Airbreathing SSTO Design

[Spacescifi]

It seems to me that SSTOs only make sense if they are airbreathing.

The challenge is that airbreating SSTOs must fly longer in the atmosphere and experience more friction and heat doing so. SSTOs don't need to take off like airplanes, but they are easier to make that way.

A wider forward profile will grant wider intakes which will provide more air 'propellant' to mix with with your nuclear power, but it will also increase drag.

So what you need for an efficient SSTO is a lightweight but strong ship with a wide forward profile to scoop a lot of air. Some variant of a saucer or even linked saucers could work, since you obviously want payload/crew separate from engines.

What are your thoughts on this design?

[K^2]

At low speeds, you don't need to scoop a lot of air, because you don't need a lot of thrust. Once you get going, you don't need a big scoop, because you'll be collecting enough air as is. Take a look at intakes on SR-17 and compare them to intakes on a commercial jet. Even if you're planning to compress and store collected air to use as oxidizer at high altitude, like on SABRE engine, you still don't need huge scoops.

So for what an SSTO like that might look like, I would look at Skylon, since it's pretty much exactly what you're describing in principle. They use chemical fuel, rather than NTR, but that doesn't actually make nearly as much difference as you might think it does. Most of the propellant weight of conventional rocket is in oxidizer, not fuel, and air-breathing NTR won't give you a lot of I_SP advantage over LH2. A lot of I_SP advantage of NERVA, for example, comes from using a very light propellant, hydrogen gas, which you sacrifice when switching to much heavier air mixture. If anything, I suspect air-breathing NTR will be closer to I_SP of a kerlox rocket.

So yeah, an air-breathing NTR SSTO seems plausible in principle, and I would expect it to look mostly similar to Skylon. And given that Russians are believed to be developing air-breathing NTR cruise missiles, we probably even have the tech to build something like this, but various treaties prevent anyone from turning it into actual orbital capability.

[Spacescifi]

30 minutes ago, K^2 said:

At low speeds, you don't need to scoop a lot of air, because you don't need a lot of thrust. Once you get going, you don't need a big scoop, because you'll be collecting enough air as is. Take a look at intakes on SR-17 and compare them to intakes on a commercial jet. Even if you're planning to compress and store collected air to use as oxidizer at high altitude, like on SABRE engine, you still don't need huge scoops.

So for what an SSTO like that might look like, I would look at Skylon, since it's pretty much exactly what you're describing in principle. They use chemical fuel, rather than NTR, but that doesn't actually make nearly as much difference as you might think it does. Most of the propellant weight of conventional rocket is in oxidizer, not fuel, and air-breathing NTR won't give you a lot of I_SP advantage over LH2. A lot of I_SP advantage of NERVA, for example, comes from using a very light propellant, hydrogen gas, which you sacrifice when switching to much heavier air mixture. If anything, I suspect air-breathing NTR will be closer to I_SP of a kerlox rocket.

So yeah, an air-breathing NTR SSTO seems plausible in principle, and I would expect it to look mostly similar to Skylon. And given that Russians are believed to be developing air-breathing NTR cruise missiles, we probably even have the tech to build something like this, but various treaties prevent anyone from turning it into actual orbital capability.

 

I really do think you do need a lot of thrust if you are doing what I want...namely horizontal takeoff using only nuclear power with airbreathing. Having smaller intakes from dead stop won't help.

Neither the Skylon nor the SR-71 do that. It has never been done that I know of.

Using only known physics and science, SSTOs just expand our transit to orbit and back capability.

If anything, reentry is the biggest issue of all. Remember how much work the reusuable space shuttle needed after each reentry?

Without ablative tiles or propellant sweating of the hull, the craft wll take definite hull damage during each reentry.

It cannot do that or it must be minimal to be a true reusable SSTO.

Edited November 1, 2020 by Spacescifi

[K^2]

37 minutes ago, Spacescifi said:

horizontal takeoff using only nuclear power with airbreathing. Having smaller intakes from dead stop won't help.

