The thread for space cadets!

[Glassfan]

Just like those Rocket landings in the old 1950's SciFis. Just like the Apollo landings, but with a computer instead of a man. We'll be able to land pilotless vehicles on the moon or the planetoids. Very useful...

 

[hobbsyoyo]

Just like those Rocket landings in the old 1950's SciFis. Just like the Apollo landings, but with a computer instead of a man. We'll be able to land pilotless vehicles on the moon or the planetoids. Very useful...

I agree but I have to point out that the Apollo landers didn't have to deal with an atmosphere which makes the whole process that much more difficult.

I'm not sure though that the techniques developed for the F9FT landing will carry over much to unmanned probes in a significant way. F9FT used GPS (and probably active homing beacons) to plop down exactly where it was told. We won't have that on other moons or planetoids or planets. Landing enormous vehicles is useful in and of itself but actually getting enormous (and fully or partially fueled) vehicles to other planets is the bigger problem in the first place IMHO. And NASA has managed to nail the process of (essentially) precision landings on other planets, though their landers are dwarfed by the size of the F9FT first stage.

 

[Glassfan]

It was my understanding that a peculiar difficulty on the moon and other bodies lacking an atmosphere, is that the more efficient glider/shuttle landing (what's the term for that Señor?) is not possible, and that this vertical landing technique will be invaluable.

Presumably, the moon and the more important colonies and bases will eventually acquire their own array of satellites, including GPS.

 

[Glassfan]

I agree but I have to point out that the Apollo landers didn't have to deal with an atmosphere which makes the whole process that much more difficult.

Just occurred to me, another good reason for manned flight - first landing on these rocks will always require human piloting skills.

 

[hobbsyoyo]

It was my understanding that a peculiar difficulty on the moon and other bodies lacking an atmosphere, is that the more efficient glider/shuttle landing (what's the term for that Señor?) is not possible, and that this vertical landing technique will be invaluable.

I think you are referring to aerobraking, where a vehicle uses the atmosphere of a planet to slow itself down before it lands. Paradoxically, aerobraking can be both more and less efficient, depending on how it is used.

For example, the Space Shuttle was able to achieve pinpoint landing accuracy with a huge amount of cross-range potential (i.e. it could begin re-entry thousands of miles from where it landed whereas most capsules make it maybe a few hundred klicks at best). However, to do this, it drug along wings that weighed many tons and were completely useless for everything except landing.

In addition to the weight of the wings (which cut significantly into payload mass - the SS stack could deliver 100 tons to orbit, comparable to a Saturn V but only 20 tons of actual payload thanks to the structural deadweight of the wings), they also made the vehicle significantly more dangerous. There was no realistic option to abort a mission once the SRB's were lit and there was no realistic way for the crew to eject. Unlike capsules which are fitted with escape rockets, the very nature of the shuttle (i.e. it's wings) made this feature impossible. As a direct result, the 7 astronauts on the final flight of the Challenger all died when the stack blew up - whereas with a conventional pod they could have survived.

So, to use these nifty wings for a precision landings, they gave up critical safety features and multiple tons of payload capacity. This is why many people in the aerospace community view the shuttle as an impractical failure and a mistake and is also a large part of why NASA's next manned rocket, the SLS, features a conventional capsule design even though it recycles a ton of Space Shuttle hardware.

On the flip side, capsules also use aerobraking and it saves them from having to bring along an enormous amount of fuel to decelerate. Advances in lifting body technology and computer guidance have also allowed them to get fairly accurate (compared to Apollo) in where they touch down though not to the exact meter or anything like the Shuttle.

Note that a very important feature of the F9FT first stage was the use of grid fins for steering. It doesn't carry enough cold-gas N2 to steer the whole way down and to do so would cost a ton of weight. So even the F9FT won't work on a place like the moon without extensive modification.

To make the decision tree even more complicated, on a planet like Mars, the atmosphere is thick enough to cause a lot of heating of the entry vehicle but not thick enough to allow a large payload to fully slow down. That's why for Curiosity, NASA opted to use the Skycrane approach which used a bunch of rockets to slow down the rover and gently put it down. This approach is broadly similar to the Apollo landers approach and is why I say NASA pretty much already has this technology and techniques nailed. However, landing an F9FT (which is many times more massive) is much harder, but given the use of steering fins on the F9FT means it's not directly applicable to the Moon or airless bodies. All in all, its and impressive feat and will certainly push the technology forward.

Sorry for the long-winded explanation.

Presumably, the moon and the more important colonies and bases will eventually acquire their own array of satellites, including GPS.

True story! In fact, one of NASA's next Mars orbiters is carrying along a collection of CubeSats it will deploy on-orbit that will form an ad-hoc communications network covering much of the planet.

Just occurred to me, another good reason for manned flight - first landing on these rocks will always require human piloting skills.

I'm totally for manned flight but I don't think this is true. NASA has put down several probes on Mars that didn't require human intervention and the first landings on the Moon were also unmanned and automated.

