Its not the space shuttle, nor is it intended to be.
The space shuttle can launch 20ish tons to LEO. But what if youre just going to the space station for a crew transfer? Its about as economical as taking a semi-truck down to the drugstore instead of a 4-cylinder coupe.
We dont always needs huge payloads. The other interesting idea with this concept is that this vehicle is being designed to be launch from current launch vehicles. Given the current budgetary situation, doing more with less is vital.
a) de-orbit into the sun. Nice recycle/reuse spin i.e. we get some of the energy back as sunlight; or
Deorbiting into the earth requires maybe 1 km/s of a change in velocity. Deorbiting into the sun would require something like 25 km/s or more of a change in velocity. Actually, the easiest way to get to the sun from the earth is to fly by jupiter and use its gravity to kick you into it, but thats still way more than 1km/s.
b) de-orbit into deep space. Nothing says "There's other intelligent life" to an alien scientist like a slightly used space telescope careening away from an overlooked solar system.
Escaping from the earth's gravity, and then the suns gravity requires a lot of propellant as well.
In short, policitians only like a space program that doesnt cost a lot of money. If you want NASA to have more funding, you need to talk to your representatives, no NASA.
As for propulsion, I don't see any great need for higher power nuclear sources. The outbound thrust is the hard part. If we need high ISP for that, use solar-powered ion propulsion (like DS1 or any recent comsat station-keeping system), and run it while the probe is diving past Venus. You could spend a year or so close to the Sun building velocity before you head out.
Nuclear Electric Propulsion is useless for a planetary insertion burn, where you need your delta-V over a couple of hours. So that's going to be a N2O4/N2H4 rocket for the forseeable future (and it'll burn a good chunk of the mission mass).
Low thrust missions are fundamentally different from (nearly) impulsive missions. The trajectory is designed such that the excess velocity at the target planet is at or near zero, such that the propulsion system is capable of performing the insertion maneuver, all the while using less propellant than a chemical propulsion system. Low-thrust missions generally take longer than chemical missions, but can accomodate much more payload due to the low propellant usage.
The only bit left is maneuvering thrust while in Jupiter (or Saturn) orbit. Here high ISP can extend the mission life, which is good. Surely they can get by with RTG-powered ion thrust, with N2O4/N2H4 used as a backup and for radical course changes.
RTG-powered ion thrusters generally wont have a high Isp unless the spacecraft is exceptionally light. With a low power, high thrust combination, thrust acceleration is extremely low, which in turn causes "gravity losses" to increase, which eats into the low-propellant benefit that the ion engines are supposed to give you. For light spacecraft it may not make a difference. If you wish to send a large payload, it will.
RTGs are for power generation, not propulsion. You could use them to power an electric propulsion system (Ion engines), but the propellant for such a system is inert gas (xenon or krypton) and doesnt pose much of an environmental risk.
RTG's yield such little power that using them for propulsion only makes sense for very light spacecraft, where you can do most of the energy input using the launch vehicle.
Nuclear Electric Propulsion (using a reactor) can generate much more power but is also heavier. So you cant boost it to as high an energy with the launch vehicle, since its heavier, but for sending large payloads to the outer planets, its the only option.
I disagree with the above link's conclusions that nuclear reactors in space have no purpose. Our civilization simply has no other way to get large payloads to distant planets, unless you want to launch several saturn V's into earth orbit and do the assembly of your spacecraft there.
RIAA-loving CEO: Sure...sell the songs for $0.99. Noone will buy them, people prefer a CD, plus we can justify a larger profit margin when we sell CD's.
RIAA-loving CEO: Amazing...people seem to actually prefer downloading their music. Increase the profit margin on it!
When NASA gets the kind of funding it did during the 60's we'll see development of full programs in under 10 years. Even so, a suborbital demo flight of CEV in 3 years is a pretty quick schedule, considering the vehicle has to be extensible to bother LEO and deep space applications.
And hasnt been for some time. All satellites put up for private enterprise are launched (typically) on Lockheed Martin (Atlas) or Boeing (Delta) launch vehicles.