That's been a solved problem since the first jets. Nothing about using NTR makes this conceptually different from a jet engine. If you want an air-breathing engine operating at low speeds, you need a compressor. You'll spin the compressor up with electric motor on the ground. Once you have it going, you can run exhaust past the turbine to keep the compressor running. That's every single turbojet out there. And switching to a ram mode is also a solved problem. See aforementioned SR-17.

Don't think of NTR as something special. From perspective of building a propulsion system, it doesn't matter how you get heat into the working fluid. You can burn fuel or you can use a heat exchanger with a nuclear reactor. The effect is identical. And the way you force working fluid into the combustion chamber or heat exchanger is also the same. If you have an NTR running from on-board propellant, like NERVA, you must pressurize the tank or use pumps to get propellant into heat exchanger. If you are running an air-breather, then the working fluid is air, and you force it into combustion chamber or heat exchanger by using compressor or a ram scoop. The rest of the physics is identical. You don't need a larger scoop for NTR turbojet or a scram jet than you would with conventional, kerosene-burning turbojet or a scram jet. Depending on what kind of reactor cycle you're going with, even the dimensions of the engine might end up very similar, with the reactor core located external to the engines.

There are additional challenges to building NTR equivalent of a scram jet, because it's difficult to organize heat exchange with supersonic flow, but you either get that problem solved or you don't. Larger scoop is just going to generate more drag, and if you can't produce thrust to counter drag of a small scoop, making scoop larger isn't going to help.

[Guest]

6 hours ago, Spacescifi said:

If anything, reentry is the biggest issue of all. Remember how much work the reusuable space shuttle needed after each reentry?

With ~9000 m/s to achieve low earth orbit reentry isn't really what's stopping the concept

Edited November 1, 2020 by Guest

[wumpus]

First place I would look at is the X-43, an airbreather that managed to maintain in excess of 2,300m/s (it did rather well accelerating around 1000m/s, but that was a different flight and likely a different configuration.

The idea that you could shield a nuclear reactor and get the whole thing to weigh significantly less than the liquid hydrogen needed to get to LEO is extremely unlikely.  The kicker is that for a fuel powered rocket, you get similar thrust the entire flight, but your mass steadily decreases through the flight.  The mass of the reactor would stay the same.

There was a proposal for a nuclear bomber (and I'd suspect a Soviet program as well that I've never heard of) during the 1950s or so.  I don't think that it is remotely possible for it to get into space.

Your obsession with SSTO simply doesn't work well with "known physics".  If you really want to understand the rocket equation, not only is KSP a great way to learn it, but it is on sale 75% off ($10)  (until Monday, November 1, 2020.  Probably noonish EST).

[Spacescifi]

1 hour ago, wumpus said:

First place I would look at is the X-43, an airbreather that managed to maintain in excess of 2,300m/s (it did rather well accelerating around 1000m/s, but that was a different flight and likely a different configuration.

The idea that you could shield a nuclear reactor and get the whole thing to weigh significantly less than the liquid hydrogen needed to get to LEO is extremely unlikely.  The kicker is that for a fuel powered rocket, you get similar thrust the entire flight, but your mass steadily decreases through the flight.  The mass of the reactor would stay the same.

There was a proposal for a nuclear bomber (and I'd suspect a Soviet program as well that I've never heard of) during the 1950s or so.  I don't think that it is remotely possible for it to get into space.

Your obsession with SSTO simply doesn't work well with "known physics".  If you really want to understand the rocket equation, not only is KSP a great way to learn it, but it is on sale 75% off ($10)  (until Monday, November 1, 2020.  Probably noonish EST).

 

Hmmm....maybe if the SSTO's hull and engine is precooled? Like with a cold gel adhesive for the outet hull?  It will likely vape away but the sooner it reaches orbit the better the precooling will be effective.

