ESA ATL Plausibility Checks and Development

[Bahamut-255]

ESA Post-Europa Launch Vehicle

A/N: Sorry for the delay everyone, but real life has a habit of doing that to you. But I'm ready to add a new segment here now.

Anyways. I think I've sorted out the Manned Spacecraft that TTL ESA will be using for a good 20+ years, which I think I'll be naming Solaris - thanks for the suggestion Archibald . So now I can turn attention to the Launch Vehicle that's going to be putting it into orbit in the first place. For this, I'm looking at making 10,000Kg to a 225 x 225 Km LEO at 51.6 degrees inclination the base payload for Manned Flight.

Now I've selected a simple TSTO design that can send a manned payload into such an orbit using only LOX/Kerosene propellants - if only just, and about 11,000Kg of unmanned payload to the same orbit - in it's base form. And while the 2nd stage engines should be fairly simple for ESA to build, I suspect that the much more powerful 1st stage engines will be the pacing item. So assuming a start date of around 1980, having it ready by 1988 or thereabouts seems plausible - the same development time as for the OTL Ariane 5.

Next are the performance upgrade options, where there is a lot to play with. My personal preferance is the Common Core Booster (CCB) system where another pair of 1st stages flank the 1st stage for the ultimate performance augmentation of the family, with a series of smaller solid and liquid rocket boosters to fill the interim payload options. Since greater payload capability is what the whole launch vehicle is about - on top of Manned Spaceflight Capability - it makes perfect sense to pre-design it to handle the extra loads right from the outset. LOX/LH2 upper stages will feature as well, for the MEO, HEO, GTO, TLI, TMI, TVI & TJI flights.

The final note for the time being. ESA Manned flights to Mir Space Station. I have every intention of making this happen since I plan on having it all ready by no later than the early 1990s.

All I need now is a name for the new family of launch vehicles. Suggestions anyone?

 

[e of pi]

A/N: Sorry for the delay everyone, but real life has a habit of doing that to you. But I'm ready to add a new segment here now.

Anyways. I think I've sorted out the Manned Spacecraft that TTL ESA will be using for a good 20+ years, which I think I'll be naming Solaris - thanks for the suggestion Archibald . So now I can turn attention to the Launch Vehicle that's going to be putting it into orbit in the first place. For this, I'm looking at making 10,000Kg to a 225 x 225 Km LEO at 51.6 degrees inclination the base payload for Manned Flight.

This seems like a reasonable payload for a manned capsule. The inclination means either a heck of a dogleg during ascent or a day or two spent in transfer orbits. Both are possible, but keep those in mind as constraints on your spacecraft design.

Now I've selected a simple TSTO design that can send a manned payload into such an orbit using only LOX/Kerosene propellants - if only just, and about 11,000Kg of unmanned payload to the same orbit - in it's base form. And while the 2nd stage engines should be fairly simple for ESA to build, I suspect that the much more powerful 1st stage engines will be the pacing item.

Any LOX/Kero engine will be a pacing item as far as I know. The Ariane core was hypergolic, the only high-energy engines they had at all were LOX/LH2 upper stagers like the HM7B which first flew in '79 and has been in use since. I'd think they'd look to keep that, though I guess they might pursue a new first stage engine. Why spend tons of time in development for a worse engine? I'm also skeptical that ESA would go kerolox--the French were really big on hydrolox, and that gave them a lot of influence. After the UK dropped out, European launch has basically been a French party. Even if they do go kerolox, I'm not sure where they'd start for an engine--they'd almost need to buy from Russia or the US (and if it were me, I'd go Russian). On the other hand, at the point where you're already resigned to buying foreign engines, perhaps they give into the allure of American hydrolox? You could use the STME originally intended for the cancelled American ALS, Rocketdyne Just in the meantime, of course, while they develope a sufficiently capable engine of their own.

So assuming a start date of around 1980, having it ready by 1988 or thereabouts seems plausible - the same development time as for the OTL Ariane 5.

I hate to point this out, but you have the program start date confused with the first flight. Ariane 5 began development in '88, and first flew in '96. If you want it to start in 1980, you'll need to mess around a lot with ESA--they were still doing all they could to wring performance out of the basic Ariane.

Next are the performance upgrade options, where there is a lot to play with. My personal preferance is the Common Core Booster (CCB) system where another pair of 1st stages flank the 1st stage for the ultimate performance augmentation of the family, with a series of smaller solid and liquid rocket boosters to fill the interim payload options. Since greater payload capability is what the whole launch vehicle is about - on top of Manned Spaceflight Capability - it makes perfect sense to pre-design it to handle the extra loads right from the outset.

In that case, you'd almost need to design the core for solids and CCB up front, not in the future. Intended loads, mounting points, all that. If you're going to do it, why wait? Spend the money up front and do it right the first time.

LOX/LH2 upper stages will feature as well, for the MEO, HEO, GTO, TLI, TMI, TVI & TJI flights.

As I said, the upper stage will almost assuredly be hydrolox from the start--the French have historically liked hydrolox, and they already had good engines for it, whereas they didn't have good kerolox technologies. They'd need to give the HM7B restart, but that's a lot cheaper than developing an entire new engine using entirely different fuels.

The final note for the time being. ESA Manned flights to Mir Space Station. I have every intention of making this happen since I plan on having it all ready by no later than the early 1990s.

As I mentioned above, you've got the development timeline wrong. If it starts when OTL Ariane 5 did, then it's not going to be ready for flight testing until the early-to-mid 90s. You'd still be able to maybe do a flight or two to Mir, but it'll be in the decrepit years. Additionally, European launch capability on this order may have already had some butterflies on the Russian and American programs--though how much depends on whether you're going to stick to your 1980 date or the OTL Ariane 5 start of 1988.

All I need now is a name for the new family of launch vehicles. Suggestions anyone?

It's a new French launch vehicle. Ariane 5 is almost inevitable. Sometimes we engineers can be incredibly dull.

