kbd512 Postings

kbd512 · 2024-05-18 12:41:24

I had to break that post up into multiple parts, and for some reason the software accepted the text when broken up as it was, but not as a whole. Strange, but whatever.

tahanson43206 · 2024-05-18 13:30:10

For kbd512 ... two items ...

First, thanks for giving so much thought to the possible structure of a forum in "Projects" that would be dedicated to SSTO Passenger Transport

Second, I am happy to report that AISE seems to have gone away with the updates to FluxBB 1.5.11.

I am highly motivated to encourage the Admins to accept the updated software. If there is more testing needed, let's do it!

Every member is welcome to help with testing the revised software.

Everyone who had an account last fall (of 2023) is able to log in and test the software. There is no risk. We are running on a copy of the database.

We would ** really ** like to have any remaining bugs identified before we upgrade.

http://40.75.112.55/forums/FluxBB/misc.php?action=rules

For kbd512 ... please write SpaceNut directly at Housekeeping if you would like to encourage him to create the new Projects Category, and a new SSTO Passenger Transport forum. SpaceNut will need html to describe the new forum. AISE seems sensitive when html is entered into a post. You may have to design the html with fake signals like "LT" for the less than character.

Since you are an Admin, you can see what's needed by looking at the forum definitions in the clone or in NewMars Prime.

(th)

tahanson43206 · 2024-05-21 22:21:10

For kbd512 re https://newmars.com/forums/viewtopic.ph … 59#p223459

*** Awe *** Some !!! ***

I am delighted to have inspired your post!

I almost miss the Soviets .... But then, I never had to shoot any.

Quick checking ... this is the kbd512 topic so I'll toss this out .... Greg Stanley (at LinkedIn) reposted a note from a gent who wrote about Taiwan.

The note was based upon what seems to have been an analysis indicating that the Chinese might have their hands full if they decide to invade Taiwan in the modern age. The implication seems to be that in the modern age, the defense has a better position than the offense. All those Chinese ships and planes would be sitting ducks in the strait while they attempt to reach the island.

Sometime in the past day or so, I caught a report on the history of the China/Taiwan interactions. Formosa was the former name of the island. It was invaded by a Chinese emperor back in the days of sailing ships, and it was a wholly "owned" Chinese property until the Nationalists took over in the 20th Century. I suppose some would argue it still is.

I've seen/heard analysis suggesting the Xi may decide to make his move before he gets too much older.

(th)

tahanson43206 · 2024-05-22 06:17:06

For kbd512 re SSTO initiative

This post is to offer encouragement.

We have a lot of talent in this community, but talent alone will not lead to achievement.

It takes a combination of talents, and a lot of hard work, to bring about self-sustaining change in the Real Universe.

It also takes a tolerance for risk, combined with good judgement, combined with some luck.

I'd like to remind you that when PhotonBytes joined the community, he was working with a startup that was thinking about a design for a space plane of some kind. I'd like to remind you (and all our members and readers) that PhotonBytes provided a graphic image of a possible design for a shuttle-like craft with a lifting body shape.

There should be US national interest in the concept you've been describing, for defense, for emergency assistance and perhaps for other purposes I'm not aware of.

It will take building a team of extremely reliable people to win over potential funders. Raw intelligence is insufficient. Demonstrated performance is the key to convincing funders that an individual can be trusted with precious funds. Dr. Zubrin is a good example of an individual who has demonstrated a high level of performance over many years, and as a reward he has receive substantial funding from literally thousands of individuals in the form of Society membership, and in the form of major grants, such as the one from Blue Origin.

Raw intelligence is most certainly a requirement for success in the SSTO venture.

However, this forum has plenty of raw intelligence.

The SSTO project appears to be achievable in some form, with the benefits of 100% reusability the substantial reward for success.

This post is intended to offer support and encouragement for everyone who is going to be assisting kbd512 to achieve this laudable goal.

Let's set a goal of 10 years and see if we can come in with a successful test flight ahead of that target.

(th)

tahanson43206 · 2024-05-23 06:51:11

For kbd512 re SSTO initiative ...

Your latest posts in the new SSTO topic are encouraging to me, as a lay reader ...

Please consider asking Dr. Johnson to scrub your numbers....

You may well be onto something promising, with your concept (as I understand it) of using a Space Shuttle External Tank as a model for a design, while changing from LH2 to a more dense propellant.

It seems to me there is a potential benefit to using flyback liquid boosters to help put the vessel you are designing into motion.

