Nibb31

Sorry for the repost: Reusability doesn't necessarily reduce launch costs. The Shuttle is a good illustration. There are many other factors that need to be taken into account, and reducing the cost of the hardware is only a small part of the problem. There is a rule of thumb in the space industry called the rule of fifths: "One fifth of the budget for the satellite bus, a fifth for the rocket, a fifth for ground systems, a fifth for the payload, and the rest for various systems work (e.g. integration)." The biggest cost isn't propellant or even hardware. It's manpower. There are thousands of technicians and engineers involved in a space project, many of which are typically high-pay-grade professionals, but there are also administrative costs, HR, training, maintenance, facilities, energy, transport, etc... Reusing part of the hardware only saves you some of the manufacturing wages, but you still have to pay for all the infrastructure and other fixed costs. Ultimately, if reusing the first stage only impacts the fifth of the budget that is allocated to the rocket, then in that fifth, you still have the cost of refurbishing, testing, transport, refueling, etc... and the upper stage isn't reusable yet, so end customers are potentially looking at a rough estimate of much less than 20% savings on their project compared to an expendable launch vehicle. You're looking at a 10% saving on the total project, at best. Also remember that the reusable Falcon 9R will have a reduced payload. It will be competing with the medium-lift Soyuz market, not the heavy GEO comsat market. And remember, some of the fundamental systems haven't been proven yet. Nobody knows yet if a Merlin engine can actually restart facing a supersonic airflow, or if the lightweight tank structure can resist the stress of reentry and landing without damage. This is stuff that has hardly been researched, let alone tested, and yet the whole concept relies on it working. There is still a long road before anyone can assess the idea as feasible. There are other ways of making stuff cheap. For example, mass production of disposable items. That is the route that Arianespace is following with the Ariane 6: 4 near-identical SRBs per rocket for 12 launches per year means that the factory has to churn out nearly 50 solid booster cores per year. In space terms, that's mass production, and has the potential to massively reduce costs. SpaceX is also going this way, with a facility that is designed to build 400 Merlin engines per year, the equivalent of 40 falcon 9s. But that pretty much flies in the way of their reusability plans, because once SpaceX starts reusing all those Merlins, their production facility has to slow down and loses its competitive advantage. Add to the fact that the commercial launch market isn't expanding at a huge rate. The comsat market is reaching saturation while land-based networks are becoming more pervasive. The institutional market is under a lot of pressure too. And new markets will need more than a 20% discount to become viable. In fact, there isn't really much demand for a higher launch rate right now. So, you see, there's very fine balance to be found in the industry, and I applaud SpaceX for trying something new. But this is an industry where technical achievements, no matter how impressive they are from an engineering standpoint, don't always become an industrial success. The success of SpaceX relies on much more than just bringing their rocket back to the launch pad.

No, it would need to burn way more fuel to cross the Atlantic than to go back to KSC. A better bet would be a launch from Texas and a landing in Florida, but even then it would need an extra boost or else it would land in the middle of the Gulf of Mexico. On a conventional launch, the first stage only splashes down 2 or 300 km east of the launch site.

There is a payload penalty. The Falcon9R will have a payload of 7 tons to LEO instead of 13 tons for Falcon 9-1.1, which makes it useless for the GEO comsat launch market, but it should still be able to launch a Dragon to the ISS. Whether it's economical in the long run or profitable has yet to be seen.

I really wish we could have a Tapatalk plugin on this forum... *sigh*

It's enough for a decent lunar sortie, even though none of them are planned. Orion won't do ISS taxi missions, but it is supposed to do taxi missions to the DSH or EML-2 station. The 21-day duration is for powered-up mode. It is supposed to be powered down when docked to a Mars vehicle or DSH.

The ARM is a bit risky for and Orion/SLS validation mission. First of all, it depends on technology that isn't part of the Orion/SLS mission and is unproven. Secondly, the mission relies on docking and EVA which are kind of pushing boundaries for a first flight. A proper validation mission should go through a series of tests to verify that manoeuvering, life support, and other functions work properly before committing to a rather complex BEO flight involving EVA, docking procedures, and engine restarts. The vehicle would have more instrumentation than on an operational flight and there should be passive abort provisions throughout the mission. By comparison, the first EVA on the Shuttle program was on STS-6, and Apollo was on its third manned flight (Apollo 9). I find it risky to plan an EVA for the first manned flight on a brand new vehicle.

DreamChaser is missing. Orion will have a solar panel arrangement similar to ATV, not those circular panels.

If you are interested in space, you should orient your career into microgravity and partial gravity biology research. Partial gravity is something that we know practically nothing about. Cosmic radiation is another center of interest for space biology.

What's new about this? the ARM has been scheduled for the EM-2 mission, or even EM-1, for months now. The original plan was to send Orion to a free range asteroid, but it turned out that the trip would be too long for a single Orion, and because there is no money to develop a hab module, NASA's medical committee vetoed it. This is why the current plan is to send a SEP tug with a huge plastic duffle bag to capture a tiny 10-meter asteroid and to bring it within range of Orion in EML1 or 2. The long pole in the project, of course, is the famous SEP tug/duffle bag contraption... like all mission hardware for the SLS, there is no real budget and development can only start when SLS development is done, which means that SLS will spend its early years as a hangar queen waiting for mission payloads. Finally, the whole point of the mission, other than to demonstrate Orion/SLS, is dubious. The wrapper bag technology doesn't scale well for future bigger rocks, and there isn't much benefit from sending humans to scrape samples off of it instead of a rover.