 

[Bahamut-255]

This seems like a reasonable payload for a manned capsule. The inclination means either a heck of a dogleg during ascent or a day or two spent in transfer orbits. Both are possible, but keep those in mind as constraints on your spacecraft design.

Any LOX/Kero engine will be a pacing item as far as I know. The Ariane core was hypergolic, the only high-energy engines they had at all were LOX/LH2 upper stagers like the HM7B which first flew in '79 and has been in use since. I'd think they'd look to keep that, though I guess they might pursue a new first stage engine. Why spend tons of time in development for a worse engine? I'm also skeptical that ESA would go kerolox--the French were really big on hydrolox, and that gave them a lot of influence. After the UK dropped out, European launch has basically been a French party. Even if they do go kerolox, I'm not sure where they'd start for an engine--they'd almost need to buy from Russia or the US (and if it were me, I'd go Russian). On the other hand, at the point where you're already resigned to buying foreign engines, perhaps they give into the allure of American hydrolox? You could use the STME originally intended for the cancelled American ALS, Rocketdyne Just in the meantime, of course, while they develope a sufficiently capable engine of their own.
I hate to point this out, but you have the program start date confused with the first flight. Ariane 5 began development in '88, and first flew in '96. If you want it to start in 1980, you'll need to mess around a lot with ESA--they were still doing all they could to wring performance out of the basic Ariane.
In that case, you'd almost need to design the core for solids and CCB up front, not in the future. Intended loads, mounting points, all that. If you're going to do it, why wait? Spend the money up front and do it right the first time.
As I said, the upper stage will almost assuredly be hydrolox from the start--the French have historically liked hydrolox, and they already had good engines for it, whereas they didn't have good kerolox technologies. They'd need to give the HM7B restart, but that's a lot cheaper than developing an entire new engine using entirely different fuels.

As I mentioned above, you've got the development timeline wrong. If it starts when OTL Ariane 5 did, then it's not going to be ready for flight testing until the early-to-mid 90s. You'd still be able to maybe do a flight or two to Mir, but it'll be in the decrepit years. Additionally, European launch capability on this order may have already had some butterflies on the Russian and American programs--though how much depends on whether you're going to stick to your 1980 date or the OTL Ariane 5 start of 1988.

It's a new French launch vehicle. Ariane 5 is almost inevitable. Sometimes we engineers can be incredibly dull.

First, thanks for the input. But you might want to go back to the start and re-read the whole thing. Most of the information you've provided is way off the mark ITTL.

 

[e of pi]

You might want to go back to the start and re-read the whole thing. Most of the information you've provided is way off the mark ITTL.

Arg! I'd forgotten you'd saved Europa and thus butterflied Ariane and kept the UK in ELDO and on into ESRO. I just shouldn't post during finals week, it's not good for my memory.

So...if they've kept Europa, then the RZ2 or whatever upgraded variant it's become could be clustered for your new first stage, or you could go with a new Rolls-Royce kerolox engine. To avoid pacing and get the benefits of flight heritage, I'd go with the former. I'd keep a single-engine cluster on the table for the future, but if you have a good enough engine already, why develope a new one?

The French will want to go with a hydrolox upper from the start, and there's not much reason to do anything else sine they'll probably have been already working on something a lot like the HM7B for Europa 2 and 3. Since it's going to be using existing engines, the stage hardware is the pacing item.

With that, I'd say that if you do start work in 80ish, you should be able to have something ready by the 86-88 period. My point about designing in SRB or CCB attachments from the start holds, though.

 

[Bahamut-255]

Arg! I'd forgotten you'd saved Europa and thus butterflied Ariane and kept the UK in ELDO and on into ESRO. I just shouldn't post during finals week, it's not good for my memory.

So...if they've kept Europa, then the RZ2 or whatever upgraded variant it's become could be clustered for your new first stage, or you could go with a new Rolls-Royce kerolox engine. To avoid pacing and get the benefits of flight heritage, I'd go with the former. I'd keep a single-engine cluster on the table for the future, but if you have a good enough engine already, why develop a new one?

I have given some thought to the idea of clustering the smaller RZ2 engine - or upgraded variant - which would provide somewhat greater thrust at liftoff than the 4 engine setup I was looking at. But I'd need nine such engines for the 1st stage at the 85,000Kg thrust they produce. Uprating the thrust to 95,000Kg lets me get away with eight engines and only have very slightly less thrust than the nine engines at 85,000Kg thrust. What gives me issues with it is that fitting three such stages together could be tricky. But the CCB setup could be delayed for when the 190,000Kg thrust engines are ready to mitigate the issue, at least on paper.

The French will want to go with a hydrolox upper from the start, and there's not much reason to do anything else since they'll probably have been already working on something a lot like the HM7B for Europa 2 and 3. Since it's going to be using existing engines, the stage hardware is the pacing item.

LOX/LH2 works on high-altitude/vacumn stages on account of it's high energy nature, but the density is the lowest you can find. My initial plan is to use it as an optional 3rd stage for higher orbit/earth escape payloads, much like what you see in the 3/4 stage Proton K/M. This may be a requirement since the HM7 engine has only 7,900Kg thrust(vac) though a decent 441s Isp (vac). Developing a higher thrust & efficiency engine is something I intend to look into for later on though.

With that, I'd say that if you do start work in 80ish, you should be able to have something ready by the 86-88 period. My point about designing in SRB or CCB attachments from the start holds, though.

I've already taken the boosters and CCBs into account and set the dry mass of the 1st stage accordingly when I ran the numbers. So while it appears fairly high for the Base Version, it is necessary to handle the increased loads and attachment points for the more powerful versions.

 

[Dathi THorfinnsson]

Launchers


I did some back of the envelope calculations a while back, going vaguely in the direction you're going. IIRC the RR kerosene engines were roughly as powerful as the OTL hypergolic Viking engines were. So I assumed 5 at the base of each core for a *Ariane followup to Europa 2.

