Hubble repair from ISS

[kk434]

I wonder it there is a possibility to undertake a Hubble repair mission from the ISS, there is a 23 degree difference in thier orbits so you need some delta V go from one to the other. One forum sugests 5 km/s. If you only want to send a couple of astronauts in thier spacesuits and some spare parts to the Hubble 5 km/s delta V can be done with a small rocket. This is just speculation, all other spacewalks have been close to the ISS and sending astronauts this far is very risky but developing that capability would be a great leap forward. And Hubble is such a great icon that politicians would be more generous in provideing funds too such an endevour.

http://www.physicsforums.com/archive/in ... 60706.html

 

[vattas]

Do you realize, that 5km/s is delta V is not far away from getting from the ground to LEO (delta V 8km/s) ? And don't forget that you also need to return, so that's another 5km/s.

 

[kk434]

Yes I know but launching from the ISS you dont need a heavy heat shield, landing system and others. So a craft launched from ISS might only be 1 tone and not 300 tonne like a ELV. 5 km/s delta V for a 1 tone craft may not be such a big problem.

 

[oldAtlas_Eguy]

An example of what it takes to get 5 km/s delta V for a payload of 10,000 kg, that equivelent to a Falcon 9 second stage. A Falcon 1 second stage weighs 8000 kg and only would provide the capability to change orbit of a 1000kg payload. Thats a Falcon 9 payload just for the stage and propelant to do the inclination change for 1000kg payload. You could use that same falcon 9 to send a 9,000 kg payload directly to Hubble.

 

[DarkenedOne]

I wonder it there is a possibility to undertake a Hubble repair mission from the ISS, there is a 23 degree difference in thier orbits so you need some delta V go from one to the other. One forum sugests 5 km/s. If you only want to send a couple of astronauts in thier spacesuits and some spare parts to the Hubble 5 km/s delta V can be done with a small rocket. This is just speculation, all other spacewalks have been close to the ISS and sending astronauts this far is very risky but developing that capability would be a great leap forward. And Hubble is such a great icon that politicians would be more generous in provideing funds too such an endevour.

http://www.physicsforums.com/archive/in ... 60706.html

The other guys are right kk434. The delta-v requirements would make it unpractical and definitely uneconomical for a chemically propelled spacecraft from the ISS. The rocket eq tells us that such a spacecraft would have to be around 90% fuel by weight even when using LH2/LOX.

It is definitely practical though if you had thrusters with a higher ISP. Existing ion propelled spacecraft like the DAWN interplanetary probe could make the journey with only about 10% of its weight being fuel. The problem with that approach is that it would likely take months to get there and months to get back. This time period is acceptable to unmanned craft, but not so for manned spacecraft.

Now if you could use some type of high impulse, high thrust technology like nuclear-thermal than you would definitely be able to do it.

 

[scottb50]

I wonder it there is a possibility to undertake a Hubble repair mission from the ISS, there is a 23 degree difference in thier orbits so you need some delta V go from one to the other. One forum sugests 5 km/s. If you only want to send a couple of astronauts in thier spacesuits and some spare parts to the Hubble 5 km/s delta V can be done with a small rocket. This is just speculation, all other spacewalks have been close to the ISS and sending astronauts this far is very risky but developing that capability would be a great leap forward. And Hubble is such a great icon that politicians would be more generous in provideing funds too such an endevour.

http://www.physicsforums.com/archive/in ... 60706.html

The other guys are right kk434. The delta-v requirements would make it unpractical and definitely uneconomical for a chemically propelled spacecraft from the ISS. The rocket eq tells us that such a spacecraft would have to be around 90% fuel by weight even when using LH2/LOX.

It is definitely practical though if you had thrusters with a higher ISP. Existing ion propelled spacecraft like the DAWN interplanetary probe could make the journey with only about 10% of its weight being fuel. The problem with that approach is that it would likely take months to get there and months to get back. This time period is acceptable to unmanned craft, but not so for manned spacecraft.