 

[Glassfan]

NASA has put down several probes on Mars that didn't require human intervention and the first landings on the Moon were also unmanned and automated.

True. But on the other hand, they've had some dramatic failures (Mars Climate Orbiter and others) do to miscalculations and, lets face it, NASA isn't what it once was. An experienced human pilot can adjust and compensate for unexpected contingencies.

 

[Michkov]

True. But on the other hand, they've had some dramatic failures (Mars Climate Orbiter and others) do to miscalculations and, lets face it, NASA isn't what it once was. An experienced human pilot can adjust and compensate for unexpected contingencies.

I'd count a programming error as human failure though, a computer is only as good as the program you put in after all.

 

[Glassfan]

We have relatively sophisticated automated landing programs on passenger jets and military planes already, but they're not yet considered reliable enough to safely land human cargo, so you still need human pilots. That may change in years to come with AI, but then, it will be their world not ours.

In the interim (while we are still in control), I would envision orbital platforms with human drone pilots landing ships onto planetary surfaces.

 

[uppi]

We have relatively sophisticated automated landing programs on passenger jets and military planes already, but they're not yet considered reliable enough to safely land human cargo, so you still need human pilots. That may change in years to come with AI, but then, it will be their world not ours.

In the interim (while we are still in control), I would envision orbital platforms with human drone pilots landing ships onto planetary surfaces.

I have the impression that the autolanding systems are certainly considered reliable enough for human cargo, so that they can be used even when the pilot is unable to see anything. But for obvious reasons, the pilots are not very fond of it, so they do not use it if they do not have to. And as NASA has shown, they are good enough for automatic landings on Mars most of the time.

The thing is, sending a human pilot increases the cost of the mission by at least an order of magnitude. So if the autopilot is reliable most of the time it would still be cheaper to just send multiple drones instead of one vessel with a human pilot.

 

[Thorgalaeg]

In fact we have reliable and totally automatic landing systems which are used thousands of times everyday worldwide to autoland liners carrying millions of passengers (with human crew supervision of course). However it is not about the plane landing automatically anywhere, it requires an airport equiped with cat III ILS, which is a big and complex set of antennas and radio beacons. So it is more about the airport than about the plane, not to apply in the case of landing at moon or mars till we have international (or interplanetary) airports there. Obviously we will have unthinkable dron and guidance tech for then though.

 

[hobbsyoyo]

I have the impression that the autolanding systems are certainly considered reliable enough for human cargo, so that they can be used even when the pilot is unable to see anything. But for obvious reasons, the pilots are not very fond of it, so they do not use it if they do not have to. And as NASA has shown, they are good enough for automatic landings on Mars most of the time.

The thing is, sending a human pilot increases the cost of the mission by at least an order of magnitude. So if the autopilot is reliable most of the time it would still be cheaper to just send multiple drones instead of one vessel with a human pilot.

I would argue that a robotic landing probe can provide an order of magnitude less science than a human could.

Yeah, it's going to cost an order of magnitude more to send a human but the added incremental cost of equipping that human with all the tools s/he needs to do a proper investigation of an area is going to be very small next to the total. Plus a human on the ground has the best tools (hands, eyes and brain) that robots lack (huge difference between us looking at a screen of what a robot can see with a camera versus us being there with our own eyes, etc).

Adding the gear to a robot to do the same kind of science as a human could do would be much more than an incremental cost to a robotic mission - every single additional instrument adds millions and millions to the budget and raises the complexity of the mission enormously.


But all of this is entirely beside the point of human versus autopilot. But a human pilot could do a lot of stuff the autopilot can't do once they are on the ground.

 

[BvBPL]

In a week, the Earth will be at perihelion. As the Earth follows an elliptical orbit, it's orbital speed is not consistent throughout the year. What is the orbital speed of the Earth at perihelion and aphelion and when is the orbital speed fastest and slowest?

Also, is there a difference in the arc of the elliptical at perihelion and aphelion?

 

[Michkov]

At Perihelion the speed is the fastest vice versa the slowest at Apohelion. Read up on Keplers laws to see why. Cant find numbers on the speed but you should be able to calculate them using above mentioned laws.

I dont understand the last question though? What do you mean by elliptical?

 

[BvBPL]

I don't have the math to accurately describe my second question so bear with me.

Imagine you have an elliptical running from -10x to +10x in both cases at 0y. At -8x say the y values run from -5y to +5y. At +8x the y values run from -4y to +4y. So there is a different rate of increase in the y values at either end of the elliptical.

Does this happen with the Earth's orbit? Does the rate of change in y differ moving from the perihelion to the aphelion? How about along the z axis?

 

[Michkov]

I don't have the math to accurately describe my second question so bear with me.

Imagine you have an elliptical running from -10x to +10x in both cases at 0y. At -8x say the y values run from -5y to +5y. At +8x the y values run from -4y to +4y. So there is a different rate of increase in the y values at either end of the elliptical.

Does this happen with the Earth's orbit? Does the rate of change in y differ moving from the perihelion to the aphelion? How about along the z axis?