Reusability doesn't necessarily reduce launch costs. There is a rule of thumb in the space industry called the rule of fifths: "One fifth of the budget for the satellite bus, a fifth for the rocket, a fifth for ground systems, a fifth for the payload, and the rest for various systems work (e.g. integration)." Reusing the rocket only impacts the 20% of the budget that is allocated to the rocket. In that fifth, you still have the cost of refurbishing, testing, transport, refueling, etc... so end customers are potentially looking at a rough estimate of less than 20% savings on their project compared to an expendable launch vehicle. Also remember that the reusable Falcon 9R will have a reduced payload. It will be competing with the medium-lift Soyuz market, not the heavy GEO comsat market. And remember, some of the fundamental systems haven't been proven yet. Nobody knows yet if a Merlin engine can actually restart facing a supersonic airflow, or if the lightweight tank structure can resist the stress of reentry and landing without damage. This is stuff that has hardly been researched, let alone tested, and yet the whole concept relies on it working. There is still a long road before anyone can assess the idea as feasible. There are other ways of making stuff cheap. For example, mass production of disposable items. That is the route that Arianespace is following with the Ariane 6: 4 near-identical SRBs per rocket for 12 launches per year means that the factory has to churn out nearly 50 solid booster cores per year. In space terms, that's mass production, and has the potential to massively reduce costs. SpaceX is also going this way, with a facility that is designed to build 400 Merlin engines per year, the equivalent of 40 falcon 9s. But that pretty much flies in the way of their reusability plans, because once SpaceX starts reusing all those Merlins, their production facility has to slow down and loses its competitive advantage. Add to the fact that the commercial launch market isn't expanding at a huge rate. The comsat market is reaching saturation while land-based networks are becoming more pervasive. The institutional market is under a lot of pressure too. And new markets will need more than a 20% discount to become viable. In fact, there isn't really much demand for a higher launch rate right now. So, you see, there's very fine balance to be found in the industry, and I applaud SpaceX for trying something new. But this is an industry where technical achievements, no matter how impressive they are from an engineering standpoint, don't always become an industrial success. The success of SpaceX relies on much more than just bringing their rocket back.

It has yet to be seen whether SpaceX can actually keep that promise. Many in the industry have their doubts.

The Stirling engine would be used as a replacement for RTG applications. I'm not sure about its current status at NASA, but it has the huge problem of using moving parts, which means that it is likely to wear and break down. It will be hard to build a Stirling generator that would outlast a conventional RTG in long duration space missions. What are you on about? Hubble had grappling and docking fixtures as well as handrails. Its internal parts were mounted in racks with extendable rails with removable covers and doors. And those replaceable units had their own covers and bezels and fixtures. In fact, there was a lot of extra mass on Hubble to make it serviceable. It would have been a whole lot cheaper and lighter (and therefore easier to replace) if it didn't have all that extra hardware. It also had to be in an orbit that was reachable by the Shuttle, but was not optimal for astronomy. If you didn't have the Shuttle, you would design the satellite so that it would be servicable with whatever vehicle you have. You would fit it with a docking fixture and you could send an Orion with a repair module that would contain EVA equipment, replacement racks, tools, and even an arm if you really need one. You could leave the repair module attached to Hubble for future missions. Citation needed? I don't see anyone working towards orbital space tourism right now, and especially not cheap orbital tourism. Virgin is a quarter-million dollar suborbital roller-coaster ride. Space Adventures has no more seats to sell on Soyuz. Bigelow is still waiting for a proper business model to emerge. That's about it. When you are talking about spending millions of dollars for a seat to orbit, unless you are in the 0.01% who have that level of disposable income, you're always going to need a good reason to send people to space. The Shuttle had one goal after Saturn V and Apollo, which was to provide routine and affordable access to space. It was to be jack of all trades because NASA lacked focus and funding for a specific mission. The problem at NASA was the same as today with SLS: focus on a building the sexiest rocket instead of building the best vehicle for a given task. And why do you have a hard on for wings in space? I'm not saying it was useless. I'm saying that many of the unique things that it did accomplish only existed to justify its existence, but had no real value or could have been done easier or cheaper with other means. The Shuttle was valuable though as an impressive technical achievement and a necessary learning experience.

There are usually at least one or two astronauts watching the docking procedures.

You are confusing the means and the goals. Sending people to space to do plumbing or maintenance work in EVA is not a goal in itself. It's one way of solving a problem. Solving that problem is your goal, and the best way to solve it might or might not involve sending up humans to fix stuff. Having a flashy Buck Rogers spaceship is not a goal in itself. A spaceship exists to perform a task. That task is your goal, and the best way to reach that goal might or might not involve a nice flashy spaceship. Our biggest problem is that we simply haven't found a real purpose for sending people to space in the first place. It's unlikely that spaceflight will ever be "common", because the amount of energy involved in getting stuff into orbit is huge and the equipment for handling that sort of energy will always be expensive and potentially dangerous.

