Author Topic: Starship for outer planets and beyond  (Read 41511 times)

Offline SteveJ

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Starship for outer planets and beyond
« on: 06/13/2020 09:10 pm »
How much payload could a stripped down, expendable version of SS launch on an interstellar voyage, and what escape velocity could it achieve?  What could SS do on its own, vs. carrying one or more upper stages to boost the spaceship?

If we need to define the question more tightly, then assume we wanted a 1200 kg spacecraft/payload to send to the Outer planets or beyond.  What could be achieved by SS?

There was a posting in Aug of 2019 about this, with references to "Starkicker", but the discussion didn't get very far:
https://forum.nasaspaceflight.com/index.php?topic=48722.msg1974023#msg1974023


Offline 50_Caliber

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Re: Starship for outer planets and beyond
« Reply #1 on: 06/14/2020 01:30 am »
For interstellar missions, I would think you would use starship to loft a large VASIMR engine and possibly a another launch with a 100kw + class of solar panels. Have this engage it's VASIMR engines in a long arc around the sun as it powers the VASIMR engine and gains a lot of velocity. Then it would separate with an ion stage powered by your best Stirling Isotope Generator with complimentary battery packs that could charge and discharge for thrust pulses of the ion drive.

Even after all of the best propulsion/power tech with gravitational assist helping out (perhaps a Jupiter gravity assist) we might get about 100Km/sec this is blazingly fast, yet woefully short of any reasonable timeline to even the nearest star.

Ok, forget that, let's use Starship to build a laser-powered sail network, or wait until we have a practical fusion drive.  :P

Offline Ionmars

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Re: Starship for outer planets and beyond
« Reply #2 on: 06/14/2020 01:46 am »
Perhaps we need to turn the question backwards around. We set forth the destination, whether unmanned or robotic, and minimum time we will allow for the trip. Also what we will do when we get there. Then we might ask “Can Starship do this?"
« Last Edit: 06/14/2020 01:48 am by Ionmars »

Offline spacenut

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Re: Starship for outer planets and beyond
« Reply #3 on: 06/14/2020 01:51 am »
Solar power will not be very good past Mars.  However, Starship could launch small nuclear reactors to power Vasimr type engines to assemble a larger spacecraft. 

Another option is to have an orbiting fuel depot at Mars.  Martian Starships could launch fuel made on Mars for another Starship to travel to the Asteroid belt. 

A Starship could go and orbit Venus and drop sensors down into the atmosphere to do some atmospheric studies. 

Going back to a very large Starship Enterprise type spacecraft with artificial gravity.  Starships could assemble a larger spacecraft that is nuclear powered for travel, not only to the asteroid belt, but to the moons of Jupiter and Saturn.  Some of those moons have resources for refueling a larger ship with propellant for a large cluster of Vasimr type engines, and for water and oxygen replenishment for the spaceship. 

Mars could be used for a jump off point to Ceres.  Ceres a jump off point for Jupiters moons and so on. 

Large nuclear powered Ion type propulsion will probably be the only way to travel past Mars or Ceres. 

Offline Zed_Noir

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Re: Starship for outer planets and beyond
« Reply #4 on: 06/14/2020 09:07 am »
<snip>
Large nuclear powered Ion type propulsion will probably be the only way to travel past Mars or Ceres.

Ain't you forgetting the Project Orion propulsion system. Otherwise known as the nuclear pulse drive with multiple mini tac nukes.

Just mounted the Starship in front of the blast shield/push structure.

Of course people might object to multiple fission detonations needed to make the drive work.

Offline _MECO

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Re: Starship for outer planets and beyond
« Reply #5 on: 06/14/2020 09:36 am »
For interstellar missions, I would think you would use starship to loft a large VASIMR engine and possibly a another launch with a 100kw + class of solar panels. Have this engage it's VASIMR engines in a long arc around the sun as it powers the VASIMR engine and gains a lot of velocity. Then it would separate with an ion stage powered by your best Stirling Isotope Generator with complimentary battery packs that could charge and discharge for thrust pulses of the ion drive.

Even after all of the best propulsion/power tech with gravitational assist helping out (perhaps a Jupiter gravity assist) we might get about 100Km/sec this is blazingly fast, yet woefully short of any reasonable timeline to even the nearest star.