Elon's Falcon Heavy shows what that might look like.

(th)

kbd512 · 2024-05-23 09:33:07

tahanson43206,

There's always a potential benefit to be had by mounting the orbital portion of a vehicle atop a large booster stage, but the focus of the topic is SSTO, so that's what I'm looking at. As we can see from the raw numbers, the payload we're aiming for is rather meager in relation to the liftoff mass, at 1.9%. If the actual payload performance capability is closer to 110t, then 5.2% is a very respectable payload mass fraction for a SSTO. However, the goal is not to evaluate what's most practical. I think a TSTO with Merlin or Raptor engine technology wins that argument rather convincingly, but not without a cost. Falcon Heavy's payload performance, in fully expended mode of operation, is only 4.5%, because the gas generator cycle has a much lower Isp than staged combustion. The realistically achievable Isp "sweet spot" for SSTO seems to be between 310s and 380s, because that implies dense propellants that provide lots of thrust from lightweight engines. If LH2 engine thrust-to-weight was comparable to LCH4 or RP1, then even the propellant tank volume disadvantage might be solvable, but gelled LH2 (70% LCH4 with 30% LH2 by weight) reduces volume by about 2/3rds, because from actual experimentation, the Isp only goes down to 410s from 460s while propellant tank volume equates to neat LCH4 propellant tank volume. That makes SSTO "even more doable".

Ergo, this is why Specific Impulse achieved by the engine remains an important factor between comparable Density Impulse liquid propellants. Neat LH2 has such an absurdly low Density Impulse, despite its incredible Specific Impulse, that in the best case scenario, the propellant tank volume and therefore weight must increase by 2/3rds when compared to LCH4 or RP1, to provide the same Total Impulse (total kinetic energy imparted to the launch vehicle to accelerate to orbital velocity). Total Impulse is what accelerates a vehicle to orbital velocity, after all. The higher Isp of Raptor's LCH4 fueled full-flow staged combustion engines, combined with an adequate thrust-to-weight ratio, means a lighter dry mass vehicle remains more performant. Shocking (not), but true. Incidentally, Falcon Heavy's dry mass is 72,300kg, with the booster stages comprising 66,600kg, mostly Al-2195, of the total. If Merlin engines had better Isp and the propellant tanks were lighter / stronger / stiffer, then the entire vehicle could be pushed into orbit with a useful payload.

As always, GW and anyone else who wishes to do so should feel completely free to poke holes in my logic and calculations. If I'm wrong, then I would like to know how and why, because I actually like learning from past mistakes. This isn't an ego or vanity project for me. I'm genuinely curious to explore what is possible, within the realm of extant materials science and engine performance. I have also freely acknowledged that if we applied the same materials and engine tech to a TSTO, then the TSTO would win the payload performance argument rather convincingly. That's just basic non-repealable physics in action.

In the mean time, I will continue to explore "the art of the possible", with an acceptance of the limits of practicality. To wit, very high specific strength or very high modulus (very high resistance to deformation under load) Carbon Fiber technology, and extreme engine TWR capability, is what makes SSTO so interesting to me. Is that enough? I don't know, which is why I continue to dive deeper to arrive at something approximating a reasonable answer regarding the limits of modern materials and conventional chemical rocket engines.

tahanson43206 · 2024-05-23 20:04:55

for kbd512 .... Your reply in Post #56 shows that I failed to clearly explain what I was thinking about.

In another topic, SpaceNut asserted that the Space Shuttle was not a true SSTO, and he called it a (1.5) version.

I do not agree. The Space Shuttle was most certainly a true SSTO. It lit it's engines on the ground, and kept them lit all the way to orbit.

SpaceNut pointed out that the Shuttle discarded the external tank, and that is certainly true, but the vessel you are designing could receive launch support from side-by-side boosters that fly back to base, unlike the solid fuel boosters or the external tank.

The vessel you are designing will light it's engines on the ground (as I understand your vision) and keep them lit all the way to orbit. The side-by-side boosters can help the vehicle you are designing to gain momentum in the early stage of flight.

That is what I meant about the Falcon Heavy being an example. The two side-by-side boosters that help Falcon Heavy during the early phase of the flight are able to return to base, so are completely reusable.

This has nothing to do with stacking one vehicle on top of another. That would be a Two Stage to Orbit design.

(th)

tahanson43206 · 2024-05-24 06:14:23

For kbd512 re new SSTO design topic ...

http://newmars.com/forums/viewtopic.php … 08#p223508

This latest initiative of yours keeps coming along nicely!