As for weight, if nuclear reactors could be made smaller then the weight would reduce. As for shielding, all you really need is material with a high hydrogen content to catch the gammas, and lead. Both of which are...yeah...heavy.

 

I guess your point is that the way we go to space is the best way we know of.

In order to make SSTOs effective using known physics, we need to make extremely precooled vessels.

Perhaps so cold they float off super conductors like magnets, and then take off vaping as they go?

Also lightweight materials that could absorb more radiation or at least reflect it would be needed.

So yeah....not current tech.

The only thing we can do right now is dip an SSTO in super cold liquid nitrogen or perhaps LH and then take off as fast as possible?

Perhaps boost it with a rocket sled for take off? Which is well within current tech too.

Edited November 1, 2020 by Spacescifi

[kerbiloid]

6 minutes ago, Spacescifi said:

material with a high hydrogen content to catch the gammas

Hydrogen is bad gamma catcher. High atomic number and density rule.

Say, golden coins. Anyway the other part will cost more.

The lead is much poorer shielding than the gold, too. (density 11.3 vs 19)

Edited November 1, 2020 by kerbiloid

[Spacescifi]

3 minutes ago, kerbiloid said:

Hydrogen is bad gamma catcher. High atomic number and density rule.

Say, golden coins. Anyway the other part will cost more.

The lead is much poorer shielding, too.

 

Google:

shield need to be about 13.8 feet of water, about 6.6 feet of concrete, or about 1.3 feet of lead. Thick, dense shielding is necessary to protect against gamma rays. The higher the energy of thegamma ray, the thicker the shield must be. X-rays pose a similar challenge.

NuclearConnect.org › ... › Science

Protecting Against Exposure - ANS - Nuclear Connect

[kerbiloid]

13 minutes ago, Spacescifi said:

extremely precooled vessels.

Perhaps so cold they float off magnetuc surfaces as a superconductor, and then take off vaping as they go?

With sleds. To slide on the frozen atmospheric water (aka snow).

4 minutes ago, Spacescifi said:

Google:

shield need to be about 13.8 feet of water, about 6.6 feet of concrete, or about 1.3 feet of lead. Thick, dense shielding is necessary to protect against gamma rays. The higher the energy of thegamma ray, the thicker the shield must be. X-rays pose a similar challenge.

Yes, you need 10 times thicker layer of water (btw, it's H2O, not H2, with density 1000) than of lead, and you need twice as thin layer of gold.

The pure hydrogen would be about 1000/80*13.8 ~170 ft.

15 minutes ago, Spacescifi said:

super cold liquid nitrogen

ALmost as cold as liquid oxygen and methane.

Edited November 1, 2020 by kerbiloid

[Spica]

Cooling is a minor problem for SSTOs, since they're required to be super bulky to fit all the hydrogen fuel needed to reach orbit. That large volume comes along with a large surface area which makes re-entry heating much milder. Lower ballistic coefficients allow the bulk of atmospheric braking to happen at higher altitudes, trading a large reduction in heating intensity for a greater heating duration.

The real problem with SSTOs is, and I can not stress this enough, structural weight. Nuclear powered air-breathing SSTOs suffer doubly from excess weight, since they need to carry heavy air-breathing engines, wings, excess structure to support multiple load paths, and heavy reactors and their requisite shielding. Additionally any NTR powered SSTO will almost certainly use hydrogen propellant, which will invariably make the structure even larger and heavier due to its extremely low density.

[Spacescifi]

18 minutes ago, Spica said:

Cooling is a minor problem for SSTOs, since they're required to be super bulky to fit all the hydrogen fuel needed to reach orbit. That large volume comes along with a large surface area which makes re-entry heating much milder. Lower ballistic coefficients allow the bulk of atmospheric braking to happen at higher altitudes, trading a large reduction in heating intensity for a greater heating duration.