The ISS as it exists was designed to be built by the Shuttle. If you didn't have a Shuttle, you would design it differently. You would dock autonomous modules together like MIR or the Russian segment or you could just launch big monolithic stations like Skylab whenever you need them. The Russians and the Chinese don't need a Shuttle to build their stations, and neither does Bigelow intend to use one to assemble his inflatable modules. If an ISS successor was to be built with SLS, you could put up the entire mass of the ISS in less than 4 launches.

Note that I used the word "practical", not "economical" for my analogy. The rocket itself may be cheap and unreliable, but anything approaching the ISS, however small and automated, is going to be under high scrutiny, because there are human lives involved and billions of dollars of investment. So the actual rendez-vous, docking, and transfer manoeuvers will have to follow the same procedures as any ISS supply craft. Unfortunately, those mission control people don't work for peanuts. That's not how ISS operations go. Progress or ATV are already automated, yet they need to be monitored because things can go wrong and a docking mishap could be catastrophic. You still need someone sitting in the Cupola with their hand over the big red Abort button. You still need a day or two of preparation to rotate the station to its docking/undocking attitude. You still need a team in a mission control center handling tug operations and monitoring the telemetry. The arrival of a supply vehicle, even a fully-automated one, is an "all hands on board" situation for the ISS crew, because safety is critical. Another thing that hasn't been thought out is the actual docking hardware. I'm having a bit of trouble imagining a docking system that can dock a pressurized toroidal payload module and still allow access to the sandwiches that are inside, while remaining simple enough to be dirt cheap, and reliable enough to be used with humans in the loop. It seems to me that putting the payload on top of the rocket would make the design much more straightforward.

Because lots of smaller launches are much cheaper than one big launch every 6 months. You get to share all the fixed costs over more launches and you benefit from economies of scale in manufacturing. Only because Hubble was designed to be serviced by the Shuttle, which made it super expensive. It would have been cheaper to launch 3 replacement Hubbles than to perform all those repair/upgrade missions. If anything, the Hubble program proved that it was not economical to do repairs in space.

DreamChaser is in competition with Dragon 2.0 and CST-100. At least one (probably two) of those competitors will have to go, and DC is a bit of the underdog here, unfortunately.

Which is why the whole Rods from Gods idea isn't very practical. You might as well just make a kinetic weapon out of an ICBM. No need for orbital stations. If they have the means of monitoring incoming projectiles from outer space, then they are also capable of tracking your orbital station and knowing when it's passing overhead.

You'd be better off shooting it upwards by adding the delta-v to your orbital speed to convert it into a high-apogee orbit, then lower the perigee to make it a ballistic trajectory that uses gravity to your advantage. That's smarter that using a huge amount of delta-v to cancel your own speed, and then another huge amount of delta-v to fight against terminal velocity.

Not more than on any other atmosphere-free body. Asteroids in the asteroid belt are in a more or less stable orbit around the sun. Basically, they are all on the same trajectory so the risk of collision between them is minimal.

Thanks for the math... I'm still not convinced that an upmass of 800kg is worth bothering with for ISS operations, and even less for a fuel depot, even if the cost is low. It adds a lot of mission complexity, which also has a cost and an impact on ISS operations. A bicycle is much cheaper than a semi-trailer, but if you need to move 10 tons of apples, it will be more practical to do it with a truck than to do 100 runs with a couple of apples in your pocket, regardless of how cheap the bicycle is. Also, SSTOs tend to have a pretty abyssmal payload fraction. If you can make a cheap expendable SSTO with a 1-ton payload, why couldn't you make a 2 stage rocket with the same technology for twice the cost, but with a 3 ton payload?

Well, math is hard, and I suck at it, which is why I used the word "likely". I'm sure much smarter people will be able to figure it out. The study in the OP doesn't go into much detail about the tug, and I don't thing there are any off-the-shelf upperstages that could serve as a comparison. The Soyuz/Progress SM carries ~2 tons of propellant and only has 390 m/s of delta. It's not a good comparison, because this tug would be much smaller and lighter, but it would also have to be able to do at least twice the orbital changes that are necessary for Soyuz/Progress mission. A closer idea would probably be the Cygnus service module, but I couldn't find the size of its propellant tanks or its dV. To calculate the required dV, we would need to know what they would typically use as a parking orbit, which we don't, but I suspect that it would have to be at a safe distance from the ISS, especially if the rocket has a 30% chance of failure Yeah, maybe I was overestimating with 1 ton of tug propellant for each supply run, but the tug still needs to be refueled, and that will take a significant chunk of the total payload capacity. My point was that the study concentrates on the rocket but ignores the operational cost of the tug, the cost of the incessant manoeuvers and operations that need to be tracked on the ground, the additional ISS docking requirements and the disruption to ISS operations.

Because 1 stage is supposed to be cheaper than 2 stages... I'm not sure that it applies universally, but that's their reasoning. An SSTO doesn't have to be reusable. A reusable doesn't have to be SSTO.