Going to Kerosene means that many of the OTL problems with Ariane and its highly toxic fuel are obviated - for instance, they had to shut down the coastal highway cutting access between the eastern and western parts of French Guyana from the time fueling started until the time the launch happened.

So, I'd go
Europa 1
Europa 2
X1 (Europa 3/Ariane 1) with 4/5 engines on a single core
X2 (with probably solid boosters like OTL's Ariane 2/3)
X3 with common core boosters, too, like some of the initial ideas for Ariane 5 iOTL, which basically lost out due to the toxicity issues.

This X3 (Ariadne? Solaris? whatever X=) would, in its heaviest form, be able to launch quite a significant mass to orbit. Like Hermes, let alone a Soyuz-oid.

X4 might try fly back boosters.

 

[Dathi THorfinnsson]

Oh. And aiming for 51 degree orbit only makes sense if the benefits (such as they are) from Russian participation outweigh the huge performance hit from going into that highly an orbit.

If the Europeans have manned flight before the US gets a space station up, it would make a lot more sense to have a far lower inclination for said station. The Europeans could even do a simple Space Station (like the early Salyuts, or Tiangong (sp?)) and have the US visit THEM.

Resupplying an equatorial station is a lot easier, because you can launch every orbit, not occasional rare ones.

 

[Bahamut-255]

Oh. And aiming for 51 degree orbit only makes sense if the benefits (such as they are) from Russian participation outweigh the huge performance hit from going into that highly an orbit.

If the Europeans have manned flight before the US gets a space station up, it would make a lot more sense to have a far lower inclination for said station. The Europeans could even do a simple Space Station (like the early Salyuts, or Tiangong (sp?)) and have the US visit THEM.

Resupplying an equatorial station is a lot easier, because you can launch every orbit, not occasional rare ones.

I'm well aware of the performance penalty that's going to be paid from sending payloads into that particular orbital inclination, but given when ESA Manned Spaceflight is expected to be ready ITTL, it makes sense since Mir will be in orbit during the time it was working reasonably well - it faults and failings didn't occur until the mid 90s IOTL. So flights to Mir will be an option for them. It also allows for the possibilty of testing MTFFs - for extremely specialised experiments where conditions must be within the narrowest of tolerances - with Mir later on, though I only really plan this for the ISS of TTL.

ESA is intended to be a robust and active partner within the International Spaceflight Community ITTL, and I need to plan my moves here accordingly.

 

[Shevek23]

Being rather naively ignorant of the merits of the various particular engines, I'm out of my depth there.

Given though that the intent is to reach orbits with an inclination of 55 degrees, shouldn't they be looking for launch sites that are already at that high a latitude? And if they need to launch from somewhere to the south of that, wouldn't someplace higher up than Kourou be indicated if at all possible?

Looking at a map, it's a daunting challenge to be sure. One wants a track eastward, where a rocket that fails for any reason can fall harmlessly; Europe being on the west end of Eurasia this is very tricky! I guess the highlands of Scotland are too close to Scandinavia and the Baltic countries (including northern Germany) to be considered as a launch site? Launching from the Pyrenees is dangerously close to Sardinia and Italy itself, or rather launching from such a latitude will involve a northeast track right over France itself! Launching from Tunisia would take the rockets over Italy and Greece and Yugoslavia...same for launching from Sicily. Launching from Iceland is of course too far north!

Anyway I'd think aside from rendezvous with Russian space stations, which would be in high-inclination orbits, and quite a few utility functions over Europe that also indicate high inclination, they'd also want to launch quite a few equatorial shots. For those obviously Kourou is best. But can something be done to find a suitable launch site farther north, and ideally closer to Europe, than that equatorial site?

Another possibility is to go far far away indeed, much farther than French Guiana, to suitable launch sites at the ideal latitudes in the southern hemisphere.

When Britain was involved, and in their own approaches to a space program, Australia was where the launches were. Sadly even the South Island of New Zealand is farther north than I think you'd like.

The Falklands are much closer to Europe, and just about the right latitude. They aren't very high, and I suppose the launching weather is atrocious much of the time, and the islands are so small one doubts that any extensive infrastructure could fit there, however lavishly funded.

The only other alternative I see though would be to launch from South America, and unfortunately the Andes are on the wrong side of the continent, and the ridge would be Chilean territory while they'd want to launch over Argentina, so that's tricky political negotiations with two non-European nations.

If it is not necessary or perhaps even undesirable to launch from a latitude as high as you want your orbit to reach, perhaps New Zealand's southern tip is actually very good. Unfortunately it is literally on the other side of the world from Europe!
-----
Looking at map projections, it does seem to me that if the energetics of a launch from Kourou are not more unfavorable than one from a higher latitude, that a northeastern launch to that inclination would have about as safe a path as one could wish for. I did catch another alternate site, the Labrador coast at 55 degrees north. As with the Falklands, I guess the weather would be miserable, the site nearly as isolated, and in addition the launch path would go across one of the world's busiest transcontinental traffic corridors, for shipping and air traffic.

Also of course while on Canadian, hence Commonwealth and not at all US soil, it's still on the North American continent, which for reasons of prestige the Europeans would probably want to avoid!

I guess, if launching from the equator to such a high-inclination orbit is not significantly more costly than reaching it from a high latitude, there is a lot to recommend Kourou; for one thing it's got to be more economical to concentrate on one launch site for all than to have multiple ones. Since I don't see a good place to put a high-latitude launch site in Western Europe itself (so much shorter distance to site and the political bonus of operating directly on home soil, the way the Americans do and Soviets did (before splitting of Kazakhstan!)) the alternatives I can find that are really good (the best being southern New Zealand) are godawful far away.

Also a northeast launch out of Kourou goes right over northwest Europe, by way of the Azores, so for practical purposes there are great sites for downrange tracking and possible recovery sites for aborted manned missions, plus the prestige of the launches passing directly (a totally safe distance downrange from launch zero though!) over their home countries.