Ok, forget that, let's use Starship to build a laser-powered sail network, or wait until we have a practical fusion drive.  :P

Isn't the whole gist of VASIMR that you can switch between high thrust/low Isp and low thrust/high Isp? Surely if you're embarking on an interstellar mission you would want to go the high Isp route only, and at that point you could design a novel engine which trades versatility for efficiency. I would imagine that an expendable Starship could, in conjunction with multiple gravity assists, kick such a vehicle on a hard enough escape trajectory that you wouldn't even need to think about gravity losses from the Sun. The ideal engine's exhaust might almost more resemble a charged particle beam than a spew of plasma, if you only really cared about specific impulse, don't you think?

Offline steveleach

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Re: Starship for outer planets and beyond
« Reply #6 on: 06/14/2020 10:54 am »
You could also use a pyramid of Starships.

Eight fully-fuelled expendable Starships leave Earth orbit. After burning half their fuel, four of them transfer what's left to the other four (filling them up). Those 4 burn half their fuel, then 2 refuel the other 2. Those burn half their fuel and one transfers to the final one.

If that doesn't give you enough delta-v then add another layer of 16 Starships at the base of the pyramid; if that's not enough add another layer of 32.

Each layer in the pyramid doubles the cost of the mission, and adds a fixed amount of delta-v (half the dv of a fully-fuelled expendable Starship), so it gets expensive, fast. That said, New Horizons cost $700m, which would pay for 16 Starships at 30 million each plus 96 tanker launches at 2 million each.

Assuming 9km/s delta-v for a Starship, that is...

1 SS : 9 km/s
2 SS : 4.5 + 9 km/s = 13.5km/s
4 SS : 4.5 + 4.5 + 9 km/s = 18 km/s
8 SS : 4.5 + 4.5 + 4.5 + 9 km/s = 22.5 km/s
16 SS : 4.5 + 4.5 + 4.5 + 4.5 + 9 km/s = 27 km/s

That's about as fast as Voyager 1 got to with all its gravity assists, just from Starship, and within a matter of hours.

If you have that final Starship launch a nuclear-electric probe, and have it do its own gravity assists, you could give that probe a pretty high final velocity. 

Offline catiare

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Starship for outer planets and beyond
« Reply #7 on: 06/14/2020 11:57 am »
How about replacing the raptor engines & tanks with a Nuclear Salt Water engine?

http://www.projectrho.com/public_html/rocket/enginelist2.php#nswr

“... Zubrin then goes on to speculate about a more advanced version of the NSWR, suitable for insterstellar travel. Say that the 2% uranium bromide solution used uranium enriched to 90% U235 instead of only 20%. Assume that the fission yield was 90% instead of 0.1%. And assume a nozzle efficency of 0.9 instead of 0.8.

That would result in an exhaust velocity of a whopping 4,725,000 m/s (about 1.575% c, a specific impulse of 482,140 seconds). In a ship with a mass ratio of 10, it would have a delta V of 3.63% c. Now you're talkin...”

That combined with some Hibernation technology for the crew:

http://www.projectrho.com/public_html/rocket/humanfactor.php#id--Suspended_Animation

We can now plan a trip to Proxima Centauri!
« Last Edit: 06/14/2020 04:11 pm by catiare »


Offline Nomadd

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Re: Starship for outer planets and beyond
« Reply #9 on: 06/14/2020 12:58 pm »
Two relevant tweets from Elon:

https://twitter.com/elonmusk/status/1111760133132947458

https://twitter.com/elonmusk/status/1111798912141017089
I think Tim needs to look up the price for those kick stages. It seems insane that they could cost more than an entire Starship, but it's going to take a while for the new reality to work it's way through the system.
 I just hope they don't accidentally travel back in time with that extreme maneuver.
« Last Edit: 06/14/2020 12:59 pm by Nomadd »
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Offline rakaydos

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Re: Starship for outer planets and beyond
« Reply #10 on: 06/14/2020 01:07 pm »
There's the full DV in an oberth burn from earth C3

There's refueling in interplanetary space and oberthing in the Jovian Slingshot

and there's refueliing (with refuelded tankers) and burning at periapse in what XKCD called the "Kepler/Oberth maneuver" ("It works in KSP!"), possibly with a solar sail deployed just after solar periapse.

Offline 50_Caliber

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Re: Starship for outer planets and beyond
« Reply #11 on: 06/14/2020 01:19 pm »
For interstellar missions, I would think you would use starship to loft a large VASIMR engine and possibly a another launch with a 100kw + class of solar panels. Have this engage it's VASIMR engines in a long arc around the sun as it powers the VASIMR engine and gains a lot of velocity. Then it would separate with an ion stage powered by your best Stirling Isotope Generator with complimentary battery packs that could charge and discharge for thrust pulses of the ion drive.