The real problem with SSTOs is, and I can not stress this enough, structural weight. Nuclear powered air-breathing SSTOs suffer doubly from excess weight, since they need to carry heavy air-breathing engines, wings, excess structure to support multiple load paths, and heavy reactors and their requisite shielding. Additionally any NTR powered SSTO will almost certainly use hydrogen propellant, which will invariably make the structure even larger and heavier due to its extremely low density.

I see.

 

Perhaps then instead nuclear power is better used simply as lasers to heat up ship hulls as the ship ascends to orbit?

Nuclear powered ground based lasers.

That way you get the best of both worlds...the lessening of weight as propellant is expended and the power of nuclear energetic heat added to the engine's efficiency and thrust.

 

Nothing physics wrong with this idea...politcally yes 

 

But in a scifi setting where a planet's populace is not pointing nukes at each other then they won't feel threatened by pointing lasers at launched spacecraft. They just need to avoid lasing  orbiting satelites.

Edited November 1, 2020 by Spacescifi

[Spacescifi]

38 minutes ago, kerbiloid said:

With sleds. To slide on the frozen atmospheric water (aka snow).

Yes, you need 10 times thicker layer of water (btw, it's H2O, not H2, with density 1000) than of lead, and you need twice as thin layer of gold.

The pure hydrogen would be about 1000/80*13.8 ~170 ft.

ALmost as cold as liquid oxygen and methane.

 

Liquid helium is coldest according to google.

[SOXBLOX]

1 hour ago, Spacescifi said:

But in a scifi setting where a planet's populace is not pointing nukes at each other then they won't feel threatened by pointing lasers at launched spacecraft. They just need to avoid lasing  orbiting satelites.

"We do not mistrust each other because we are armed; we are armed because we mistrust each other."

1 hour ago, Spacescifi said:

Liquid helium is coldest according to google.

And good luck using it.

11 hours ago, K^2 said:

Don't think of NTR as something special. From perspective of building a propulsion system, it doesn't matter how you get heat into the working fluid. You can burn fuel or you can use a heat exchanger with a nuclear reactor. The effect is identical. 

Exactly this. This confused me when I first read about nuclear engines, until I realized that all a reaction engine is is a way to spit hot gas in one direction.

[wumpus]

4 hours ago, Spacescifi said:

 

Google:

shield need to be about 13.8 feet of water, about 6.6 feet of concrete, or about 1.3 feet of lead. Thick, dense shielding is necessary to protect against gamma rays. The higher the energy of thegamma ray, the thicker the shield must be. X-rays pose a similar challenge.

NuclearConnect.org › ... › Science

Protecting Against Exposure - ANS - Nuclear Connect

So if you are using water you get 2m long, and we'll assume a 2m diameter rocket (width of a 737-200 fuselage that showed up from googling), so 6.28 cubit meters of shielding or 6.3 tonnes.  Since shielding is mainly all about mass, I'd simply use that mass even if you use lead or depleted uranium.  And how much will this reactor mass?  And just how are you planning to go from zero to supersonic (and how much will that mass?).  All those tonnes add up, and need to be sent to LEO.  But the fuel an airbreather burns only has to be accelerated until burned.

[JadeOfMaar]

Two very important reasons why air-breathing/spaceplane SSTO can't be done yet are:

1. Producing hull materials that can survive shock heating at speeds over Mach 3. The X-15 rocketplane and X-33 VTHL easily come to mind. Carbon fibre and ALON transparent ceramic are the best materials I'm aware of, but who knows how well they've been tested.
2. Scramjet tech hasn't developed much, and might be on the backburner (thanks to Skylon precooler testing making progress) as far as John Public gets to know. The core of the scramjet problem is how to keep the pilot light/ flame holder from being yoinked when supersonic air is rushing by it in the combustion chamber.