I need to understand more than I do about why high-inclination orbits are so damn costly compared to lower; from fooling around with the Silverbird launch calculator I gather that trying to launch to a lower inclination than one's launch latitude can be quite as difficult as launching to a higher one, and I do have the impression that the cheapest launch from any site is to an inclination equal to the latitude of the site, which makes sense to me. It seems odd though that the rotation of the Earth, only about 1/20 the velocity of an orbit at the most, can make such a huge difference!

But Europe's problems are geographical; the continent is just too crowded for there to be any good launch tracks near it.

If the latitude factor matters a lot, I'd think they'd want to take a good look at a site in Labrador again, never mind the trade route. It may be in North America but it's quite closely tied to Europe even so after all!

 

[Bahamut-255]

Being rather naively ignorant of the merits of the various particular engines, I'm out of my depth there.

Given though that the intent is to reach orbits with an inclination of 55 degrees, shouldn't they be looking for launch sites that are already at that high a latitude? And if they need to launch from somewhere to the south of that, wouldn't someplace higher up than Kourou be indicated if at all possible?

Looking at a map, it's a daunting challenge to be sure. One wants a track eastward, where a rocket that fails for any reason can fall harmlessly; Europe being on the west end of Eurasia this is very tricky! I guess the highlands of Scotland are too close to Scandinavia and the Baltic countries (including northern Germany) to be considered as a launch site? Launching from the Pyrenees is dangerously close to Sardinia and Italy itself, or rather launching from such a latitude will involve a northeast track right over France itself! Launching from Tunisia would take the rockets over Italy and Greece and Yugoslavia...same for launching from Sicily. Launching from Iceland is of course too far north!

Anyway I'd think aside from rendezvous with Russian space stations, which would be in high-inclination orbits, and quite a few utility functions over Europe that also indicate high inclination, they'd also want to launch quite a few equatorial shots. For those obviously Kourou is best. But can something be done to find a suitable launch site farther north, and ideally closer to Europe, than that equatorial site?

Another possibility is to go far far away indeed, much farther than French Guiana, to suitable launch sites at the ideal latitudes in the southern hemisphere.

When Britain was involved, and in their own approaches to a space program, Australia was where the launches were. Sadly even the South Island of New Zealand is farther north than I think you'd like.

The Falklands are much closer to Europe, and just about the right latitude. They aren't very high, and I suppose the launching weather is atrocious much of the time, and the islands are so small one doubts that any extensive infrastructure could fit there, however lavishly funded.

The only other alternative I see though would be to launch from South America, and unfortunately the Andes are on the wrong side of the continent, and the ridge would be Chilean territory while they'd want to launch over Argentina, so that's tricky political negotiations with two non-European nations.

If it is not necessary or perhaps even undesirable to launch from a latitude as high as you want your orbit to reach, perhaps New Zealand's southern tip is actually very good. Unfortunately it is literally on the other side of the world from Europe!
-----
Looking at map projections, it does seem to me that if the energetics of a launch from Kourou are not more unfavorable than one from a higher latitude, that a northeastern launch to that inclination would have about as safe a path as one could wish for. I did catch another alternate site, the Labrador coast at 55 degrees north. As with the Falklands, I guess the weather would be miserable, the site nearly as isolated, and in addition the launch path would go across one of the world's busiest transcontinental traffic corridors, for shipping and air traffic.

Also of course while on Canadian, hence Commonwealth and not at all US soil, it's still on the North American continent, which for reasons of prestige the Europeans would probably want to avoid!

I guess, if launching from the equator to such a high-inclination orbit is not significantly more costly than reaching it from a high latitude, there is a lot to recommend Kourou; for one thing it's got to be more economical to concentrate on one launch site for all than to have multiple ones. Since I don't see a good place to put a high-latitude launch site in Western Europe itself (so much shorter distance to site and the political bonus of operating directly on home soil, the way the Americans do and Soviets did (before splitting of Kazakhstan!)) the alternatives I can find that are really good (the best being southern New Zealand) are godawful far away.

I did a check of the numbers. Even for an ISS orbit, the payload you can send from Kourou is slightly greater than for payloads from Baikonur Cosmodrone. And it makes perfect sense to focus your launch sites to one location, economics being the primary contributary factor.

Furthermore, for GSO launches, you want it to be as near to the equator as possible, since that will minimise the propellant requirement for Orbital Inclination Changes. One reason why Baikonur GSO launches are so much more complex and inefficient relative to a Kourou GSO launch.

Also a northeast launch out of Kourou goes right over northwest Europe, by way of the Azores, so for practical purposes there are great sites for downrange tracking and possible recovery sites for aborted manned missions, plus the prestige of the launches passing directly (a totally safe distance downrange from launch zero though!) over their home countries.

I need to understand more than I do about why high-inclination orbits are so damn costly compared to lower; from fooling around with the Silverbird launch calculator I gather that trying to launch to a lower inclination than one's launch latitude can be quite as difficult as launching to a higher one, and I do have the impression that the cheapest launch from any site is to an inclination equal to the latitude of the site, which makes sense to me. It seems odd though that the rotation of the Earth, only about 1/20 the velocity of an orbit at the most, can make such a huge difference

Even at 5% the orbital velocity required, that still represents a major boost. Since that directly equates to less propellant required or more payload for the same launch vehicle. Even for 51.6 degrees, there is still a small boost offered by the Earth's rotation - unless you're aiming for a retrograde orbit for some insane reason. It only when the inclination exceeds 63 degrees or so that the benefit really dimishes.

One last point. Kourou is a good site because the stage impact zones tend to be in the Atlantic or Indian Oceans depending on where you're sending the payload using OTL Ariane 5. In fact, with my TTL Europa Successor, you can expect a greater range of orbital inclinations because the 1st stage should only impact in the Atlantic Ocean IMHO.

