---
type: claim
domain: space-development
description: "A large training run on tens of thousands of GPUs needs constant all-to-all gradient exchange at hundreds of Tbps — current satellite links deliver 200 Gbps per node with next-gen targeting 1 Tbps making orbital training likely never viable"
confidence: likely
source: "Astra, space data centers feasibility analysis February 2026; Google Project Suncatcher analysis"
created: 2026-02-17
depends_on:
  - "distributed LEO inference networks could serve global AI requests at 4-20ms latency competitive with centralized terrestrial data centers for latency-tolerant workloads"
  - "space-based computing at datacenter scale is blocked by thermal physics because radiative cooling in vacuum requires surface areas that grow faster than compute density"
---

# Orbital AI training is fundamentally incompatible with space communication links because distributed training requires hundreds of Tbps aggregate bandwidth while orbital links top out at single-digit Tbps

Large-scale AI training is the one workload that virtually every serious analysis concludes will never move to orbit. The reason is bandwidth, and the gap is not marginal -- it is orders of magnitude.

Training a frontier model involves distributing computation across tens of thousands of GPUs that must constantly exchange gradient updates during backpropagation. This requires aggregate inter-node bandwidth measured in hundreds of terabits per second with tight synchronization (microsecond-scale consistency across nodes). A single terrestrial data center typically has 100-plus Tbps of aggregate internal bandwidth, with individual node interconnects running at 400 Gbps to 800 Gbps (moving toward 1.6 Tbps with next-generation InfiniBand and Ethernet standards).

Current state-of-the-art satellite communication links deliver: Starlink satellites at 200 Gbps per satellite with next generation targeting 1 Tbps; Blue Origin TeraWave at up to 6 Tbps; Axiom optical inter-satellite links at 10 Gbps. Even Blue Origin's most ambitious specification falls two orders of magnitude short of the aggregate bandwidth a terrestrial training cluster provides.

The bandwidth constraint is compounded by latency jitter. Distributed training algorithms (data parallelism, model parallelism, pipeline parallelism) all require deterministic communication timing to maintain training efficiency. Orbital link latency varies with satellite position, atmospheric conditions on ground links, and inter-satellite hop count -- introducing jitter that degrades training throughput even when average bandwidth is sufficient.

Starcloud's demonstration of "training an LLM in space" almost certainly involved a small model on a single GPU -- a valid proof of concept for orbital hardware operation but not evidence that distributed training at frontier scale is feasible. This constraint shapes the entire orbital compute opportunity: inference yes (eventually), on-orbit satellite processing yes (now), training no (likely never).

## Evidence
- Terrestrial data center aggregate bandwidth: 100+ Tbps with 400-800 Gbps per node
- Starlink satellite links: 200 Gbps current, 1 Tbps next-gen target
- Blue Origin TeraWave: up to 6 Tbps (most ambitious orbital link)
- Gap: 2+ orders of magnitude between orbital and terrestrial bandwidth

## Challenges
Novel training algorithms that reduce communication requirements (local SGD, federated learning approaches) could narrow the gap, but the fundamental bandwidth asymmetry makes orbital training uncompetitive for frontier-scale models.

---

Relevant Notes:
- [[distributed LEO inference networks could serve global AI requests at 4-20ms latency competitive with centralized terrestrial data centers for latency-tolerant workloads]] — inference works because it does not require all-to-all bandwidth
- [[on-orbit processing of satellite data is the proven near-term use case for space compute because it avoids bandwidth and thermal bottlenecks simultaneously]] — the viable alternative to moving training to orbit

Topics:
- [[space exploration and development]]