 

[Spacescifi]

1 hour ago, JadeOfMaar said:

Two very important reasons why air-breathing/spaceplane SSTO can't be done yet are:

1. Producing hull materials that can survive shock heating at speeds over Mach 3. The X-15 rocketplane and X-33 VTHL easily come to mind. Carbon fibre and ALON transparent ceramic are the best materials I'm aware of, but who knows how well they've been tested.
2. Scramjet tech hasn't developed much, and might be on the backburner (thanks to Skylon precooler testing making progress) as far as John Public gets to know. The core of the scramjet problem is how to keep the pilot light/ flame holder from being yoinked when supersonic air is rushing by it in the combustion chamber.

 

Well...the goverments know already what is and is not currently possible.

If I had the money I would try and see if magnetizing the air was possible with supersonic airflow. It should be easy to convert it into plasma if nothing else, and plasma we know can be diverted with magnetic fields.

Also (google it if you wish), researchers say they have managed to magnetize regular unmodified air by messing around with lasers in a specific circular configuration.

There is no real need for any of it that justifies the expense, but I kind of assume in a scifi setting that many current 'expensive' technologies would be cheap in a far future setting.

 

 

Edited November 2, 2020 by Spacescifi

[JadeOfMaar]

@Spacescifi I know of a plausible concept for using an EM field (potentially, effectively polarizing the hull) to repel reentry plasma. The subjects I know of that correlate are MagnetoHydroDymanics and Electromagnetic TCS.

In a sci-fi setting, I would be quite confident that for hulls: the material heat tolerance problem would be solved, or EM-TCS would be very effective and common-place, and for hypersonic propulsion: scramjets would be replaced by a fully matured form of the trending prototype microwave air-breathing plasma thruster, which in turn would be complemented with (if I may go there) Methallic Hydrogen + (LH2 or Water) bipropellant rockets.

[Spacescifi]

42 minutes ago, JadeOfMaar said:

@Spacescifi I know of a plausible concept for using an EM field (potentially, effectively polarizing the hull) to repel reentry plasma. The subjects I know of that correlate are MagnetoHydroDymanics and Electromagnetic TCS.

In a sci-fi setting, I would be quite confident that for hulls: the material heat tolerance problem would be solved, or EM-TCS would be very effective and common-place, and for hypersonic propulsion: scramjets would be replaced by a fully matured form of the trending prototype microwave air-breathing plasma thruster, which in turn would be complemented with (if I may go there) Methallic Hydrogen + (LH2 or Water) bipropellant rockets.

 

Oh no you didn't!

You cannot say that word! LOL!

The heat tolerance is big deal. That is why in a prior thread I suggested cooling stuff till the atoms stop moving. But why stop there?

I would cool an SSTO's hull to a zillion degrees in the negative if that means I can ascend to orbit under MY OWN power and thrust using low propellant reserves.

Consequences? Before launch. Do not. Touch. The hull. Will freeze your hand solid.

To get the vessel that cold it will likely involve a vacuum chamber, cool temperatures, and electromagnetic shenanigans (inasmuch that is what the IRL experiment took).

So this sort of SSTO could take off once under it's own power, then land, go into the cooling chamber, and do it all over again.

 

The scifi dream is a vessel that can use air and electric or nuclear power to scramjet into orbit WITH lots of propellant. 

Basically using propellant for space, and thermal energy with air for launch and landing.

Reentry would actually help. Dive into the plasma friction and engage the engines, fly down and loop back up before going horizontal again, and finally lose speed by manuvering and land using propellant rocketry...ideally on a world with refueling opportunities near the landing site.

Edited November 2, 2020 by Spacescifi

[JadeOfMaar]

Heheh. ;D Yep I went there.

There's a major problem with the idea of "cooling the hull to absolute zero" ...

Quote

I suggested cooling stuff till the atoms stop moving.

I don't need to tell you that you really, really, don't want your atoms to stop moving.

You invoke an exceptionally huge requirement for cryogenic material and a cryogenic chamber to expose the craft to, and you introduce the parallel, extreme dangers of: making the hull brittle and worthless in the moment that you're flash-cooling it to such a degree; making the hull brittle by exposing it to the utterly extreme temperature gradient between touching absolute zero and burning in hypersonic flame (assuming the hull even stays cold enough by then that the cooling efforts matter). Moving parts and their fluids would very quickly crumble or shatter as their chemical behaviors change along with the state of matter. Pressurized parts might shatter and implode or explode because the air or propellant inside them would turn solid and possibly cause vacuum pressure that they weren't designed to handle.