Best wishes for continued inspiration and reliable power to the equipment you're using!

I understand weather is challenging out your way.

I noticed the reference to Tesla .... "should" rather than "could" ....

Your work so far seems to assume landing on a runway with wheels.

You could reduce weight and complexity by landing on water.

If you make that minor adjustment, you have a **lot** of potential landing area available.

It seems to me a design patent might be possible. You're using already patented ideas, but combining them in a new way which I'm pretty sure ** can ** be patented as a design. This could then be the basis for writing proposals to entities who might participate in the project.

You've invited others to take a look at your work and that's good.

The design patent process may provide an opportunity to subject the design to professional scrutiny.

(th)

tahanson43206 · 2024-05-24 08:00:33

For kbd512 ...
This is a reminder that you have a member of this group who is part of an orbiter development project. At some point an idea or a set of ideas needs to attract support, or it will never amount to anything.

PhotonBytes wrote:

Orbiter Re-entry Path
http://photonbytes.com/wp-content/uploa … eentry.gif
We ran the CFD from Mach 0 - 25 and altitudes 0 - 105 km and plan to do ascent and reentry optimization next. Tom is right about the 40 deg max attack angle. We thank him for his input! We were planning no greater than 20 degrees to stay stable.

http://photonbytes.com/wp-content/uploa … lender.png
http://photonbytes.com/wp-content/uploa … hmixer.png
Meshmixer loads the STL with colors and is a tiny installation compared to Blender. Blender only shows the colors on the PLY import, which is an even bigger file than the STL with colors embedded.
https://meshmixer.com/
We uploaded the PLY file and added it to the 'Files' page with HTTP instruction to download rather than open the file.
http://space-plane.org/files.htm
With a simple switch in Blender you can display STL in color but it doesnt understand Vertex Color when loading STL so we use a PLY file for that.

(th)

kbd512 · 2024-05-24 09:18:50

tahanson43206,

Believe it or not, last night I did consider water landings. My envisioned design looks an awful lot like a flying boat hull. I would dearly love to delete the landing gear weight and complexity entirely. The question is whether or not the TPS could survive contact with the water at high speeds typical of lifting bodies used by winged spacecraft. I don't know if such a thing is possible. The TPS tiles are so light that damage is highly probable. If the TPS was primarily UHTCs and BNNT / aerogel fabrics, then water landing looks like a much more attractive solution.

As you stated, the runway length is functionally infinite and the Earth's surface is mostly water, which makes finding a suitable landing area off the coast of Cape Canaveral much easier to do. Runways capable of supporting the vehicle weight per unit area when using rubber tires are actually few and far between. It's not about total vehicle weight, it's about weight distributed by the landing gear per unit area, and a tire's contact patch with the ground is rather small, which is why they roll so well on hard surfaces.

I didn't propose the use of tracks just because I wanted to be "different". The Space Shuttle's ground pressure was such that it could not land on "any old runway of appropriate length". The very high tire inflation pressure, now typical of modern heavy airliners, was a direct result of ground pressure and keeping the tired inflated under heavy landing loads. The work done on tracked landing gear was limited to primitive early attempts between the 1930s to the 1950s. Those arrangements were generally much heavier than tires, but ground pressure was reduced to about 1/3rd of what it was using wheels. That made landing on ground that would cause conventional main gear wheels to "sink" or "dig in" then became possible. They obviously didn't have access to modern materials.

My design goal is to not "go over" the weight of the Space Shuttle landing gear, whatever the selected solution may be. With LOX/RP1 tanks, max landing weight and speed is the same as the Space Shuttle, which means no "reinvention of the wheel" is required.

I will make a mental note to investigate the loads created by water landings so I can evaluate whether or not the tiles will survive the impact loading. Perhaps a compromise solution, such as water skis can be fitted that are much lighter than wheels or tracks for the loads they will readily support, as well as far less stowage volume in the wing so that the wings can be thinner / more "glider-like", yet allow the aircraft to slow significantly before any tiles make contact with the water. Overall, water landing is a very attractive solution if no TPS damage occurs. Flotation is not a problem at all. This thing will float like a cork if either propellant tank or the passenger compartment remains intact. Sea water doesn't damage composites the way it does metals, nor does dousing the tiles in cold water (this has been tested). The entire airframe and the engine nozzles are composites, so a good fresh water spray will remove salt residues. Only attachment bolts, pins, landing gear pistons, and the enclosed / protected engine turbomachinery are subject to corrosion damage. Those parts will have Silicon coatings to resist corrosion.

tahanson43206 · 2024-05-24 11:01:24

For kbd512 ....

