Is inspiration mars more possible than expected? Also how do you think it should be done?

[Beowolf]

I agree there will be people (human beings, or humanity's descendants) living permanently on other worlds. But IMO this plan is doing things in the wrong order. You're asking for a $150 billion investment, and there won't be anything but national pride to show for it afterward. For that kind of money we could have a robotic sample-return mission, and probably still pay for a manned long-term asteroid mission.

But to me, the most important place to spend serious money is to reduce cost/kg into orbit. Get the cost down by 90% to 99% and many impossible missions becomes possible. There are already a host of projects, ranging from Falcon 9R on the practical end to the esoteric Skylon, working to do exactly that. As awesome as it was, I don't want another massive Apollo push just to prove we can. I want a space infrastructure that may take 20 years to develop, but pays off big-time with orbital fuel stations, standardized equipment and proven techniques for space construction, and a couple of big reusable nuclear interplanetary tugs. Even if I won't live to see it.

It's true that eventually humanity needs self-sufficient colonies elsewhere, but that is far beyond our abilities today. A genetically-stable population of humans needs to be over a thousand people! Self-sufficient on Mars means, at the very least, the ability to locate and extract locally every element our bodies and tech use, plus the ability to assemble them on-demand into any of the million different chemicals and isotopes a state-of-the-art Martian colony would need. How's it all powered? Nuclear, perhaps? So they also need an industrial scale uranium enrichment plant. Those are among the largest industrial plants ever built. We gonna ship one to Mars at $100k per kilogram? We simply aren't ready. Give me cheap nano-assemblers or cheap access to orbit and we can talk.

[Nibb31]

But to me, the most important place to spend serious money is to reduce cost/kg into orbit. Get the cost down by 90% to 99% and many impossible missions becomes possible. There are already a host of projects, ranging from Falcon 9R on the practical end to the esoteric Skylon, working to do exactly that.

Even the wildestly optimistic estimates of operational costs of Skylon or reusable Falcon don't come close to a 90% reduction. If you're lucky, you might get a 20% reduction, which would bring the cost of a Falcon 9 launch down from $60 million to $50 million. Also the launch cost is only a small part of the cost of building and operating a spacecraft, so it doesn't translate into huge savings for the customer.

[Beowolf]

Even the wildestly optimistic estimates of operational costs of Skylon or reusable Falcon don't come close to a 90% reduction. If you're lucky, you might get a 20% reduction, which would bring the cost of a Falcon 9 launch down from $60 million to $50 million. Also the launch cost is only a small part of the cost of building and operating a spacecraft, so it doesn't translate into huge savings for the customer.

Oh, I agree. They are steps in a process, not the end result. Sorry if I implied otherwise.

[Rakaydos]

Personally, I think orbital costs and orbital infrastructure are going to inchworm foreward over time.

The Moon required the Saturn 5

Saturn 5 got us Skylab

Skylab maintinance got us the Shuttle

Shuttle built the ISS.

ISS is driving Commercial spaceflight

From here, there's a couple places we can go infrasructure wise- Graveyard Kessler Cleanup, asteroid capture&exploitation, moon-lagrange Kevlar Elevator. these require more expensive, continuing missions bout have strong potential payouts, and will drive launch infrastructure investment- stuff like Airship To Orbit and Microwave Thermal Rockets.

[Northstar1989]

Even the wildestly optimistic estimates of operational costs of Skylon or reusable Falcon don't come close to a 90% reduction. If you're lucky, you might get a 20% reduction, which would bring the cost of a Falcon 9 launch down from $60 million to $50 million. Also the launch cost is only a small part of the cost of building and operating a spacecraft, so it doesn't translate into huge savings for the customer.

Not saying they're realistic, but SKYLON cost-estimates actually predict up to a 95% cost-reduction...

The real game in town for cost-reduction, if you ask me, is going to be Microwave Thermal Spaceplanes...