 

[Workable Goblin]

I need to understand more than I do about why high-inclination orbits are so damn costly compared to lower; from fooling around with the Silverbird launch calculator I gather that trying to launch to a lower inclination than one's launch latitude can be quite as difficult as launching to a higher one, and I do have the impression that the cheapest launch from any site is to an inclination equal to the latitude of the site, which makes sense to me. It seems odd though that the rotation of the Earth, only about 1/20 the velocity of an orbit at the most, can make such a huge difference!

Remember the exponentials in the rocket equation. Especially given the relatively poor ISP of chemical rockets, a smallish change in required delta-V can have much bigger effects in required fuel (and so possible payload mass).

 

[Bahamut-255]

Remember the exponentials in the rocket equation. Especially given the relatively poor ISP of chemical rockets, a smallish change in required delta-V can have much bigger effects in required fuel (and so possible payload mass).

A fact which even I know with my - admittingly - limited knowledge of the complex aspects of rocketry and orbital mechanics.

What I do know, however, is that NTR is off the cards for more than just Public Relations reasons. So don't expect to be seeing it in any serious detail here. More will follow once all of the current topic is properly resolved.

 

[Workable Goblin]

A fact which even I know with my - admittingly - limited knowledge of the complex aspects of rocketry and orbital mechanics.

What I do know, however, is that NTR is off the cards for more than just Public Relations reasons. So don't expect to be seeing it in any serious detail here. More will follow once all of the current topic is properly resolved.

NTR has issues with low thrust-to-weight ratios and an only modestly higher ISP. That's before you start on all the problems associated with the "N," of course. You'd have to ask e of pi to get more, but IIRC the supposed benefits of NTR can be totally eliminated by the T/W issues under rather modest assumptions.

NEP is something completely different because electric drives have closer to 10x than 2x the ISP of chemical rockets, but obviously you can only use them in space. You still have to deal with the "N" problems, though.

 

[Bahamut-255]

NTR has issues with low thrust-to-weight ratios and an only modestly higher ISP. That's before you start on all the problems associated with the "N," of course. You'd have to ask e of pi to get more, but IIRC the supposed benefits of NTR can be totally eliminated by the T/W issues under rather modest assumptions.

NEP is something completely different because electric drives have closer to 10x than 2x the ISP of chemical rockets, but obviously you can only use them in space. You still have to deal with the "N" problems, though.

I know. That's why OTL, SEP has been the most developed of the advanced propulsion systems to date, which gets the same 5,000s Isp as NEP, only without the Nuclear Baggage. And one which could see more use, we'll just have to wait and see about that.

As for NTR, I think the best T/W ratio accomplished was 5:1 or so IIRC, well short of the 30-130:1 of a chemical propulsion system. If I did the basic numbers right, you'd need an LEO total payload of about 200,000 before a benefit came - as if that's gonna happen anytime soon! Both ITTL and IOTL!

 

[Shevek23]

I did a check of the numbers. Even for an ISS orbit, the payload you can send from Kourou is slightly greater than for payloads from Baikonur Cosmodrone.

Every possible orbit crosses the equator so I suppose the only downside to launching from there would be if the momentum from the Earth's rotation exceeds the maximum west-to-east momentum the desired orbit has; then you have to expend delta-v actually braking away the free gift of momentum. I guess the 63 degree inclination you mention below this quote is the inclination where that becomes true; for any lower-inclination orbit, the rotational momentum is part of the velocity you need, so one comes out ahead.

Then improving on Kourou would involve either seeking a lower latitude still--but it goes as the cosine of the latitude, and cosine of 5 degrees is practically equal to the cosine of zero, which is 1. So that wouldn't make much difference. Or seeking a higher altitude, which would boost the rotational momentum--just a bit, but more than closing that 5 degree gap would accomplish, and elevates the launch site higher in the atmosphere, reducing air drag somewhat.

So the ideal launch site would be a very high mountain plateau (but not so high your technicians have trouble breathing!) right on the east coast of some very broad ocean, hopefully one with good weather and lots of suitable islands for tracking/abort recovery bases, right on the equator. I don't think there is any site in the world that meets that description exactly. I know Arthur Clarke back in the 1950s (or someone anyway, I might be mixing up some Clarke stuff I read in third grade with some reprinted old Reader's Digest stuff in my school library) touted New Guinea as coming close. But that's as much on the other side of the world from Europe as New Zealand! And there are serious access issues to the highlands; building and supporting the infrastructure there--well, it would be a boon to the Papuan government I guess, but quite a bill for anyone to foot. If anyone in any alternate timeline develops a New Guinea highland launch site, I guess it ought to be someone who lives reasonably close by, like an Australian/Japanese coalition or someone like that. And there are a lot of islands in the eastward downrange for launches to dodge.

ITTL I guess as long as Britain stays in the ESA coalition, Australia is likely to be involved in it too. But unless one can show the benefits of a higher launch site trump the relative accessibility of Kourou to European projects, I guess that is the basket the ESA will put all its eggs into. Which makes Australia very peripheral to the projects; I can see them eventually hiving off ESA and going into partnership with various East Asian nations to develop their own regional capability--and they might want New Guinea, but they too might also choose from a wide variety of much more easily accessible sites, such as the Australian sites the British started with. Or some Pacific or even Indian Ocean island with a big empty to the east of it.

Of course even given the trajectory of the "Asian Tigers" matching those of OTL it might be some time before even a consortium of them and the Australians has the loose change necessary to put up a really major space center anywhere. Even bringing Japan into it, and avoiding or at least mitigating Japan's economic miseries compared to OTL, would probably put them a decade behind Europe. If one could diverge both China and India so that they too could be partners in this grand coalition instead of each seeking its own independent space capability, I think that might make the eventual scale of the enterprise very impressive, but I doubt it would accelerate the timing a whole lot; in some other Alt-Timeline really grand things might be happening about now, but as late as 2000 they'd just be getting going.