Try this ....

Heat shield on one side, water landing on the other.

If the ship is automated and passengers are delivered to destination, the ship doesn't care if it is up or down.

If the passengers are still on board for whatever reason, they get to experience landing on their heads.

(th)

kbd512 · 2024-05-24 11:38:38

tahanson43206,

Ideally, we'd like to avoid "landing on our heads". To the extent possible, I want to avoid unusual solutions to problems that have already been adequately solved.

Flying boats land on water using boat hulls or water skis (most use boat hulls, but a few use ski outriggers, mainly to support the wings). The Convair F2Y Sea Dart (amphibious fighter jet prototype) famously used water skis to land, so the hull itself did not smack the water at high speed. It was the only supersonic seaplane. It disintegrated in mid-air, killing the pilot (pilot error- grossly exceeded airframe limitations during maneuvering). 5 were built and tested. I think the water ski solution could work, though. The key is not having water directly strike the hull at 200mph, hence the ski-based solution.

Sea Dart Takeoff / Landing:

Sea Dart in Flight (showing water ski landing gear):

Sea Dart in the Water:

They did all kinds of crazy things in the 1950s- supersonic amphibious fighters with water ski landing gear, nuclear powered bombers, nuclear powered trains, hypersonic rocket planes, transistor and integrated circuit experimentation, first airborne computers, first practical photovoltaics, and the list goes on. It was a magical time for engineering innovation, even if some things weren't practical back then. Nobody thought they "couldn't". Instead, they asked themselves, "Well, what if we can? Let's just try it so we can figure out if it works or not?"

Runway landings almost always involve tires, unless your wheel is missing or your gear won't extend, and then you're a grounded ship.

Tracks were only proposed to lower the ground pressure, as well as opening up runway options. Off-runway landings are still a non-starter, but there's many more landing options with 1/3rd of the normal ground pressure.

tahanson43206 · 2024-05-24 12:30:57

For kbd512 re #62

Thanks for the image and history of that remarkable experiment!

Regarding landing on you head.... That would only be a problem if your are thinking of flying passengers back from orbit in this vehicle.

It is possible you are thinking of returning passengers from orbit in 500 person lots.

It seems to me it would make a lot of sense to let the small vehicle market take care of that.

Vehicles such as the Dream Chaser will (if successful) carry small numbers of people so the risks will be spread out over the population who need to return from space.

If you return 500 person vehicle without passenges and use automation to control the flight, then no one would be on their heads.

The advantage is that the skis will not be subject to heating during return from orbit.

(tr)

kbd512 · 2024-05-24 14:17:02

tahanson43206,

If there's an issue with making orbit, then all 500 passengers are coming back to Earth, like it or not, which is why this SSTO vehicle has to be capable of doing that. If small numbers of people return to Earth for reasons not related to launch failure, then yes, smaller vehicles could take them back, provided that those vehicles are already in orbit or slated to be launched. 500 passengers was selected on the basis of being the largest number of passengers that Starship could reasonably launch using the proposed seating scheme. That was also the largest number of passengers I could fit on a single large ship that could spiral out from LEO using near-term electric propulsion technology.

Incidentally, 500 is also a number that corresponds with a typical maximum number of passengers carried by an A380 or 747. Technically, those super jumbos can carry 600 to 800 people, but in practice 500 is more typical. Thus, 500 is "super jumbo capacity" to orbit.

Could you build an even larger vehicle?

Sure. This vehicle's liftoff thrust is already just below that of the Space Shuttle or Saturn V.

How big should we build it before there's a demonstrated requirement for larger transport vehicles?

I think 500 is plenty of capacity for now. That corresponds with the entire ship's complement for a Virginia class nuclear powered guided missile cruiser. If we operated a squadron of these SSTOs, then RobertDyck's much larger "large ship", would be filled to capacity in about 24 hours. That's enough lift capacity, over about 6 months, to populate a colony of a million people on Mars, or 1.825M per year. If that's still not enough, then we build more vehicles. Yes, money can always be spent to "build it bigger", but to what end? Real airline transport fleets operate multiple planes, rather than attempting to deliver a month's worth of passengers in a single flight.