You get a good enough TWR (2-3 times chemical rockets) and ISP (850-1000 s) for a true HTHL (Horizontal Takeoff Horizontal Landing) spaceplane, and all the benefits of spaceplanes such as using L/D to fight gravity, being able to use air-breathing jets for the initial climb (Thermal Rockets actually present the ULTIMATE in air-breathing efficiency: Thermal Turbojets, which utilize nothing but the atmosphere as propellant, and derive thrust by heating it up and expelling it out the rear of the TTJ... Their ISP in-atmosphere is effectively infinite, as they require no onboard fuel...), and being able to completely re-use your vehicle over multiple missions by landing it back on a runway...

You can use less Microwave Power to get to orbit this way too- a spaceplane can easily take off with a TWR of 0.2 or less, and you can get a much higher Thrust for the same amount of power with a Thermal Turbojet than with a rocket- because you expel a much greater working mass (of air rather than fuel) at a much lower velocity (E = 1/2 mv^2 but Thrust = mass flow * velocity, so if you increase your working-mass you can get MUCH more thrust for the same energy...) Of course, you probably want a higher TWR than this anyways, but the point is that you can get to orbit with maybe 30-40% as much beamed-power with a spaceplane as with a rocket carrying the same payload-mass...

If you *REALLY* wanted to push costs to their lowest, you'd utilize a Suborbital Microwave Thermal Spaceplane- that is one that flies as a plane into a suborbital trajectory (similar to an X-15 or X-37 trajectory: both of which were real life planes that went suborbital using just conventional technology) and then releases a smaller Microwave Thermal Rocket to make orbit...

One advantage of this is that you leave the extra mass of wings, atmospheric intakes, and sophisticated Hybrid Turbojets (that is, engines that can function as both Thermal Turbojets or Thermal Rockets, similar to the way that SABRE can function as either a jet engine or a rocket) behind, and just need to make orbit with a Thermal Rocket already deployed at significant altitude and speed (you can also utilize this as a form of staging- that is the spaceplane fires Thermal Rockets for a period of time to climb higher+faster before releasing the rocket stage, and thus leaves some of the empty fuel tank and engine mass behind...)

The other advantage is that no engine can be designed to do EVERYTHING- not even a Thermal Rocket engine or Hybrid Turbojet... A turbojet doesn't have the same ideal exhaust nozzle as a low-altitude rocket, and a vacuum-optimized Thermal Rocket has a different nozzle-design still (much like with chemical rockets). This allows you to specialize one engine for atmospheric performance and the ability to operate off atmosphere as a propellant, and another to operate best in vacuum. Even the ideal propellants differ. A denser fuel such as Methane is optimal for Thermal Rocket operation in-atmosphere, as the higher Mass Flow Rate leads to reduced atmospheric-compression (Thrust = VacISP * g * Mass Flow Rate - Exit Area * Background Pressure, an equation that describes rocket-performance in-atmosphere that I've been throwing around these forums a lot lately, as it describes why denser propellants suffer less atmospheric-compression, and different altitude require different nozzle designs with greater or lesser Exit Area...) and you can of course pack a lot more mass in Methane into a given sized fuel-tank due to its much higher density; whereas Hydrogen is the ideal propellant for extra-atmospheric thermal rocketry, as its ISP is much higher (850-1000 seconds Vacuum ISP for Hydrogen, vs. 320-360 seconds Vacuum ISP for Methane, but with almost 3 times the thrust for the same amount of beamed-power using Methane...) Combine that with a nozzle-design optimized for vacuum typically having a much larger Exit Area (in order to increase the Exhaust Velocity- and thus the Vacuum Specific Impulse) than one designed for atmospheric performance, and you quickly start to see that a Thermal Rocket designed for atmospheric use looks VERY different (in both propellant choice and nozzle-design) than one designed for vacuum...

Designs of spaceplane that only carry the payload to a suborbital trajectory, which then detaches and uses a rocket to circularize, should be capable of much greater payload-fractions than ones that try and carry their payload all the way to orbit...