The only other decent contender for the "ideal" launch site I described above would be the highlands just inland from the east coast of equatorial Africa, that is somewhere near Kilimanjaro Mountain. But the earliest part of the ground track would go right over densely inhabited land of course, and while it's somewhat more accessible than the highlands of New Guinea I don't think it's as high. Any regional powers of the western Indian Ocean area that might want to band together to support such a site (say, Saudi Arabia for instance) might almost as well just join a coalition for building one in New Guinea or some more accessible if lower site fringing on Indonesia. So I doubt that's an extremely likely alternative.

And it makes perfect sense to focus your launch sites to one location, economics being the primary contributary factor.

No argument here! When I took a look at a 50+ degree inclination launch northeast from Kourou and how it had that grand sweep of empty and yet well-monitored ocean, only to pass directly over Europe itself, I realized it was perfectly good, except for the low-altitude issues, which of course it shares with Canaveral. I didn't look so hard at the angles of tropical (ie, ecliptical, for Lunar and Solar System launches) or equatorial (for geosynch) but even for the latter there is a good stretch of ocean before crossing Africa. I did look at a southeast alternative path to your 51.6 degrees (it doesn't matter, at any latitude lower than one's desired inclination, whether you aim northeast or southeast, as far as achieving the desired orbit goes, I think) but that of course takes it right over the eastern tip of Brazil. But a fan going from due east (for a 5 degree inclination, to achieve dead-on 0 inclination would take some extra push) up to 60 degrees or so passes over a goodly stretch of ocean and so in that very broad range Kourou is obviously a good site. ESA clearly doesn't need anything more, except maybe a dedicated polar orbit site (launching due north from Scotland, Norway, or even Iceland) for those extreme orbits. And I daresay even a low satellite has a good view of the poles even from a 60 degree orbit! So the economics of concentrating on one launch site will probably prevail.

After all, OTL NASA has yet to develop other sites than Canaveral, though it is so much higher latitude and has no altitude at all, and withal suffers both from tropical storms and (as Challenger starkly demonstrated) continental cold snaps too. One might think they'd think of doing something in Hawaii, or Puerto Rico, (neither being equatorial, but both being significantly south of Florida, both having both some serious highlands--the Big Island of Hawaii being downright mountainous, and also wide oceans downrange) not to mention the tiny Pacific islands south of Hawaii. But the only seriously developed alternative, done by the Air Force for its own needs, was Vandenberg, chosen for polar launches apparently not so much because it is so much farther north than Canaveral (it isn't, very) but because of the clear expanse of ocean south of it. I see some site in Alaska, I guess, in the Silverbird calculator's list of launch sites, but I can't believe it is developed all that much.

So that's a powerful testament to the sheer inertia of having heavily developed one site, even it isn't just ideal.

So, no argument. Kourou is pretty good.

Furthermore, for GSO launches, you want it to be as near to the equator as possible, since that will minimise the propellant requirement for Orbital Inclination Changes. One reason why Baikonur GSO launches are so much more complex and inefficient relative to a Kourou GSO launch.

Well, sure, I believe I said that--geosynch obviously is best done from dead on the equator if you can get there.

And yet we don't have an abundance of such equatorial sites globally; as I suggested one might think that by now there might be one on the fringes of Indonesia somewhere, at least. But no. Kourou is apparently quite good enough, even for people who live on the other side of the world from it.

 

[Shevek23]

Failing geometry forever! More love for Kourou

I remarked above that a higher launch site (such as the New Guinea highlands) would be better than a sea level one. That's true, generally speaking, but I hadn't thought through the geometry in remarking that a higher site can offset the losses due to moving away from the equator, hence inward toward the Earth's axis. While it is true that the variation is relatively slight for low latitudes, the fact is that 5 degrees away from the equator (Kourou for instance is a bit over 5 degrees north) you'd need a mountain 40 kilometers high to have the same angular momentum as at the equator! In that range it goes as the square of the distance, so just one degree away going up a kilometer or two can indeed negate the loss.

It's still good to get higher, since the air will be thinner there. But another thing to consider is that average wind velocities tend to be higher at greater altitudes, so the adverse effect winds have on launch conditions need to be considered too.

So a sea level site that is right on the equator is better than I was giving it credit for, another point for Kourou.

Another thing to consider is the prevailing weather conditions; for that armchair musings on spherical geometry are no help and one must simply consult weather history. I don't know how the cumulative number of days of high winds and lightning storms at Kourou compares to say Cape Canaveral, but while as a tropical location I bet it is fairly stormy there, I would expect it to be somewhat calmer than Canaveral, precisely because it is the equator, in the middle of the tropical zone, and not on a boundary between that and the temperate zone like Canaveral! At least I'd bet it never freezes there!

Still, given that a spot right on the equator is better than one 5 degrees off of it (slightly, just a fraction of a percent) I wonder how much thought has been given to making really big floating launch barge complexes.

For European projects it's hard to beat Kourou; scouting for the best location in the Atlantic Ocean you'd be at the shore of South America at the equator, since you'd be trying to get as far west as possible to get clearance from Africa. I suppose the French sited at Kourou rather than that point for political and related infrastructural reasons; they launch from an overseas department of France, rather than having to negotiate with the government of Brazil, and as an overseas French department, French Guiana presumably had convenient infrastructure to build on, and upgrading it is, in administrative and bureaucratic terms, spending money "in France" and not overseas! Legally speaking. Also for northeast, high inclination launches if not launches due east (the bulge of Africa westward compensates for Kourou's westward location) the range of launch tracks clear of any land seems broader than the exact equatorial site.

And I think the equator crosses the South American coast pretty much in the middle of the Amazon River delta, so Kourou, while no mountain plateau, is somewhat higher and less soggy ground.

 

[Bahamut-255]

ESA Post-Europa Launch Vehicle - Part II

I think I got the numbers good for the Base Version, so now attention can be turned towards the augmented variants. For this, a combination of smaller to medium sized boosters is being considered, alongside the CCB setup, which I expect to deliver the greatest payload performance to this family of launch vehicles.