Icon of the Seas, one of the largest cruise ships ever built, holds 10,000 people. A squadron of these SSTOs would fill that ship to capacity in less than 2 days, at a flight rate of 1 flight per plane per day, which seems reasonable. Flying more often than that probably only succeeds in creating a traffic jam.

During the next 50 years, based purely on present demographics trends, Earth's entire population will shrink by half. Until we secure more natural resources from other planets, there are simply not enough people and machines available to "do more".

Someone, who shall remain nameless, had better get on with the process of designing and building that large ship, because these SSTO vehicles will have no trouble at all with delivering the passengers in a timely manner. Tell that man to worry about the precise location of the beer tap after the hull is complete.

tahanson43206 · 2024-05-29 07:26:35

For kbd512 ....

After doing a bit of searching, I've come to the conclusion that the human race has not yet achieved fully reusable Two Stage to Orbit, let alone a true Single Stage to Orbit, let alone with a reusable orbiter.

Thus, the field appears to be wide open for you and RGClark to design a true SSTO.

You've been working on a 500 passenger vehicle recently, and that is certainly a worthy undertaking. However, there may be an opportunity to hone your skills, and to work out procedures, if you aim a bit lower for your first outing.

RGClark has offered 200 tons as a reasonable level for a first try, and ChatGPT4o seems to think that 200 tons of propellant would put 25 tons of vehicle and payload into LEO.

Apparently the definition of SSTO is a bit restrictive, in that nothing can be discarded by the vehicle on the way to orbit. Apparently that excludes sensible ideas such as side boosters, as were used by the Space Shuttle.

Can you design a space vehicle that can reach orbit with precisely 200 tons of propellant?

(th)

kbd512 · 2024-05-29 13:39:16

tahanson43206,

Smaller launch vehicles suffer from reduced payload performance, due to that pesky cube-square law (propellant volume enclosed by a given surface area of material doesn't increase at the same rate as the volume itself), plus the higher tank pressurization required to feed the main engines. The payload mass fraction gets consumed by the dry mass of the rocket and engines with LH2.

500m^3 of LOX/LH2 propellant volume to realistically drive 10t of useful payload all the way to orbit. As you scale-up, the tank and engine mass required starts to cannibalize your payload. The propellant mass figure looks great, but it doesn't translate to vehicle dry weight, not due to strength, but stiffness. That is why RP1 looks so attractive. T1100G has tensile strength galore, so doubling the propellant mass is not much of an issue, especially when engine mass also decreases by 2.67X, but not enough stiffness to increase the volume by 50%+. We can make 1,000ksi composites right now. We're already doing it at small scale. Stiffness is no better than a strong steel alloy or Tungsten. You can get 2X or 3X more stiffness with high modulus fiber, but only at great cost in strength and ability to resist impact at cryogenic temperatures. That said, the "normal" engineering solution involves using geometry and stiffeners to make that thin tank wall rigid to survive the aero loads and propellant slosh. Mixing and matching fibers to tweak for the desired mechanical properties can be done, but only very carefully, and again, there are limits. Get it wrong and your tank is neither stiff nor strong enough, and it's more prone to cracking / fracture of the fibers. Overall, using geometry tends to be a better solution, but not the lightest solution. High modulus / "astonishingly stiff" fiber is also astonishingly expensive compared to high strength fiber.

A straightforward Delta-V calculation shows 200t of propellant with a 409s avg Isp and 20t total dry mass results in 9,235.48m/s change in velocity. That is not enough to attain orbital velocity after drag and gravity losses are factored in. Realistic ranges start between 9.5km/s and 9.8km/s. I've been using 10,044km/s in all of my mass calculations. With that Delta-V, which provides a possibility of modestly higher orbits with reduced payloads such s 200km, I get 16,348kg as the total dry mass fraction (rocket plus any payload).

A 75:1 LOX/LH2 engine would weigh 4,000kg to provide 300,000kgf (a staged combustion RS-68 by any other name) of liftoff thrust. A T1100G composite should allow for the propellant tanks to weigh 1% of the propellant weight, so 2,000kg. I'd factor in another 250kg for all other systems, payload fairing, etc. That means the vehicle dry mass fraction is about 6,250kg, or 3.03% of the wet mass, so you get to keep 10,098kg / 10t of payload. That's the mass efficiency penalty paid for using low-density propellant and low-thrust rocket engines.