Burt Rutan, who IMHO is an aeronautical genious, and his team took years to do this. Is the one year cycle enough to do this right?
Furthermore, having prizes for things like "most passengers" just smacks of safety issues.
Even SpaceshipOne was almost lost on one of its flights. This isnt trivial, things can and will go wrong, and its a very unforgiving environment.
Now if people accept the risks and are willing to go regardless, I respect that. But what I dont want is a bunch of bad press for space travel, and resulting overregulation and fear among the public, resulting from a slew of fatalities at the X Prize Cup.
I agree with boredman. It sounds corny, but we control our destiny. If we want the future to be bright, we have to make it so.
Especially the technology minded/geeky/typical slashdot readers. Many of us are in fields that will have a strong effect on the future. Lets hope that effect is positive for humanity.
We need goals. I want to live my life trying to do something big for humanity. Too many people these days see their job as a necessary evil to getting a paycheck.
explore options to create a university-based virtual space academy" for training the next generation technical work force.
This may be my favorite part. Itll will be difficult to replace the upcoming flood of retirements with so few students majoring in aerospace engineering (emphasis on space) these days. Giving NASA an academy from which to draw potential engineers, astronauts, and technicians would give it a pool of driven young minds.
Ion propulsion typically doesnt work in an atmosphere. Let alone that its going to have to overcome gravity and the drag of the upper atmosphere to get its payload into orbit.
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Science isn't defended via cross-examinations.
Science is defended via hypothesis and experimentation.
Its not the space shuttle, nor is it intended to be.
The space shuttle can launch 20ish tons to LEO. But what if youre just going to the space station for a crew transfer? Its about as economical as taking a semi-truck down to the drugstore instead of a 4-cylinder coupe.
We dont always needs huge payloads. The other interesting idea with this concept is that this vehicle is being designed to be launch from current launch vehicles. Given the current budgetary situation, doing more with less is vital.
Specific impulse is usually "normalized" by g at earth sea level.
Exhaust Velocity = g * Isp
Therefore, Isp is uaually listed in units of seconds.
Hey, thats text!
Its you.
Space exploration is a drop in the bucket compared to other components of a nations budget.
While I agree that basic science is good, Hubble has already exceeded its expected lifetime. Everything we get now is a bonus.
Also, we can put up a new one with better features for the same amount of money.
a) de-orbit into the sun. Nice recycle/reuse spin i.e. we get some of the energy back as sunlight; or
Deorbiting into the earth requires maybe 1 km/s of a change in velocity. Deorbiting into the sun would require something like 25 km/s or more of a change in velocity. Actually, the easiest way to get to the sun from the earth is to fly by jupiter and use its gravity to kick you into it, but thats still way more than 1km/s.
b) de-orbit into deep space. Nothing says "There's other intelligent life" to an alien scientist like a slightly used space telescope careening away from an overlooked solar system.
Escaping from the earth's gravity, and then the suns gravity requires a lot of propellant as well.
In short, policitians only like a space program that doesnt cost a lot of money. If you want NASA to have more funding, you need to talk to your representatives, no NASA.
1992 called, and wants its joke back.
Well the jerk store called...and they're running out of you!
-obligatory Seinfeld reference
As for propulsion, I don't see any great need for higher power nuclear sources. The outbound thrust is the hard part. If we need high ISP for that, use solar-powered ion propulsion (like DS1 or any recent comsat station-keeping system), and run it while the probe is diving past Venus. You could spend a year or so close to the Sun building velocity before you head out.
Nuclear Electric Propulsion is useless for a planetary insertion burn, where you need your delta-V over a couple of hours. So that's going to be a N2O4/N2H4 rocket for the forseeable future (and it'll burn a good chunk of the mission mass).
Low thrust missions are fundamentally different from (nearly) impulsive missions. The trajectory is designed such that the excess velocity at the target planet is at or near zero, such that the propulsion system is capable of performing the insertion maneuver, all the while using less propellant than a chemical propulsion system. Low-thrust missions generally take longer than chemical missions, but can accomodate much more payload due to the low propellant usage.