Having selected a proper SRB and LRB size for the Launch Vehicle, the payloads (Kg, 225x225Km, 52 degrees) I am receiving for it are as follows:


Base: 12,940

2 SRB: 15,050

4 SRB: 18,020

2 LRB: 18,135

4 LRB: 23,950


These are the numbers I've crunched so far. As for the CCB setup I favour. That one is a little trickier. If using the Boeing Delta IV Heavy and Lockheed Martin Atlas V Heavy - where propellant-preserving throttle down is used - I can expect a payload of about 30,000Kg to the orbit described. But the propellant cross-feed setup for the Falcon 9 Heavy allows me a payload of 62,350Kg. While the higher number certainly sounds better, I don't really have a mission requiring such a payload. Furthermore, I have doubts that Propellant Cross-Feed would make it past the design phase. So I don't really plan on using it, especially in the early phases.

The LRBs planned for it are expected to use the same 190,000Kgf engines that are planned for the 1st Stage, so would not see use until after they have been developed and tested. So the SRBs are expected to be the initial means of payload augmentation, likely remaining in use for the duration of the LV lifespan.

And I still need a good name. Seeing that this design is far removed from the initial Europa LV. Does anyone have any good suggestions?

 

[Shevek23]

I believe throttling down the thrust does not directly conserve propellant; rather the opposite. If your rocket is capable of a given maximum thrust and you then throttle it down, clearly you are taking longer to achieve a given delta-v; this gives gravity a longer time to drain off some of your achieved velocity.

However, if one bears in mind that many payloads--human beings for instance, and delicate scientific equipment for another--can only take a certain limited amount of acceleration stress, one has to design an orbital rocket to thrust only to the thrust that gives that maximum G-load when the mass is minimal, ie at burnout. A fixed thrust rocket designed not to overstress the payload must therefore be delivering less acceleration than the load can take at all times prior to burnout, meaning that a fixed-thrust rocket that doesn't exceed that limit must require more time also, and thus suffer greater than necessary gravity losses.

Staging of course is a rough form of throttling; designing the successive rocket groups of the various stages with that maximum G-stress at burnout of each stage in mind approximates the thrust of an ideal throttled rocket, in steps, and also gets rid of mass a realistic ideal single-staged throttled rocket would be stuck with--tankage mostly. The lower stages will generally have less of a ratio between the maximum and minimum rocket masses during their operation, and so will operate closer to the ideal curve.

But, if the rocket engines can be throttled over the necessary range without undue costs--in engine cost, in loss of efficiency--then they can be designed to exert the full maximum acceleration the payload can take, and throttle down to maintain that throughout the launch. If one can afford to make the separate engines of successive stages all throttle, we get the advantages of staging as well (offset by needing two or three sets of engines, but their weight tends to be relatively low, and if they are standardized and launches are frequent the costs of producing even non-recoverable engines will come down). If we can't, it's probably better to save the throttling for the upper stage engines.

Note that constant-thrust rocket that can match the full thrust of the throttleable one will give lower gravity losses due to higher acceleration and hence less time under thrust, but that's because the rocket is subject to higher G-stress. Scaling it so its maximum rather than minimum acceleration is within tolerable limits means it will take longer, rather than less time, to achieve a given velocity target, hence higher gravity losses.

So in that sense, throttled engines can save propellent, by being superior to an acceptably powerful constant-thrust engine, which will be underpowered in all moments of its operation save the last one.

Of course this means the throttleable engine has more thrust available to it than one needs in all moments of the launch but the first one, and hence is heavier and more costly--also inherently more costly than a constant thrust engine due to its greater complexity, and presumably somewhat heavier per unit of thrust produced too.

But the excess capacity of the throttleable design might make it more versatile in that upgraded clusters, boosting higher loads, might make more use of its maximum capability. It means that to a limited extent, one can "stretch" a given rocket design for some combination of higher payloads and higher orbits, simply by adding on more fuel (with associated tankage of course) if one is prepared to accept a lower acceleration and associated gravity losses in the early part of the launch. Or one could instead strap on supplemental boosters, say solid fuel units or cheaper, simpler constant-thrust liquid fuel ones, to make up the deficit, throttling down the main engine to keep the G load at the design maximum as the rocket burns up propellant and ejects it, until it is time for them to drop off, whereupon the main engine (if its throttling is this good) can be brought back up to full thrust until the remaining mass falls below the original design launch mass.

So designing in as much throttle capability as one can achieve at not too high a cost seems like a very good idea to me! Just bear in mind, its costs might not be too high compared to the basic cost of the minimum possible rocket engine, and might seem to shrink in the light of the benefits, which make for a more efficient launch. But they won't be zero.

Making the engines fancy makes me want to try to figure out some scheme for recovering and reusing them. Of course an engine that is only designed for one use can presumably be made somewhat cheaper and a bit lighter, whereas recovery is difficult and even a very good reusable engine will have only a limited number of uses before one had better scrap it!

 

[Shevek23]

See bottom line for my favorite nomination

...
And I still need a good name. Seeing that this design is far removed from the initial Europa LV. Does anyone have any good suggestions?

{Pre-submission edit--I think with my mouth running, my stream of consciousness meanders as it will--my favorite suggestion is at the bottom of this post.}
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Thinking mythically, I want to suggest the names of the bridges to the domain of the gods in various European mythologies. I believe both the Greeks of the Homeric/Hesiod age and the Nordic Eddas identified this bridge with the rainbow, so the Greek mythic name would be "Iris." But that sounds to modern ears too much like something associated with optics, I suppose.

The bridge itself was named Bifrost in Nordic myth; I'm not actually sure that was a term for rainbows too. Heimdal was the Aesirc god who had charge of that bridge.