337,600kg of LOX/RP1, with 338.3s of Isp, provides the same 10,044m/s of Delta-V, in 276m^3 of total volume, vs 506m^3 for LH2- a 54.5% decrease. Wet mass is 353,948kg. Engine mass reduces to 2,655kg to provide 1.5:1 TWR. Even if the tank requires more mass for sufficient tensile strength, which it does not, it just became a whole lot stiffer for a given mass because it's 50% smaller.

The limitation on the composites now in use are stiffness / mechanical properties in different planes / thermal loads, but not tensile strength. That's why large composite structures can be so light, relative to any kind of metal. You are not going to tear a properly made composite structure asunder without using inordinately more force than is required to tear paper thin metal apart. If the composites were built to fail at the same pressures as metals, they would be very light indeed.

GW and others keep trying to use percentage calculations with lot of materials assumptions baked into them.

Assume for a moment that you had a steel with 500ksi tensile strength and stiffness on par with steel. A very thin piece of high strength steel will be exceptionally difficult to tear apart (with internal pressurization or external aero loads applied while it's pressurized), but bending it (to failure) is not that difficult. That is why you see external stiffeners or honeycomb sandwich core construction applied to the walls of composite propellant tanks, and why something 40% lighter than Aluminum is failing a pressure test at 277psi vs 82.7psi. If you only made it strong enough to fail at the same pressure, and instead devoted much more material to stiffness, then you understand what you actually must do, and why a composite tank will not burst or deform to failure, despite being "impossibly light".

Loading a propellant combo 68.8% heavier is no trouble at all compared to increasing tank volume by 54.5%, because the internal pressurization or external aero loads deforming the tank is what, structurally speaking, "kills" a composite with insufficient stiffness. The inter-ply stress from the weight increase of the propellant is not nearly enough to shear or delaminate the plies / tow. Demand that the same tank become 54.5% larger for equal or less weight, and then you have a serious stiffness and likely porosity problem. With RP1, I can increase the mass of the propellant tank by 1,345kg for equal weight and payload performance as the LH2 solution, but I certainly don't need to do that.

Total impulse and dry mass allocation is what counts for a SSTO. You either do or don't have enough Delta-V to reach orbit. Your composite tanks either do or don't have adequate stiffness to avoid deforming to failure, because strength is not an issue. Your engines either do or don't have adequate TWR. Solid core nuclear thermal has a 900s+ Isp, but you're never leaving the pad using one of those, so other properties clearly matter. LOX/LH2 is at the edge of feasibility. LOX/RP1 is much easier to do, despite being heavier.

kbd512 · 2024-05-29 16:34:41

To show you exactly what I'm doing for my Delta-V calculation, using initial and final masses, here is how I do it:

Maybe this is incorrect, but this is how I arrive at my numbers.

Ve = exhaust velocity
Isp = Specific Impulse, in seconds
g0 = gravitational constant
Ve = Isp * g0

mi = mass, initial
mf = mass, final

ΔV = Ve * ln(mi / mf)
ΔV = (Isp * g0) * ln(mi / mf)

For LOX/RP1 fed through a staged combustion engine, Isp(sl) =311s, Isp(vac) = 365s, Isp(avg) = 338s
ΔV = (338.3 * 9.80665) * ln(337,600 / 16,348)
ΔV = 3,317.589695 * ln(20.650844139955958)
ΔV = 3,317.589695 * 3.027756197019771
ΔV = 10,044.853m/s

Edit:
A 185km by 185km circular orbit implies a velocity of 7,793.23m/s.

That means I have 2,251.623m/s of excess ΔV to work with.
I presume my losses will be about 1,900m/s.
I have 351.623m/s of remaining ΔV to circularize the orbit.

That seems sufficient to me. If I'm still missing something, then anyone who knows what I'm missing, please feel free to point it out.

Last edited by kbd512 (2024-05-29 16:45:26)

kbd512 · 2024-05-29 17:46:44

Gravity (G) and Drag (D) and Total (T) Losses, in Meters per Second, by Launch Vehicle, for a 200km Circular Orbit, from Cape Canaveral*:

Launcher E-1 G: 1,586.2 D: 181 T: 1,767.2
SpaceX Falcon 9 FT / Block V G: 1,452.6 D: 79.5 T: 1,532.1
Saturn V G: 1572.7 D: 42.2 T: 1,614.9
Northrop-Grumman Pegasus G: 577.4 D: 150.8 T: 728.2

*Note:
Pegasus is an "all-solids" air-launched delta-winged rocket powered vehicle, which would normally fly out of Vandenberg, but flying out of Cape Canaveral results in negligible gravity and drag penalties. Polar orbits impose greater penalties.

