I've been a die hard fan of the Gateway concept in its varied shapes since its inception in 1999. What bothers me with LOP-G - no clear role - SLS-Orion are too expensive, and LOP-G is only "cannon fodder" to provide SLS with payloads - Distant Retrograde Orbit: EML-1 and EML-2 are better, as underlined in another post. It is a shame, because (I will seek an earlier post of mine) there really are boatload of missions that could be done from an EML-2 Gateway, a multirole platform. From telescope servicing to GEO cleanup, and many other. Oh well, see my post on the other thread (before it was moved to the space policy section) https://forum.nasaspaceflight.com/index.php?topic=45240.msg1810063#msg1810063Then again, the ISS started completely and entirely wrong (Freedom - Alpha - Fred) yet, since 2010, it had proved its worth - see Ed Kyle post, he is perfectly right. NASA really turned lemons (Freedom) into lemonade (current ISS).
Here is my take. LEO is a better place for commercialization. Smaller rockets are easier to fund and develop and reusability is easier from LEO than from deep space. As presented there really isn’t enough for commercial to do. Too few flights needed. I am not against a station near the moon, but I fear that instead of an additional destination to go to it becomes the ISS replacement and human spaceflight gets reduced to nothing more than one flight every other year or 2 flights per year that only stay in space for a few weeks. Compared to the ISS that is a great reduction of capability. The ISS gets about 4 cargo flights a year and this thing looks like it might only need 1-2. In addition the ISS is planned to get another 2 flights per year from each provider for crew. If SLS launches the crew then there is no work for commercial to do in terms of crew.As for international partners they have their own objectives in space and ESA, Japan, Canada would be willing to go almost anywhere NASA would. I don’t see any advantage here at all. In fact I dare say that this would be something that slows it down as each partner adds their own requirements.I also don’t like the reusable lander. I love reusability, but I see no such item. The problem with a lander is that most of the mass is propellant and I see no plan to cheaply send propellant to this station. I see no use of say a SEP tug and a smaller rocker to send a tanker to the station or the use of BFR(or something like it) to send and retrieve a lander from the station for servicing on Earth. The tanker craft will need to cost substantial less than the lander in order for it to make any sense and the launch costs are going to be about the same for sending the tanker as sending the lander, so how does reusability save money in this instance? The tanker is going to need many of the same systems as the lander so making it much cheaper is going to be hard.
Time has a balanced article discussing the pluses and minuses of the Lunar Gateway....http://time.com/5342743/nasa-moon-mars/
Quote from: MATTBLAK on 07/21/2018 05:21 amA 'Lunar Gateway' would only be a 'success' or useful if it included a small/medium propellant depot for a reusable, crewed Lander that was based there. And because of the Lander; it would have to have the right orbit to allow good access and coverage to much of the Lunar surface for useful periods of time - could someone nail down for me/us what type of orbit that would be?Without a Lander based there, I'd say the Gateway serves little purpose...A refueling station is needed for a reusable lander. Agreed. The station would also have to support the lander in other ways. Cargo transfer. Human transfer and temporary habitation. Maintenance and testing.
A 'Lunar Gateway' would only be a 'success' or useful if it included a small/medium propellant depot for a reusable, crewed Lander that was based there. And because of the Lander; it would have to have the right orbit to allow good access and coverage to much of the Lunar surface for useful periods of time - could someone nail down for me/us what type of orbit that would be?Without a Lander based there, I'd say the Gateway serves little purpose...
Quote from: edkyle99 on 07/21/2018 02:50 pmQuote from: MATTBLAK on 07/21/2018 05:21 amA 'Lunar Gateway' would only be a 'success' or useful if it included a small/medium propellant depot for a reusable, crewed Lander that was based there. And because of the Lander; it would have to have the right orbit to allow good access and coverage to much of the Lunar surface for useful periods of time - could someone nail down for me/us what type of orbit that would be?Without a Lander based there, I'd say the Gateway serves little purpose...A refueling station is needed for a reusable lander. Agreed. The station would also have to support the lander in other ways. Cargo transfer. Human transfer and temporary habitation. Maintenance and testing.I'm not so sure about that. Assuming lander propellant comes from earth and not from the moon, maybe the lander simply docks with a tanker, propellant is transferred and then tanker and lander go their separate ways, no station needed. Ditto for human transfer.If the point is to build a base on the surface, wouldn't you likely do maintenance there? If no surface base is foreseen and the plan is sorties globally, then maybe the case for high-orbit station increases. But, given that just operating LOP-G, never mind funding landers or surface operations, will likely cost over $3 billion a year, you have to ask whether it is a net benefit.