Now if you could use some type of high impulse, high thrust technology like nuclear-thermal than you would definitely be able to do it.

It could be done with highly elliptic orbit, change the inclination at the apex of the orbit and it is possible with existing technology. Unless you consider Nuclear-thermal detonating bombs against a fixed plate it would actually produce high ISP similar to that used by Ion thrusters, not a kick in the pants thrust.

Changes in inclination are done by spy satellites routinely, the X-37 did it just recently.

 

[oldAtlas_Eguy]

Vo – orbit velocity
Delta_i - delta inclination in radians
deltaVi - delta V needed for inclination change
deltaVi=SQRT((Vo*(1-cos(Delta_i)))^2+(Vo*sin(Delta_i))^2)

and using the calculator http://www.rclsoftware.org.uk/gravel/orbits.html
with 5.9737e24 for the mass of earth entry and 6378100 added to the meters of orbital height of ISS of 350000 and the orbital height of Hubble of 600000 gives the transfer delta V values. Then use the same value for apogee and perigee will result in a circular orbit velocity value for ISS and Hubble. Then simple subtraction gives the delta V for getting to the transfer orbit and then to circularize to Hubble. Add all three delta V’s to get all of the delta V to get to hubble from ISS.

The end result is that a delta V of 4085 m/s is about the best that can be done.

 

[kk434]

Sounds like going to Hubble from ISS is a bad idea, way too much delta V. Maybe permanently repositioning Hubble so it is close to ISS is a better idea. Hubble already has a attachment so a booster can deorbit it in to the pacific, why not atach a bigger one and bring it close to the ISS?

 

[MeteorWayne]

Changes in inclination are done by spy satellites routinely, the X-37 did it just recently.

Uhhh, no it didn't. 40 degrees before, 40 degrees after....

 

[DarkenedOne]

The other guys are right kk434. The delta-v requirements would make it unpractical and definitely uneconomical for a chemically propelled spacecraft from the ISS. The rocket eq tells us that such a spacecraft would have to be around 90% fuel by weight even when using LH2/LOX.

It is definitely practical though if you had thrusters with a higher ISP. Existing ion propelled spacecraft like the DAWN interplanetary probe could make the journey with only about 10% of its weight being fuel. The problem with that approach is that it would likely take months to get there and months to get back. This time period is acceptable to unmanned craft, but not so for manned spacecraft.

Now if you could use some type of high impulse, high thrust technology like nuclear-thermal than you would definitely be able to do it.

It could be done with highly elliptic orbit, change the inclination at the apex of the orbit and it is possible with existing technology.

Yes it is true that plane changes are a hell of a lot cheaper if the change is made at the apogee of a elliptical orbit. However you still have to change the orbit and that still requires significant delta-v.

Secondly I am talking about economical not just possible. Yes it is possible to build a spacecraft that travels to the Hubble from the ISS and back, however as it has not been done and will not be done using traditional chemical propulsion, because chemical propulsion has to low ISP.

Unless you consider Nuclear-thermal detonating bombs against a fixed plate it would actually produce high ISP similar to that used by Ion thrusters, not a kick in the pants thrust.

Nuclear thermal would work just fine.

Changes in inclination are done by spy satellites routinely, the X-37 did it just recently.

Small ones yes. Large ones no. Inclination changes are among the most expensive maneuverer that a spacecraft could perform especially those in LEO.

 

[kk434]

Today SDC an ISS manager wants a telescope close to the ISS,

"Leckrone has his own dream project.

He'd like to put a new telescope in orbit near the space station, in a similarly high-inclination orbit, that would be suitable for searching out habitable exoplanets yet also be in a position to receive continual upgrades and maintenance by astronauts from the station.

In effect, station crew would serve as garage mechanics for such a telescope.

"If people start thinking creatively," Leckrone said, "you can think of a lot of things to be done on station.""

Why not try to reposition Hubble so it is close to the ISS?