OK now I understand. What you are asking for is the curvature of the ellipse (elliptical seems to be some kind of exercise equipment according to google). The curvature, ie how much the path deviates from a straight line, is at its maximum at both Apo/Perihelion. With the minimum 90° further along the orbit.

Maybe this picture helps


The difference in distance at peri/apohelion comes from the planet revolves around on of the focii of the ellipse not the origin.

 

[BvBPL]

Do you know if that picture is to scale?

Never mind, it seems to be hypothetical.

 

[hobbsyoyo]

Busy few weeks in the space community!

Blue Origin re-launched and landed their New Shepard suborbital capsule and booster. This was the second flight and vertical landing for the same rocket, which is super awesome.


Link to video.

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SpaceX successfully launched the Jason-3 satellite and attempted a barge landing. Unfortunately, one of the landing legs failed to lock and though they managed to land it, it soon tipped over and exploded. This was not a re-flight of the booster that pulled off the land-landing previously (which was an upgraded 'Full Thrust' Falcon 9) but rather the last flight of the Falcon 9 v1.1 booster which is now retired in favor of the Full Thrust variant.


Link to video.

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India also successfully launched a satellite to help complete a regional GPS system they are building. ISRO is really coming along as a world-class space agency and I can't wait for them to start launching astronauts.

 

[hobbsyoyo]

Orbital, Sierra Nevada, SpaceX win NASA commercial cargo contracts

SNC was previously passed up when they offered the Dream Chaser to NASA for crew runs to the ISS. The space division of the company began to fall on some hard times thereafter but they now have successfully convinced NASA they are a good option for resupply missions and won a resupply contract.

Winning the contract means they will move forward with an unmanned version of their Dream Chaser craft. It also triggered a contractual agreement with Airbus wherein the European company will invest in SNC and help develop equipment and a service module for the Dream Chaser. There is also talk of launching the Dream Chaser on Arianespace rockets now and even possible development of a manned Dream Chaser for use by the ESA - which has long pursued a mini-shuttle but always stopped short of finishing their projects. The proposed service module is the unit hanging off the back-end of the Dream Chaser (with the solar panels) in the illustration above.

Before the announcement, there had been discussion that NASA might drop either SpaceX or Orbital ATK from the second round of the commercial resupply mission in favor of newcomers. The logic was that these CRS contracts really helped SpaceX and Orbital ATK introduce new rockets/capsules/systems that they can now use for other projects and there was a desire to spread that CRS money around to help other companies develop more rockets/capsules/systems. This would in the long run foster innovation in the space industry, provide redundancy in the case of launch vehicle failures and in general push the American space industry forward.

As it turned out, NASA was given more money by Congress than anticipated (for once!) and this allowed them to continue supporting SpaceX and Orbital ATK while also bringing on board a newcomer, SNC.

Very cool all around and good news for job seekers like myself!

 

[r16]

this SNC thing is weirdly has been allowed to be bought by a Turkish couple in the American thing for creating a NEW , TWICE BETTER Turkey . You might find yourself out of work in a most unconvenient time .

 

[hobbsyoyo]

The couple that owns SNC have lived in the US since the 70's/80's and have owned the company since the 90's (IIRC). They do have some contracts to produce jets in Turkey but I don't see any likelihood that they will pull SNC out of America, ever.

If that's what you're getting at.

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There was for a while a ban on the use of Russian engines to launch US military satellites. The principal company affected was ULA as their Atlas V rocket uses RD-180 engines from Russia. The company was allowed to use the engines they had already imported for launching military satellites and was also allowed to continue to import additional engines for non-military use, but for military use they were limited to the stockpile they had on hand.

Additionally, the US government has at various times given ULA millions of dollars to study building domestic copies of the RD-180 engines or swapping them for other US-made engines. They did the studies but then failed to act on their own findings and recommendations. They likely did this because at the time, they were the sole authorized provider of launch vehicles for military satellites. The company is also set up as a joint venture between Lockheed Martin and Boeing, which have seen fit to essentially use ULA as a cash cow and have provided minimal investment in it. So they had no interest in pursuing a domestic replacement for the Russian engines as that would cost them money.


However, SpaceX was recently certified to fly military satellites. Following that was the first actual competition for military satellite launches. In response to this new competition and the engine ban, ULA flatly refused to compete for the launches - they pulled out of the competition entirely in a move that shocked the industry. To make things worse, they even re-assigned engines that had been set aside for military launches to commercial launches, deliberately undercutting their supply of engines.

Shortly thereafter, a congressman (who happens to have a ULA plant in his district) managed to put a rider in the defense spending bill that lifted the ban on Russian engines. ULA essentially tried to play chicken with the US government/military and it seemed they had won.

In response, John McCain and his allies are pushing to re-introduce the ban and are likely to succeed. To make it even worse, the Air Force is now considering terminating the $800million/year subsidy that they give to ULA (that literally is used to keep their doors open).

In other words, ULA gambled that they could game the government procurement system and are on the verge of losing big time.

Ugh, it's a shame there is so much political intrigue surrounding the launch industry.