In Greek mythology the latter role (and associated function of the "psychopomp," escort of the spirits of the deceased to their afterlife destinations) fell to Hermes. Which I suppose had something to do with the OTL project of a manned reusable orbiter spaceplane being given that name. (Also of course Hermes is wingfooted and swift, and while a mere orbiter is a slow truck of a craft compared to deep-space craft, it's certainly faster than anything that operates on Earth!) One might want to look into the darker associations of these god names though--Hermes/Mercury also being the god of thieves for instance! Heimdal comes across as a very straight arrow of a god IIRC, but with the Eddas there is that whole Ragnarok association to watch out for of course!

Perhaps someone up on Celtic myth can suggest something more imaginative than Hermes or Heimdal? Going to Slavic myth might, in the 1980s and '90s, seem to send the wrong sort of political message! I am not even trying to mine Christian medieval mythic systems because naming a rocket system after some saint might simultaneously seem oppressive to those seeking distance from Europe's historical established churches and at the same time sacrilegious to some kinds of serious believers in same.

I do suspect Arthurian myth might be up for grabs, but any famous Knights of the Round Table names I can think of have their associational drawbacks, given the nature of the Matter of Britain!

Trying to find a name out of Tolkien's canon would probably seem insanely geeky (and obscure), and would have the added effect of making the late professor spin in his grave. (Harnessing his revolving corpse for power seems the obvious next step, having the added virtue that such a project would cause his spin to accelerate without bounds, offering the prospect of unlimited energy! Unless the spin reaches the point where he simply fragments into a ball of plasma and blows a big hole in whatever graveyard he's in...)

If the name Pegasus is not already taken in your timeline, it seems like a very logical one for a system meant to routinely launch all manner of loads into orbit and perhaps beyond. The only Nordic counterpart I can think of is Odin's eight-legged Slepnir, and that was no drafthorse! (Neither was Pegasus, but the Greek flying horse is harnessed for the purposes of a mortal hero, while the Nordic one is the steed of a god, a supreme god in fact, so...)

Trying to think of famous ships or horses or the like, or names of historical figures, seems fraught with the different perspectives of the varied nationalities making up ESA. Poetry ("Locksley Hall") anoints the word "argosy" (with a capital A, "Argosy!") with grandeur that might offset the implication of very pedestrian commercial applications--which after all, will hopefully pay the bills, or at least offset the costs significantly.

I considered and rejected "Hansa" for that reason--we want to strike a balance between suggesting that the system is indeed workaday and routine and reliable and a utility, and making it boring or even, to people put off by overcommercialization, money-grubbing and thus oppressive.

I find myself erring on the side of mythic grandeur obviously! Choosing names from the European Age of Exploration would tend to send the wrong message to potential Asian and African and South American partners and customers, I fear.

------
I think I have hauled in all the brainstorming fish my wacky mind can harvest tonight; if I think of something else I'll add it. Of everything I've suggested, my favorites are Argosy, Pegasus, and Hermes. The latter two have of course been used, at least on paper in the last case, OTL.

Pegasus OTL is, if I recall correctly, a very light launch system carried aloft on airplanes and drop-launched (or fired from the plane, I'm not sure which) at high subsonic speeds in the stratosphere--thus nearly doubling the push the Earth's rotation gives, achieving significant height and avoiding most of the atmosphere as well. Perhaps one should reserve this name for a system that works along similar lines on a grander scale?

So I'm liking Argosy. I think it strikes a good balance between the promise of a good workhorse of a system people can come to take for granted, also suggesting frequent and reliable operations and significant payloads, with a touch of grandeur and etherial associations. The name is derived from the Classical Greek mythic ship Argos of course; the voyage of Jason and the, um, acquisition of the Golden Fleece (from "Colchis, at the world's edge") has I think some mythic record of the entrepreneurial aspect of ancient Greek society--in their pre-classical years, they, like the Vikings some thousands of years later, quite naturally tended to blend raiding and trading rather ambiguously. Also Jason and the Argonauts were more or less under the rubric of "explorers," voyaging to the World's End and all that.

But the Argos gets a baptism in medieval Christendom as it were, and acquires a patina of a very similar medieval blend of magic and merchantilism, and becomes a word for ships--especially and particularly wide-ranging and large-holded cargo ships. And gets a polish of Romantic and Victorian era poesy.

I think the word comes out quite serviceable for our purpose!

So, to bottom line it, "Argosy" is my submission; for runners-up see above.

 

[Shevek23]

By the way I haven't noticed in the only launch calculator I know of, the Silverbird Astronautics Launch Vehicle Performance Calculator, any sort of option to specify throttling the thrust. I presume it simply assumes constant thrust for any stages you specify, with the result that specifying a brisk and businesslike 3 G launch thrust would wind up squashing any astronauts you send up into jam at 27 Gs or so at burnout! Thus I suppose the payloads it gives tend to be overestimates, unless the option of variable thrust is implicit in the very wide range of actual payload masses it suffixes "the" mass with. Others who know that calculator better may be able to shed more light on this, but unless you are using a different one that lets you specify a maximum acceptable acceleration, I fear you had better revise the payloads down (or your launch system up).

Perhaps you've already attempted to allow for that, by putting in a compromise thrust that should work out to the average thrust the actual throttled engine will put out, starting with a higher one and ending with a lower one? That would still skew the results, but they might be in the right range then I guess. Again, ask the experts, I'm just fooling around I fear.

Relating tangentially to my suggestion of "Argosy" as the overall name of the family of launchers, the Russians have used the name "Kliper," which is I believe simply Russian for "Clipper," as in a clipper ship, for one of their abortive steps forward beyond Soyuz. So, the general notion of picking a name from a type of ship or presumably other conveyance is out there.

I still think Argosy is more apropos, since a "Clipper" implies a variation on the basic theme of a transport workhorse that is faster and ranges farther. We would want to start with a frank admission that we are looking at starting with a stolid, reliable draft horse, and leave the thoroughbreds for a future generation.

But a grand, noble, romantic drafthorse that sets hearts a-flutter!

Argosy!