Can anyone guess as to why air-launch looked so attractive to StratoLaunch Systems, relative to ground launch?

A 800m/s to 1,000m/s performance penalty is huge. If you want a more practical SSTO, a 1km/s penalty reduction is a big deal.

Launcher E-1 / Launcher Light uses LOX/RP1 staged combustion for the first stage.
Falcon 9 uses LOX/RP1 gas generator engines for the first stage and either a pressure-fed or staged combustion LOX/RP1 engine second stage.
Saturn V uses LOX/RP1 gas generator engines for the first stage and LOX/LH2 gas generator engines for the second stage- the only "mixed propulsion" vehicle on this list.

tahanson43206 · 2024-05-29 18:59:47

For kbd512 re #67...

I gave the post to ChatGPT4o, and it came back with an "all clear". I then asked it to evaluate the design as an SSTO and it noted the high mass ratio your calculations suggest.

Sure, I'll provide you with the bbcode-formatted documents for your forum post.
Document 1: Review and Confirmation of kbd512's Work
Review of kbd512's Delta-V Calculation
Delta-V Calculation Steps:
[]Specific Impulse (Isp): 338.3 s
[]Gravitational constant (g0): 9.80665 m/s²
[]Initial mass (mi): 337,600 kg
[]Final mass (mf): 16,348 kg
Step 1: Calculate exhaust velocity (Ve)
[]Ve = Isp * g0
[]Ve = 338.3 * 9.80665
Ve = 3,317.589695 m/s
Step 2: Calculate the natural logarithm of the mass ratio
[]ln(mi / mf) = ln(337,600 / 16,348)
[]ln(20.650844139955958) ≈ 3.027756197
Step 3: Calculate Delta-V
[]ΔV = Ve * ln(mi / mf)
[]ΔV = 3,317.589695 * 3.027756197
ΔV ≈ 10,044.853 m/s
Orbital Velocity and Remaining Delta-V:
[]Circular orbit velocity at 185 km altitude: 7,793.23 m/s
[]Excess Delta-V: 10,044.853 m/s - 7,793.23 m/s = 2,251.623 m/s
[]Presumed losses: 1,900 m/s
[]Remaining Delta-V for circularization: 2,251.623 m/s - 1,900 m/s = 351.623 m/s
Conclusion: kbd512's calculations are correct. The Delta-V required and the remaining Delta-V after accounting for losses are accurately computed. The remaining Delta-V of 351.623 m/s should be sufficient for circularizing the orbit.

and

Document 2: Observations About SSTO and Mass Ratio
Observations on SSTO Design and Mass Ratio
Key Indicators for SSTO:
[]Mass ratio (mi/mf): 337,600 / 16,348 ≈ 20.65
[]Specific Impulse (Isp): 338.3 s
[]Calculated Delta-V: 10,044.853 m/s
[]Required orbital velocity: 7,793.23 m/s
[]Presumed losses: 1,900 m/s
[]Remaining Delta-V for circularization: 351.623 m/s
SSTO Design Challenges:
[]Structural Efficiency: The structural mass fraction must be minimized to maximize propellant and payload mass.
[]Engine Performance: The engine must be efficient across a range of altitudes and speeds.
Material Constraints: Lightweight yet strong materials are required to withstand launch and reentry stresses.
Conclusion: The high mass ratio and sufficient Delta-V suggest that the design could theoretically be an SSTO. Practical implementation of an SSTO with such parameters is challenging and requires advanced engineering, materials, and engine technology. The parameters align with an SSTO design, but further validation through detailed design and engineering analysis is needed to confirm feasibility.

(th)

tahanson43206 · 2024-05-29 19:12:59

For kbd512 ... I asked about the X-37b, and learned that it has an on-orbit mass of about 5 tons.

I think ChatGPT4o has pointed out the challenge you appear to be taking on.

I note that GW Johnson came up with 13 tons on orbit using LH2/LOX for RGClark's 200 ton vessel, and lesser tonnage for less capable propellants.

Previously, when I asked ChatGPT4o for a conceptual launcher with 200 tons of propellant at launch, it came up with 25 tons on orbit, but I suspect it's choice of exhaust velocity was on the optimistic side.