LOP-G looks like a big compromise to me:- It gives SLS/Orion something to do.- It's far cheaper than an outpost on the lunar surface.- The modular structure allows for contributions by international/commercial partners.- From a science POV it actually seems relatively useful. Again, given the budget limitations.
Quote from: Oli on 07/22/2018 01:33 pmLOP-G looks like a big compromise to me:- It gives SLS/Orion something to do.- It's far cheaper than an outpost on the lunar surface.- The modular structure allows for contributions by international/commercial partners.- From a science POV it actually seems relatively useful. Again, given the budget limitations.What scientific benefits do you see?We hear about tele-operated rovers on the lunar surface. I can see why a low-latency link to a controller on LOP-G would be helpful, but, when we have self-driving cars on earth coping for the most part successfully moving hazards (other vehicles and pedestrians), I struggle to imagine that it's a great advantage in the moon's very static environment.You get to soak astronauts in the interplanetary radiation field, which you can't do on ISS. But only for about six weeks at a time, so I'm not sure it's all that relevant to preparing for missions to Mars.
Orion/SLS (Block 1B) is supposed to have a 'surplus', co-manifested payload ability of about 10 metric tons. Perhaps the Orion could bring a tanker module with it each time to refuel a reusable Lander? Just an idea...
of all the "good things" the notion of low latency link to a controller seems like the most made up one
- It gives SLS/Orion something to do.
- It's far cheaper than an outpost on the lunar surface.
- The modular structure allows for contributions by international/commercial partners.
- From a science POV it actually seems relatively useful. Again, given the budget limitations.
Quote from: MATTBLAK on 07/22/2018 01:39 pmOrion/SLS (Block 1B) is supposed to have a 'surplus', co-manifested payload ability of about 10 metric tons. Perhaps the Orion could bring a tanker module with it each time to refuel a reusable Lander? Just an idea...Hmmm..... The Apollo LM's total propellant load (ascent and descent stages together) was about 11 tonnes. An Apollo-style lander today could no doubt get away with less propellant by saving weight and burning, say, lox/methane or maybe even lox/hydrogen rather than NTO/Aerozine 50. But the dry weight of the LM's ascent stage was less than a quarter that of the descent stage. If you want a reusable lander, you're going to have to haul something roughly equivalent to the descent stage all the way from the surface back to the staging point, and that means burning a lot more propellant. That propellant itself needs to be landed on the moon in the first place, so we're talking about a much larger vehicle.Then there's the fact that, delta-V-wise, LOP-G is about 700 m/s further (one way) from the lunar surface than was the Apollo LM when it began its descent from LLO.So I don't think Orion/SLS's 10-tonne co-manifested payload capability helps much for fueling a crewed lander.
A cislunar gateway station makes sense as one of the last pieces of the transportation architecture, after lunar surface spacecraft are already using lunar ISRU propellant for the return trip. Making it the first piece of infrastructure is like building container ports before clipper ships.Delivering terrestrial propellant to a cislunar station is big PITA compared to LEO. A lunar lander based at LOP-G would be cryogenic, probably hydrolox. The only conceivable providers would be ULA with ACES and Blue Origin with TBD. The ACES tanker would be expendable and would have a cost disconcertingly close to that of an EUS. Who knows what Blue could bring to the table in terms of a long-coast cryogenic tanker, but reusability seems doubtful.These tanker missions are going to be expensive, there may not be more than one capable provider, and the NewSpace players will struggle to identify how developing to these requirements could be helpful for their proprietary roadmaps.If we're going to be pushing an expendable ACES full of propellant out to cislunar orbit, then we might as well give it the landing accessories from the DTAL concept and just land it on the darn surface.
Delivering terrestrial propellant to a cislunar station is big PITA compared to LEO. A lunar lander based at LOP-G would be cryogenic, probably hydrolox. The only conceivable providers would be ULA with ACES and Blue Origin with TBD. The ACES tanker would be expendable and would have a cost disconcertingly close to that of an EUS. Who knows what Blue could bring to the table in terms of a long-coast cryogenic tanker, but reusability seems doubtful.