle shape is shown below:

Notice how it has wings. They're fairly small, granted, but they're still there. It will also have tail fins for directional stability. Those features may be incompatible with a gun barrel. I was under the impression that the vehicle would have hard points on its belly for hooks on a truck that is connected to a "gun barrel" containing a piston to supply the required pressure, like a regular steam catapult aboard an aircraft carrier, or some kind of EMALS.

My vehicle would have a "pointy" nose, because the image shown above was for an air-breathing SSTO concept. My SSTO concept uses pure rocket thrust, so that large gaping hole shown in the nose of the vehicle above would be part of the passenger compartment.

Calliban · 2024-06-04 04:25:14

I think it is sensible to redefine the concept as 'launch assist' rather than 'vertical launch assist'. I initially favoured vertical launch, because this is how Starship is designed to launch. But as SSTO is a new concept designed from scratch, there is no need to be constrained by engineering legacy. Additionally, it appears that horizontal launch, or at least launch along an incline, is more optimal from the viewpoint of reducing gravity losses. This seems counter intuitive, until you realise that the Earth surface is curved. Even an entirely horizontal launch, still has a vertical velocity vector w.r.t Earth's gravitational equipotential lines.

It is much cheaper to build a horizontal launch assist and it isn't constrained by topography. It allows for a higher velocity launch assist at more modest acceleration. It is therefore better. To avoid centifugal acceleration, the horizontal launch track will need a slight slope away from Earth surface, because the Earth curves beneath it.

The baseline concept is for a 50m/s2 constant acceleration, providing a 300m/s launch assist. This requires a track length of 900m, or 2925'. The propulsion method is open at this point.
*************************

A steam rocket perhaps? Assuming we heat water close to its critical point 372°C and assuming a 30% conversion of heat into kinetic energy, exhaust velocity will be ~1km/s. This is quite a simple device. A steel pressure vessel full of hot water at 370°C. Upon opening a valve, hot water expands into a DeLavelle nozzle, where it flashes to steam. Due to the mass of the steel vessel, this design has a limited final velocity, no more than 0.5km/s. But should be entirely capable of reaching a velocity of 300m/s. As the tank empties, the pressure declines. The temperature declines as part of the energy within the remaining hot water flashes to steam to fill the empty tank space. The valve will need to throttle open as the tank opens to maintain flowrate and thrust.

Last edited by Calliban (2024-06-04 05:23:08)

tahanson43206 · 2024-06-04 06:10:07

For Calliban re #24

This topic is set up to develop for the vertical case.

In light of your interest in an incline, I will create a topic for you to develop the incline option.

If we can persuade you to indulge us in ** this ** topic, the vertical launch option remains the only one that looks practical for a launch from Texas, due to the population that would be under the flight path.

A 1 kilometer deep excavation for a vertical launch assist facility would be difficult but well within the capability of humans at this time.

While you will have the incline topic to develop separately, please allocate a small part of your (admittedly limited) time and energy to the vertical problem.

(th)

New Mars Forums

Announcement

#1 2024-05-22 13:42:39

Vertical Launch Assist Technologies for SSTO

#2 2024-05-22 13:43:14

Re: Vertical Launch Assist Technologies for SSTO

#3 2024-05-22 13:45:19

Re: Vertical Launch Assist Technologies for SSTO

Innovative Approaches to Initial Vertical Boost for Space Vessels

Considerations and Challenges

#4 2024-05-22 17:02:11

Re: Vertical Launch Assist Technologies for SSTO

#5 2024-05-22 17:32:35

Re: Vertical Launch Assist Technologies for SSTO

#6 2024-05-25 11:21:06

Re: Vertical Launch Assist Technologies for SSTO

#7 2024-05-28 18:28:37

Re: Vertical Launch Assist Technologies for SSTO

#8 2024-05-28 18:42:37

Re: Vertical Launch Assist Technologies for SSTO

#9 2024-05-28 19:00:15

Re: Vertical Launch Assist Technologies for SSTO

#10 2024-05-31 04:44:42

Re: Vertical Launch Assist Technologies for SSTO

#11 2024-05-31 06:46:02

Re: Vertical Launch Assist Technologies for SSTO

#12 2024-05-31 08:52:26

Re: Vertical Launch Assist Technologies for SSTO

#13 2024-05-31 13:51:25

Re: Vertical Launch Assist Technologies for SSTO

#14 2024-05-31 15:05:26

Re: Vertical Launch Assist Technologies for SSTO

#15 2024-05-31 18:46:24

Re: Vertical Launch Assist Technologies for SSTO

#16 2024-05-31 20:59:09

Re: Vertical Launch Assist Technologies for SSTO

#17 2024-06-01 18:54:27

Re: Vertical Launch Assist Technologies for SSTO

#18 2024-06-02 06:58:32

Re: Vertical Launch Assist Technologies for SSTO

#19 2024-06-02 16:24:10

Re: Vertical Launch Assist Technologies for SSTO

#20 2024-06-02 16:27:27

Re: Vertical Launch Assist Technologies for SSTO

#21 2024-06-02 18:26:17

Re: Vertical Launch Assist Technologies for SSTO

#22 2024-06-02 19:46:42

Re: Vertical Launch Assist Technologies for SSTO

#23 2024-06-02 20:13:35

Re: Vertical Launch Assist Technologies for SSTO

#24 2024-06-04 04:25:14

Re: Vertical Launch Assist Technologies for SSTO

#25 2024-06-04 06:10:07

Re: Vertical Launch Assist Technologies for SSTO

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