Even after all of the best propulsion/power tech with gravitational assist helping out (perhaps a Jupiter gravity assist) we might get about 100Km/sec this is blazingly fast, yet woefully short of any reasonable timeline to even the nearest star.

Ok, forget that, let's use Starship to build a laser-powered sail network, or wait until we have a practical fusion drive.  :P

Isn't the whole gist of VASIMR that you can switch between high thrust/low Isp and low thrust/high Isp? Surely if you're embarking on an interstellar mission you would want to go the high Isp route only, and at that point you could design a novel engine which trades versatility for efficiency. I would imagine that an expendable Starship could, in conjunction with multiple gravity assists, kick such a vehicle on a hard enough escape trajectory that you wouldn't even need to think about gravity losses from the Sun. The ideal engine's exhaust might almost more resemble a charged particle beam than a spew of plasma, if you only really cared about specific impulse, don't you think?
VASIMR is a pretty capable propulsion technology and may be enough for all of the thrust, I think it's main drawback is that it requires a lot of power which would be massive. Depending on which performance parameters you believe, the more advanced ion drives can surpass it's ISP with less thrust. I will leave that up to those more knowledgeable than me to sort out the best configuration for high speed travel. I suspect there are tradeoffs for whichever configuration you choose.

Offline philw1776

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Re: Starship for outer planets and beyond
« Reply #12 on: 06/14/2020 02:05 pm »
VASIMR reminds me of Virgin Galactic.  Decades of effort. Minimal to zero actual flight operation.
No viable power sources under development, and IF they existed, cooling the fantasized very large megawatt spaceflight capable reactors adds lots of dead mass.  Ion thrusters are wimpy but deliver far more capability per Kw. And they have flown.
FULL SEND!!!!

Offline Ionmars

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Re: Starship for outer planets and beyond
« Reply #13 on: 06/14/2020 03:33 pm »
Background reading on some advanced engines that might be considered for upper stages of Starship (SS or SH):

Plasma engines/VASIMR
https://forum.nasaspaceflight.com/index.php?topic=34788.0

Nuclear Thermal Propulsion (NTR)
https://forum.nasaspaceflight.com/index.php?topic=50188.0

 Integrated Structural Electrodynamic Propulsion (ISEP)
https://forum.nasaspaceflight.com/index.php?topic=50188.0

 Pulsed fission nuclear thermal propulsion
https://forum.nasaspaceflight.com/index.php?topic=46642.0

Offline _MECO

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Re: Starship for outer planets and beyond
« Reply #14 on: 06/14/2020 04:36 pm »
For interstellar missions, I would think you would use starship to loft a large VASIMR engine and possibly a another launch with a 100kw + class of solar panels. Have this engage it's VASIMR engines in a long arc around the sun as it powers the VASIMR engine and gains a lot of velocity. Then it would separate with an ion stage powered by your best Stirling Isotope Generator with complimentary battery packs that could charge and discharge for thrust pulses of the ion drive.

Even after all of the best propulsion/power tech with gravitational assist helping out (perhaps a Jupiter gravity assist) we might get about 100Km/sec this is blazingly fast, yet woefully short of any reasonable timeline to even the nearest star.

Ok, forget that, let's use Starship to build a laser-powered sail network, or wait until we have a practical fusion drive.  :P

Isn't the whole gist of VASIMR that you can switch between high thrust/low Isp and low thrust/high Isp? Surely if you're embarking on an interstellar mission you would want to go the high Isp route only, and at that point you could design a novel engine which trades versatility for efficiency. I would imagine that an expendable Starship could, in conjunction with multiple gravity assists, kick such a vehicle on a hard enough escape trajectory that you wouldn't even need to think about gravity losses from the Sun. The ideal engine's exhaust might almost more resemble a charged particle beam than a spew of plasma, if you only really cared about specific impulse, don't you think?
VASIMR is a pretty capable propulsion technology and may be enough for all of the thrust, I think it's main drawback is that it requires a lot of power which would be massive. Depending on which performance parameters you believe, the more advanced ion drives can surpass it's ISP with less thrust. I will leave that up to those more knowledgeable than me to sort out the best configuration for high speed travel. I suspect there are tradeoffs for whichever configuration you choose.

Well, VASIMR is similar to any special-built thruster like I described in that it's a Magnetoplasmadynamic thruster. They theoretically even could exceed ion engines in their Isp, but like you said they require massive amounts of power- as in, fusion or massive fission plant amounts of power.