The only bit left is maneuvering thrust while in Jupiter (or Saturn) orbit. Here high ISP can extend the mission life, which is good. Surely they can get by with RTG-powered ion thrust, with N2O4/N2H4 used as a backup and for radical course changes.
RTG-powered ion thrusters generally wont have a high Isp unless the spacecraft is exceptionally light. With a low power, high thrust combination, thrust acceleration is extremely low, which in turn causes "gravity losses" to increase, which eats into the low-propellant benefit that the ion engines are supposed to give you. For light spacecraft it may not make a difference. If you wish to send a large payload, it will.
RTGs are for power generation, not propulsion. You could use them to power an electric propulsion system (Ion engines), but the propellant for such a system is inert gas (xenon or krypton) and doesnt pose much of an environmental risk.
RTG's yield such little power that using them for propulsion only makes sense for very light spacecraft, where you can do most of the energy input using the launch vehicle.
Nuclear Electric Propulsion (using a reactor) can generate much more power but is also heavier. So you cant boost it to as high an energy with the launch vehicle, since its heavier, but for sending large payloads to the outer planets, its the only option.
I disagree with the above link's conclusions that nuclear reactors in space have no purpose. Our civilization simply has no other way to get large payloads to distant planets, unless you want to launch several saturn V's into earth orbit and do the assembly of your spacecraft there.
RIAA-loving CEO: Sure...sell the songs for $0.99. Noone will buy them, people prefer a CD, plus we can justify a larger profit margin when we sell CD's.
RIAA-loving CEO: Amazing...people seem to actually prefer downloading their music. Increase the profit margin on it!
When NASA gets the kind of funding it did during the 60's we'll see development of full programs in under 10 years. Even so, a suborbital demo flight of CEV in 3 years is a pretty quick schedule, considering the vehicle has to be extensible to bother LEO and deep space applications.
And hasnt been for some time. All satellites put up for private enterprise are launched (typically) on Lockheed Martin (Atlas) or Boeing (Delta) launch vehicles.
So how long did it take to make it to the cache? Anyone pay close enough attention?
Burt Rutan, who IMHO is an aeronautical genious, and his team took years to do this. Is the one year cycle enough to do this right?
Furthermore, having prizes for things like "most passengers" just smacks of safety issues.
Even SpaceshipOne was almost lost on one of its flights. This isnt trivial, things can and will go wrong, and its a very unforgiving environment.
Now if people accept the risks and are willing to go regardless, I respect that. But what I dont want is a bunch of bad press for space travel, and resulting overregulation and fear among the public, resulting from a slew of fatalities at the X Prize Cup.
Its also suborbital. It'll be interesting to see the first private spacecraft to make it to LEO, and the cost incurred.
Then comparisons with the space shuttle will be somewhat more valid.
I agree with boredman. It sounds corny, but we control our destiny. If we want the future to be bright, we have to make it so.
Especially the technology minded/geeky/typical slashdot readers. Many of us are in fields that will have a strong effect on the future. Lets hope that effect is positive for humanity.
Agreed. Mod Parent Up.
We need goals. I want to live my life trying to do something big for humanity. Too many people these days see their job as a necessary evil to getting a paycheck.
explore options to create a university-based virtual space academy" for
:)
training the next generation technical work force.
This may be my favorite part. Itll will be difficult to replace the upcoming flood of retirements with so few students majoring in aerospace engineering (emphasis on space) these days. Giving NASA an academy from which to draw potential engineers, astronauts, and technicians would give it a pool of driven young minds.
Can the Starfleet Academy be far behind?
Ion propulsion typically doesnt work in an atmosphere. Let alone that its going to have to overcome gravity and the drag of the upper atmosphere to get its payload into orbit.
I wish them well, but I'm not holding my breath.
They hold the purse strings. Without the support of congress, NASA couldn't go.
Thanks for the creativity.
This headline apparently written by the Church Lady
Bart: I feel like I'm going to die, Lisa
Lisa: We're all going to die, Bart.
Bart: I meant soon.
Lisa: So did I.
Its now the Glenn Research Center (ironically enough)