Do you happen to know the mass of the US X-37b space plane on orbit? It is launched by a traditional two stage chemical rocket, but I am wondering if the mass is comparable to the 16 tons envisioned by kbd512.
ChatGPT
Yes, the X-37B space plane, developed by the United States, has a significantly lower mass compared to the 16 tons (16,348 kg) envisioned by kbd512. Here are the relevant details:
The X-37B has an approximate launch mass of 4,990 kg (4.99 tons).
This mass includes the spacecraft itself and any payload it carries into orbit.
It is launched into space aboard an Atlas V or Falcon 9 rocket, which are both traditional two-stage chemical rockets.
Given this comparison, the X-37B is much lighter than the 16-ton vehicle described by kbd512. The difference in mass highlights the substantial challenge of achieving Single Stage to Orbit (SSTO) capability with a vehicle as heavy as the one kbd512 is proposing. The X-37B's use of a multi-stage launch system is a more conventional approach, leveraging the efficiency gains provided by staging to reach orbit.

I'm focused on the X-37b because it is a fully reusable space plane.

(th)

tahanson43206 · 2024-05-30 18:51:27

For kbd512 re SSTO forum....

SpaceNut has given you an entire forum to work with....

You've created a topic about costs, and it turns out you didn't mean all SSTO ideas that might come along.

Instead, it appears you want the topic you created to focus on one particular design.

Please change the title to more accurately reflect what you want the topic to be about.

***
I am confident ChatGPT4o would be willing to look at your design for a 500 passenger SSTO, but if you've created one I've missed it.

Please put the link into housekeeping, where i'll be sure to find it.

All I know for an absolute fact is that you created a design for a 337.6 ton vehicle that has the ability to put 16 tons into orbit.

The specification did not indicate the kind of fuel it would burn, so naturally ChatGPT4o used the highest energy fuel that is available.

If you want to create a topic about a different 337.6 ton vehicle that burns a specific fuel, that would be interesting.

I understand the tradeoff you are evaluating, between energy of the fuel and the mass of the tank. If you had a mathematician who could do calculus, you might be able to find the answer to the question of which approach is best.

A Python program might be able to perform the calculations needed to try all the possible solutions.

Whatever you do in this adventure you're on, there will be NewMars readers who (I'm pretty sure) will be interested in following along.

(th)

SpaceNut · 2024-05-30 19:11:41

The cost is not just materials as you are also talking about the sale of seats which are different than operations costs and even different to assembly or manufacturing costs of the plant that makes the parts.

Rockets costs will vary depending on fuel and oxidizer, it increases not only due to density of them but the thickness of materials to hold them as well as how tall the rocket will be with the engines that can use that fuel.
Change the fuel and engine changes how tall and mass of parts that are used to hold the fuel just as much.

tahanson43206 · 2024-05-31 14:06:41

For kbd512 re recent work....

it is good to see your high energy level and productivity in the early stages of the 500 passenger vehicle conceptualization.

500 Passenger SSTO Design Concept seems to be well under way.

I'll step back and watch as it develops in what I hope is a step-by-step progression.

***
FYI ... GW has verified your notional 337.6 ton vehicle, after I convinced him to run the numbers even though we all know it is a fantasy intended to stimulate thought in the minds of readers.

It is good to see Calliban thinking about the vertical launch device. In case you miss his question about level of G for the first boost, I am intrigued by the question of whether your planned webbing bunks would be able to hold the passengers through Calliban's 10 G option. It might be possible but I'm not sure about the passengers. That leads to the question of how many g's your passengers would experience, so I hope you find time to look into that.

Best wishes for continued success as you develop these ideas!

(th)

tahanson43206 · 2024-06-02 10:04:17

For kbd512 re Calliban's offer....

Please keep the exhaust in mind ...

Elon had to add water deluge for his fixed launch tower.

The launch complex the two of you will be designing will need to somehow deal with the exhaust.

Where you are in the launch sequence when you light the engines will make a difference.

Best wishes for continued success with this initiative.

(th)

kbd512 · 2024-06-02 14:56:16

tahanson43206,

A water deluge system is pretty close to a hard requirement for all large vertical launch vehicles. I had thought that the idea was to provide horizontal velocity of 300m/s, because that is what will reduce gravity losses the most, which dominate the losses category over aerodynamic drag. If there's nothing behind the vehicle for a mile or so, then no water deluge system is required for a horizontal launch. It might kick up a dust cloud, but it's not directed at the ground. If there will be structures or other obstacles behind it, then a water deluge system is still required. All these operational issues should be put into a list and ranked in order of importance or impact on the mission.

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