These are concepts vastly outside the scope of debate surrounding Starship at the moment. In fact I think the "beyond" part of this thread's title of "outer planets and beyond" threatens to have it moved over to the crackpot "advanced concepts" board. Starship could reasonably loft a probe on an escape trajectory from the Solar System or carry a payload to Saturn, but those are already fringe applications for the vehicle.

 If you're talking about a destination and using light years as a unit for travel distances, maybe discussion shouldn't be directly centered on the Earth/Moon/Mars transport system. How about a friendly discussion of manned ISRU plants on Ceres or Callisto or something? That would be more within reason, I think.

Offline Eka

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Re: Starship for outer planets and beyond
« Reply #15 on: 06/14/2020 04:55 pm »
Two relevant tweets from Elon:

https://twitter.com/elonmusk/status/1111760133132947458

https://twitter.com/elonmusk/status/1111798912141017089
I think Tim needs to look up the price for those kick stages. It seems insane that they could cost more than an entire Starship, but it's going to take a while for the new reality to work it's way through the system.
 I just hope they don't accidentally travel back in time with that extreme maneuver.
Not much more effort to make another stage with 3 or 4 such Starkickers strapped together pushing the Starkicker like EM mentioned. The cost is peanuts.

I can see Starkickers being designed to be quickly stripped of excess mass in orbit. Make the skirt and faring retractable pin removable. Gimbal the Vacuum Raptors. Launch into orbit with no load & refuel so no SL Raptors need to be mounted and removed. Remove fairings, and skirts. Join together using a thrust frame between the first stage set, and the second stage one. Maybe use another Starship to boost into a highly elliptical orbit.

The joint between the skirt and main body can be a U on the skirt with a edge that slots down into the U. The joint would circle the whole bottom of the tank/skirt interface allowing even thrust transfer. Retractable pins then hold it together during launch, and refueling.

The faring can use the same type of joint.

The framework to allow thrust transfer between the 3 or 4 first stages and the second stage obviously uses the same joints. The hard part is figuring out a design that allows it to be lofted folded up inside a regular Starship faring.

Yeah, a purpose built first stage would be better, but that would cost a lot more engineering.

Oh, all of you thinking external blast type nuke propulsion are viable, EMP pulses in near earth orbit are a Titanic level no no. All craft powered with those types of engines must be moved far away from earth before being lit up. BTW, it isn't just the EMP pulses that are an issue. The plasma from them will also cause serious issues.
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Offline Bob Shaw

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Re: Starship for outer planets and beyond
« Reply #16 on: 06/14/2020 07:17 pm »
Solar sails can get up to seriously high speeds, especially if they are big ones. They can also be used to reflect and concentrate very weak sunlight on PV panels. IIRC I saw a paper on this years back, and it was remarkable what you could do.

Offline catiare

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Re: Starship for outer planets and beyond
« Reply #17 on: 06/14/2020 08:24 pm »
I still believe the best option is take the guts out of a starship and replace it with an NSWR engine. Below is a refreshed article. It claims earth to jupiter in about 10 days.   

https://www.linkedin.com/pulse/20140724165847-39571567-nuclear-salt-water-rockets-revisited/

Offline Lemurion

Re: Starship for outer planets and beyond
« Reply #18 on: 06/14/2020 09:50 pm »
I still believe the best option is take the guts out of a starship and replace it with an NSWR engine. Below is a refreshed article. It claims earth to jupiter in about 10 days.   

https://www.linkedin.com/pulse/20140724165847-39571567-nuclear-salt-water-rockets-revisited/

The science fiction fan in me LOVES NSWR engines and has for years: high thrust and high ISP; it's almost magical.

At the same time, the more grounded space enthusiast takes one look at the political and environmental hurdles involved in flying one and says there's no way in Hell anyone's ever going to get the go-ahead to even do a serious design study, let alone fly one.


Offline SteveJ

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Re: Starship for outer planets and beyond
« Reply #19 on: 06/14/2020 11:53 pm »
While VASIMR, NSWR, and similar technologies are very interesting, I was hoping to concentrate the discussion on what can be done with the technology SpaceX has now, or is likely to have in the next 5 years.  For instance, what can be done by carrying extra fuel tanks for just the SS itself, a boost stage(s) from Raptor methane/LOX engines or Draco/Super Draco engines, or combinations therein.  It could include building a custom version of the SS, as long as it didn't depart tremendously from the available technology.

The assumption would be to perform the boost within the Earth's gravity well (Oberth maneuver), and a gravity assist by Jupiter.  With the kind of mass SS could lift, it might be worth dedicating the mass needed to thermally shield the spacecraft for an Oberth maneuver near the sun.

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