There are proposals for sweating cryogenic propellant to dampen reentry heat. Methane has been proposed at some point by SpaceX in order to help Starship's survivability on reentry. To carry enough of a cryogenic substance that isn't propellant is to carry dead mass

The microwave air plasma thruster in concept meets the demand for both a scramjet and a viable electric or nuclear jet engine. Once that's made up, classical scramjets and possibly nuclear turbojets would become relics. You could tank the air for a microwave jet and have the liberty to ascend more steeply because you don't need enough intake ram effect to fill a pressure vessel as you would need to: super-heat the air so it readily ignited when it reaches the scramjet's candle and fuel injectors; and to maintain enough intake air pressure to keep scramjet combustion stable and thrust production sufficient. We're also now quickly moving along with battery density tech which is critical to having the electrical systems to power electric engines or EM heatshields. If compact fusion power happens, the demand for fission reactors may drop quite quickly.

All that said, I more enjoy using LF-burning scramjets in KSP than the idea of using "a rocket that consumes mainly/only air."

[Nuke]

i figure the best nuclear engines for space travel would be ones designed to operate on a  wide variety of propellants. so long as you can tank up enough delta-v to get to your next destination you are fine.  you might be running at a sub-optimal isp most of the time, but if it gets you where you are going then it becomes irrelevant.

staying with chemical propulsion around earth is probably a good idea. the reactor is better off on the ground making fuel. skylon type craft handle the ferrying of cargo and personnel to orbit where an efficient space tug or freighter (which may be nuclear powered) takes over the rest.  skylon's use of a standard payload container means you can load up a large unmanned freighter in orbit with several skylon launches (including a few tankers), and send it on a long efficient crawl to mars or whatever.  ships for moving humans around would be barebones and have higher thrust , lower isp for time optimized transfers (as opposed to fuel optimized). if you would want to build a mars base, you send a fully laden freighter ahead of the transport (they arrive around the same time though) and then manned operations can commence.

later on as the system becomes colonized its better to have specialized surface to orbit vehicles at every destination. 

Edited November 2, 2020 by Nuke

[Spacescifi]

On 11/1/2020 at 9:28 AM, wumpus said:

First place I would look at is the X-43, an airbreather that managed to maintain in excess of 2,300m/s (it did rather well accelerating around 1000m/s, but that was a different flight and likely a different configuration.

The idea that you could shield a nuclear reactor and get the whole thing to weigh significantly less than the liquid hydrogen needed to get to LEO is extremely unlikely.  The kicker is that for a fuel powered rocket, you get similar thrust the entire flight, but your mass steadily decreases through the flight.  The mass of the reactor would stay the same.

There was a proposal for a nuclear bomber (and I'd suspect a Soviet program as well that I've never heard of) during the 1950s or so.  I don't think that it is remotely possible for it to get into space.

Your obsession with SSTO simply doesn't work well with "known physics".  If you really want to understand the rocket equation, not only is KSP a great way to learn it, but it is on sale 75% off ($10)  (until Monday, November 1, 2020.  Probably noonish EST).

 

My 'obsession' with SSTOs is likely spawned originally from watching the millennium falcon take off to space as a child, not realizing at the time what space travel involved IRL.

Once I learned later real physics I only wanted to see if it were possible. It is not...at least if you want a meaningful payload.

Currently my 'obsession' with SSTOs has likely a lot more to do with the fact that I play Oolite...a many times over modded clone of the original elite.

It made me dream of writing a universe where civilians can own tramp freighters and make a living shipping and trading goods across the galaxy.