Regards,

Northstar

P.S. IF you're interested, I even started a Science Labs thread on suborbital spaceplane launch-architectures...

http://forum.kerbalspaceprogram.com/threads/109810-Suborbital-Spaceplanes

Edited February 7, 2015 by Northstar1989

[Kryten]

If you *REALLY* wanted to push costs to their lowest, you'd utilize a Suborbital Microwave Thermal Spaceplane- that is one that flies as a plane into a suborbital trajectory (similar to an X-15 or X-37 trajectory: both of which were real life planes that went suborbital using just conventional technology) and then releases a smaller Microwave Thermal Rocket to make orbit...

The X-15 was rocket-powered and had to be itself air-launched, and the X-37 is an orbital craft with no propulsion in the atmosphere.

[Kibble]

Designs of spaceplane that only carry the payload to a suborbital trajectory, which then detaches and uses a rocket to circularize, should be capable of much greater payload-fractions than ones that try and carry their payload all the way to orbit...

That's why multiple-stage rockets were developed.

[Northstar1989]

That's why multiple-stage rockets were developed.

Exactly. And that's one of the reasons that a spaceplane (which has much lower mass-fractions than a rocket, thanks to wings, intakes, etc.) would operate best as a first stage rather than a SSTO...

Regards,

Northstar

- - - Updated - - -

The X-15 was rocket-powered and had to be itself air-launched, and the X-37 is an orbital craft with no propulsion in the atmosphere.

Number mess-up. The X-15 was one of the planes to break the Karman Line. I believe I was thinking of a SR-71 (Blackbird) flight that did it the other planes that did it, however briefly? (I'll have to check what the other plane was I was referring to...)

Regards,

Northstar

- - - Updated - - -

The X-15 was rocket-powered and had to be itself air-launched, and the X-37 is an orbital craft with no propulsion in the atmosphere.

Number mess-up. The X-15 was one of the planes to break the Karman Line. I believe I was thinking of a SR-71 (Blackbird) flight that did it the other planes that did it, however briefly? (I'll have to check what the other plane was I was referring to...)

EDIT: Probably not the SR-71. I'll remember it eventually. Anyways, the point was that suborbital planes have been done before. Multiple times.

Regards,

Northstar

[Kryten]

Number mess-up. The X-15 was one of the planes to break the Karman Line. I believe I was thinking of a SR-71 (Blackbird) flight that did it the other planes that did it, however briefly? (I'll have to check what the other plane was I was referring to...)

The SR-71 altitude record (and record for anything in level flight) is just under 30km. The record for altitude reached in a zoom climb by an air-breathing aircraft is about 38km, set by a modified MiG-25; still less than halfway to the Karman line. The only aircraft to have ever breached it are X-15 and SS1, both needing air-launch and using rocket engines.

[Northstar1989]

The SR-71 altitude record (and record for anything in level flight) is just under 30km. The record for altitude reached in a zoom climb by an air-breathing aircraft is about 38km, set by a modified MiG-25; still less than halfway to the Karman line. The only aircraft to have ever breached it are X-15 and SS1, both needing air-launch and using rocket engines.

Hmmm.... Maybe I was wrong?

Anyways, SS1 and X-15 is still more than one! And I'm amazed how my point about Microwave Beamed Power has gone unnoticed yet again...

Did I mention the same power-transmission system is also highly useful for orbital propulsion (It's a MUCH lower-mass way to power high-thrust electric thrusters than a nuclear reactor...) and Propulsive Fluid Accumulators?

Regards,

Northstar

[Rakaydos]

Microwave thermal launchers are one of the next steps for launchers, but first we need the next step in "reasons to go to space", to drive launch infrastructure development.

A lunar elevator will do it, as will asteroid mining. Once there's profit to be made going to space cheaply on your own dime, well, "if you build it they will come."