5 ms·

Probably is no breakthrough, other than solving a common problem with a reusable approach. It is wasteful to have every satellite carry the weight of its own p

by gibolt 7y ago

Probably is no breakthrough, other than solving a common problem with a reusable approach. It is wasteful to have every satellite carry the weight of its own propellant and engines. Having a single device that can deliver quite a few satellites to their orbit through clever planning and efficient fuel use could save significantly on weight, design, and launch, costs and complexity.

cbanek 7y ago
Well delivering multiple satellites could be a thing, it's still basically the same cost by mass, you're just splitting the monetary cost up among different customers. If you are delivering multiple GEO satellites, you also have to have them be the right place in their orbit, over their target, since they are stationary with respect to the earth (which is why you don't have to move your satellite TV dish). This means all your satellites for that bunch have to basically be near each other. That also doesn't feel like it is reusable given this definition. I'd assume reusable means you can use it now, and then use it next month on a completely different mission. So let's explore that. GEO satellites are also generally a lot bigger than your typical cubesat / nanosats that are all the rage in the bulk launcher configurations, because you need a big dish, and a lot of power to transmit and receive signals. > It is wasteful to have every satellite carry the weight of its own propellant and engines. Even if a satellite was delivered to GEO without using an engine, satellites need engines to do stationkeeping and keep their orbit, which is the critical factor for the operational lifetime of a satellite. It's more wasteful to have to have your orbiting tug do an orbital rendezvous with a satellite in LEO (takes fuel to rendezvous), go to GEO (the normal cost, but more expensive since you have to carry the fuel for the return trip), then come back from GEO to LEO (takes fuel). Following this delta-v map, it looks like it takes about 4000m/s of delta-v to go from LEO to GEO, then the same the other way back down. https://external-preview.redd.it/U5iH7huE5qKth7ZFvipXt8vzaFOO99qHFh9o9_SkLLk.png?auto=webp&s=d145ac9ae496abe35fae86fc11a584d62fe42592 https://external-preview.redd.it/U5iH7huE5qKth7ZFvipXt8vzaFO... I don't know of any clever planning or efficient fuel use that can get over the raw amount of delta-v you'd need. Fuel use isn't really efficient, it's the engine that has to efficiently use the fuel, which is why I think there must be some breakthrough here. Fuel also has to eventually be delivered up to the tug for refuel, so really it seems like all the mass savings is the dry mass of the 3rd stage.
- branchan 7y ago
  I totally agree. You still need to get the fuel to space regardless of who is doing the propulsion work. Let's say that your tug is already on-orbit, how is the fuel going to be brought up? Would you not need to launch another spacecraft to bring you the fuel? How much would that spacecraft weigh? Besides this, they would have to develop on-orbit refueling technology, as well as force the other spacecraft to use a bus that allows for rendez-vous and docking/proximity ops. And also, how big is the market for satellite startups that are heading to GEO orbit? For now, it seems like it is just Astranis and GapSat.
  - ibmont 7y ago
    We will be able to transport satellites up to 5000 lb in mass directly to GEO, which should be most of the market. Almost every large GEO player is developing new, smaller satellites. We will also modify existing interfaces to allow for docking. Rendezvous and prox-ops is all on our side.
    - branchan 7y ago
      Who is "we"? Care to identify yourself? What existing interface are you talking about? Which GEO manufacturer is making 5000 lb spacecraft?
      - zarathustra10 7y ago
        I can take a wild guess who "we" is, since Epic's young founder is Ignacio B. Montero and the nick is "ibmont".
        ibmont 7y ago
        "you got me"
- ibmont 7y ago
  That you don't know of it doesn't mean it doesnt exist :)

by gibolt 7y ago

cbanek 7y ago

Well delivering multiple satellites could be a thing, it's still basically the same cost by mass, you're just splitting the monetary cost up among different customers. If you are delivering multiple GEO satellites, you also have to have them be the right place in their orbit, over their target, since they are stationary with respect to the earth (which is why you don't have to move your satellite TV dish). This means all your satellites for that bunch have to basically be near each other. That also doesn't feel like it is reusable given this definition. I'd assume reusable means you can use it now, and then use it next month on a completely different mission. So let's explore that. GEO satellites are also generally a lot bigger than your typical cubesat / nanosats that are all the rage in the bulk launcher configurations, because you need a big dish, and a lot of power to transmit and receive signals. > It is wasteful to have every satellite carry the weight of its own propellant and engines. Even if a satellite was delivered to GEO without using an engine, satellites need engines to do stationkeeping and keep their orbit, which is the critical factor for the operational lifetime of a satellite. It's more wasteful to have to have your orbiting tug do an orbital rendezvous with a satellite in LEO (takes fuel to rendezvous), go to GEO (the normal cost, but more expensive since you have to carry the fuel for the return trip), then come back from GEO to LEO (takes fuel). Following this delta-v map, it looks like it takes about 4000m/s of delta-v to go from LEO to GEO, then the same the other way back down. https://external-preview.redd.it/U5iH7huE5qKth7ZFvipXt8vzaFOO99qHFh9o9_SkLLk.png?auto=webp&s=d145ac9ae496abe35fae86fc11a584d62fe42592 https://external-preview.redd.it/U5iH7huE5qKth7ZFvipXt8vzaFO... I don't know of any clever planning or efficient fuel use that can get over the raw amount of delta-v you'd need. Fuel use isn't really efficient, it's the engine that has to efficiently use the fuel, which is why I think there must be some breakthrough here. Fuel also has to eventually be delivered up to the tug for refuel, so really it seems like all the mass savings is the dry mass of the 3rd stage.

branchan 7y ago
I totally agree. You still need to get the fuel to space regardless of who is doing the propulsion work. Let's say that your tug is already on-orbit, how is the fuel going to be brought up? Would you not need to launch another spacecraft to bring you the fuel? How much would that spacecraft weigh? Besides this, they would have to develop on-orbit refueling technology, as well as force the other spacecraft to use a bus that allows for rendez-vous and docking/proximity ops. And also, how big is the market for satellite startups that are heading to GEO orbit? For now, it seems like it is just Astranis and GapSat.
- ibmont 7y ago
  We will be able to transport satellites up to 5000 lb in mass directly to GEO, which should be most of the market. Almost every large GEO player is developing new, smaller satellites. We will also modify existing interfaces to allow for docking. Rendezvous and prox-ops is all on our side.
  - branchan 7y ago
    Who is "we"? Care to identify yourself? What existing interface are you talking about? Which GEO manufacturer is making 5000 lb spacecraft?
    - zarathustra10 7y ago
      I can take a wild guess who "we" is, since Epic's young founder is Ignacio B. Montero and the nick is "ibmont".
      - ibmont 7y ago
        "you got me"
ibmont 7y ago
That you don't know of it doesn't mean it doesnt exist :)