 

Of course, my writing would be diffetent from the oolite verse in several respects, but I do have a fondness for the concept of having your own spaceship and doing WHATEVER you like with it...rather than being tied to any specific job per se.

 

In Oolite I fly a Python that has a max payload of 100 tons. My cargo bays are usually very empty unless I resort to pirating.

I make my money merely from doing tournaments at advanced tech feudal systems. Which can net over 10,000 credits in a single match max. That's how I was able to afford my Python relatively quickly.

Currently I am in galaxy two, trying to upgrade to a vessel with even more cargo space so I can wipe out Thargoids more effectively. The Thargoid Wars OXP makes them attack more often.

I don't play fair anymore than the game does (1v6? Come on!). I simply buy as many light fighters as possible and let them lase everything by a thousand tiny cuts before I slowly fly in and deal the final blows.

 

Edited November 3, 2020 by Spacescifi

[Hannu2]

On 11/2/2020 at 2:00 AM, Spacescifi said:

If I had the money I would try and see if magnetizing the air was possible with supersonic airflow. It should be easy to convert it into plasma if nothing else, and plasma we know can be diverted with magnetic fields.

You do not need money but just some time to learn basics of physics and see that you can not buy such magnets with any amount of money. No one knows how to do such magnets so that they can be fitted in spaceship. Any known material or any imaginable combinations of known elements (their bonding follow certain natural laws and it can be predicted that order of magnitude improvements in material properties will not happen) can not be used.

If you check those superconducting behemoth monsters used for example in particle accelerators, it may be hard to imagine such as part of spacecraft. And their field may not be nearly enough. As far as I know needed field strength is enormous.

[Hannu2]

On 11/1/2020 at 9:02 PM, Spacescifi said:

The only thing we can do right now is dip an SSTO in super cold liquid nitrogen or perhaps LH and then take off as fast as possible?

Energy of heating is much higher than any reasonable thermal capacity. At least in atmospheric entry. Heat must be radiated out or absorbed in some kind of ablative or vaporizing system.

On 11/1/2020 at 9:02 PM, Spacescifi said:

Perhaps boost it with a rocket sled for take off? Which is well within current tech too.

Or what if complex sled and expensive and potentially very unsafe railing and suspension systems was replaced with a freely flying rocket stage which would kick SSTO above thick atmosphere and give some initial velocity. That kicker stage could left some fuel and return to launch site. Or maybe even land to a special ship on ocean and save some DV.

[wumpus]

10 hours ago, Spacescifi said:

 

My 'obsession' with SSTOs is likely spawned originally from watching the millennium falcon take off to space as a child, not realizing at the time what space travel involved IRL.

Once I learned later real physics I only wanted to see if it were possible. It is not...at least if you want a meaningful payload.

Currently my 'obsession' with SSTOs has likely a lot more to do with the fact that I play Oolite...a many times over modded clone of the original elite.

It made me dream of writing a universe where civilians can own tramp freighters and make a living shipping and trading goods across the galaxy.

 

Of course, my writing would be diffetent from the oolite verse in several respects, but I do have a fondness for the concept of having your own spaceship and doing WHATEVER you like with it...rather than being tied to any specific job per se.

 

In Oolite I fly a Python that has a max payload of 100 tons. My cargo bays are usually very empty unless I resort to pirating.

I make my money merely from doing tournaments at advanced tech feudal systems. Which can net over 10,000 credits in a single match max. That's how I was able to afford my Python relatively quickly.

Currently I am in galaxy two, trying to upgrade to a vessel with even more cargo space so I can wipe out Thargoids more effectively. The Thargoid Wars OXP makes them attack more often.

I don't play fair anymore than the game does (1v6? Come on!). I simply buy as many light fighters as possible and let them lase everything by a thousand tiny cuts before I slowly fly in and deal the final blows.

 

The fact that I watched a lot of Superman as a kid doesn't mean I expect physics to allow human flight via a cape.  Same with SSTO.  Air breathing is probably the only way to go, but don't bother adding nuclear or antimatter  to it.